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For years, I believed that drag-and-drop games — especially those involving rotation, spatial logic, and puzzle solving — were the exclusive domain of JavaScript. Until one day, I asked AI:

“Is it possible to build a fully interactive Tangram puzzle game using only CSS?”

The answer: “No — not really. You’ll need JavaScript.” That was all the motivation I needed to prove otherwise.

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But first, let’s ask the obvious question: Why would anyone do this?

Well…

• To know how far CSS can be pushed in creating interactive UIs.
• To get better at my CSS skills.
• And it’s fun!

Fair enough?

Now, here’s the unsurprising truth: CSS isn’t exactly made for this. It’s not a logic language, and let’s be honest, it’s not particularly dynamic either. (Sure, we have CSS variables and some handy built-in functions now, hooray!)

In JavaScript, we naturally think in terms of functions, loops, conditions, objects, comparisons. We write logic, abstract things into methods, and eventually ship a bundle that the browser understands. And once it’s shipped? We rarely look at that final JavaScript bundle — we just focus on keeping it lean.

Now ask yourself: isn’t that exactly what Sass does for CSS?

Why should we hand-write endless lines of repetitive CSS when we can use mixins and functions to generate it — cleanly, efficiently, and without caring how many lines it takes, as long as the output is optimized?

So, we put it to the test and it turns out Sass can replace JavaScript, at least when it comes to low-level logic and puzzle behavior. With nothing but maps, mixins, functions, and a whole lot of math, we managed to bring our Tangram puzzle to life, no JavaScript required.

Let the (CSS-only) games begin! 🎉

The game

The game consists of seven pieces: the classic Tangram set. Naturally, these pieces can be arranged into a perfect square (and many other shapes, too). But we need a bit more than just static pieces.

So here’s what I am building:

• A puzzle goal, which is the target shape the player has to recreate.
• A start button that shuffles all the pieces into a staging area.
• Each piece is clickable and interactive.
• The puzzle should let the user know when they get a piece wrong and also celebrate when they finish the puzzle.

The HTML structure

I started by setting up the HTML structure, which is no small task, considering the number of elements involved.

• Each shape was given seven radio buttons. I chose radios over checkboxes to take advantage of their built-in exclusivity. Only one can be selected within the same group. This made it much easier to track which shape and state were currently active.
• The start button? Also a radio input. A checkbox could’ve worked too, but for the sake of consistency, I stuck with radios across the board.
• The puzzle map itself is just a plain old <div>, simple and effective.
• For rotation, we added eight radio buttons, each representing a 45-degree increment: 45°, 90°, 135°, all the way to 360°. These simulate rotation controls entirely in CSS.
• Every potential shadow position got its own radio button too. (Yes, it’s a lot, I know.)
• And to wrap it all up, I included a classic reset button inside a <form> using <button type="reset">, so players can easily start over at any point.

Given the sheer number of elements required, I used Pug to generate the HTML more efficiently. It was purely a convenience choice. It doesn’t affect the logic or behavior of the puzzle in any way.

Below is a sample of the compiled HTML. It might look overwhelming at first glance (and this is just a portion of it!), but it illustrates the structural complexity involved. This section is collapsed to not nuke your screen, but it can be expanded if you’d like to explore it.

Open HTML Code <div class="wrapper"> <div class="tanagram-box"></div> <div class="tanagram-box"></div> <form class="container"> <input class="hide_input start" type="checkbox" id="start" autofocus /> <button class="start-button" type="reset" id="restart">Restart</button> <label class="start-button" for="start">Start </label> <div class="shadow"> <input class="hide_input" type="radio" id="blueTriangle-tan" name="tan-active" /> <input class="hide_input" type="radio" id="yellowTriangle-tan" name="tan-active" /> <!-- Inputs for others tans --> <input class="hide_input" type="radio" id="rotation-reset" name="tan-active" /> <input class="hide_input" type="radio" id="rotation-45" name="tan-rotation" /> <input class="hide_input" type="radio" id="rotation-90" name="tan-rotation" /> <!--radios for 90, 225, 315, 360 --> <input class="hide_input" type="checkbox" id="yellowTriangle-tan-1-135" name="tan-rotation" /> <input class="hide_input" type="checkbox" id="yellowTriangle-tan-1-225" name="tan-rotation" /> <!-- radio for every possible shape shadows--> <label class="rotation rot" for="rotation-45" id="rot45">⟲</label> <label class="rotation rot" for="rotation-90" id="rot90">⟲</label> <!--radios for 90, 225, 315, 360 --> <label class="rotation" for="rotation-reset" id="rotReset">✘</label> <label class="blueTriangle tans" for="blueTriangle-tan" id="tanblueTrianglelab"></label> <div class="tans tan_blocked" id="tanblueTrianglelabRes"></div> <!-- labels for every tan and disabled div --> <label class="blueTriangle tans" for="blueTriangle-tan-1-90" id="tanblueTrianglelab-1-90"></label> <label class="blueTriangle tans" for="blueTriangle-tan-1-225" id="tanblueTrianglelab-1-225"></label> <!-- labels radio for every possible shape shadows--> <div class="shape"></div> </div> </form> <div class="tanagram-box"></div> <div class="tanagram-box"></div> <div class="tanagram-box"></div> <div class="tanagram-box"></div> <div class="tanagram-box"></div> </div> Creating maps for shape data

Now that HTML skeleton is ready, it’s time to inject it with some real power. That’s where our Sass maps come in, and here’s where the puzzle logic starts to shine.

Note: Maps in Sass hold pairs of keys and values, and make it easy to look up a value by its corresponding key. Like objects in JavaScript, dictionaries in Python and, well, maps in C++.

I’m mapping out all the core data needed to control each tangram piece (tan): its color, shape, position, and even interaction logic. These maps contain:

• the background-color for each tan,
• the clip-path coordinates that define their shapes,
• the initial position for each tan,
• the position of the blocking div (which disables interaction when a tan is selected),
• the shadow positions (coordinates for the tan’s silhouette displayed on the task board),
• the grid information, and
• the winning combinations — the exact target coordinates for each tan, marking the correct solution.

$colors: ( blue-color: #53a0e0, yellow-color: #f7db4f, /* Colors for each tan */ ); $nth-child-grid: ( 1: (2, 3, 1, 2, ), 2: ( 3, 4, 1, 2, ), 4: ( 1, 2, 2, 3, ), /* More entries to be added */); $bluePosiblePositions: ( 45: none, 90: ( (6.7, 11.2), ), 135: none, 180: none, /* Positions defined up to 360 degrees */); /* Other tans */ /* Data defined for each tan */ $tansShapes: ( blueTriangle: ( color: map.get($colors, blue-color), clip-path: ( 0 0, 50 50, 0 100, ), rot-btn-position: ( -20, -25, ), exit-mode-btn-position: ( -20, -33, ), tan-position: ( -6, -37, ), diable-lab-position: ( -12, -38, ), poss-positions: $bluePosiblePositions, correct-position: ((4.7, 13.5), (18.8, 13.3), ), transform-origin: ( 4.17, 12.5,), ), ); /* Remaining 7 combinations */ $winningCombinations: ( combo1: ( (blueTriangle, 1, 360), (yellowTriangle, 1, 225), (pinkTriangle, 1, 180), (redTriangle, 4, 360), (purpleTriangle, 2, 225), (square, 1, 90), (polygon, 4, 90), ), );

You can see this in action on CodePen, where these maps drive the actual look and behavior of each puzzle piece. At this point, there’s no visible change in the preview. We’ve simply prepared and stored the data for later use.

CodePen Embed Fallback Using mixins to read from maps

The main idea is to create reusable mixins that will read data from the maps and apply it to the corresponding CSS rules when needed.

But before that, we’ve elevated things to a higher level by making one key decision: We never hard-coded units directly inside the maps. Instead, we built a reusable utility function that dynamically adds the desired unit (e.g., vmin, px, etc.) to any numeric value when it’s being used. This way, when can use our maps however we please.

@function get-coordinates($data, $key, $separator, $unit) { $coordinates: null; // Check if the first argument is a map @if meta.type-of($data) == "map" { // If the map contains the specified key @if map.has-key($data, $key) { // Get the value associated with the key (expected to be a list of coordinates) $coordinates: map.get($data, $key); } // If the first argument is a list } @else if meta.type-of($data) == "list" { // Ensure the key is a valid index (1-based) within the list @if meta.type-of($key) == "number" and $key > 0 and $key <= list.length($data) { // Retrieve the item at the specified index $coordinates: list.nth($data, $key); } // If neither map nor list, throw an error } @else { @error "Invalid input: First argument must be a map or a list."; } // If no valid coordinates were found, return null @if $coordinates == null { @return null; } // Extract x and y values from the list $x: list.nth($coordinates, 1); $y: list.nth($coordinates, -1); // -1 gets the last item (y) // Return the combined x and y values with units and separator @return #{$x}#{$unit}#{$separator}#{$y}#{$unit}; }

Sure, nothing’s showing up in the preview yet, but the real magic starts now.

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Now we move on to writing mixins. I’ll explain the approach in detail for the first mixin, and the rest will be described through comments.

The first mixin dynamically applies grid-column and grid-row placement rules to child elements based on values stored in a map. Each entry in the map corresponds to an element index (1 through 8) and contains a list of four values: [start-col, end-col, start-row, end-row].

@mixin tanagram-grid-positioning($nth-child-grid) { // Loop through numbers 1 to 8, corresponding to the tanam pieces @for $i from 1 through 8 { // Check if the map contains a key for the current piece (1-8) @if map.has-key($nth-child-grid, $i) { // Get the grid values for this piece: [start-column, end-column, start-row, end-row] $values: map.get($nth-child-grid, $i); // Target the nth child (piece) and set its grid positions &:nth-child(#{$i}) { // Set grid-column: start and end values based on the first two items in the list grid-column: #{list.nth($values, 1)} / #{list.nth($values, 2)}; // Set grid-row: start and end values based on the last two items in the list grid-row: #{list.nth($values, 3)} / #{list.nth($values, 4)}; } } } }

We can expect the following CSS to be generated:

.tanagram-box:nth-child(1) { grid-column: 2 / 3; grid-row: 1 / 2; } .tanagram-box:nth-child(2) { grid-column: 3 / 4; grid-row: 1 / 2; } CodePen Embed Fallback

In this mixin, my goal was actually to create all the shapes (tans). I am using clip-path. There were ideas to use fancy SVG images, but this test project is more about testing the logic rather than focusing on beautiful design. For this reason, the simplest solution was to cut the elements according to dimensions while they are still in the square (the initial position of all the tans).

So, in this case, through a static calculation, the $tansShapes map was updated with the clip-path property:

clip-path: (0 0, 50 50, 0 100);

This contains the clip points for all the tans. In essence, this mixin shapes and colors each tan accordingly.

@mixin set-tan-clip-path($tanName, $values) { // Initialize an empty list to hold the final clip-path points $clip-path-points: (); // Extract the 'clip-path' data from the map, which contains coordinate pairs $clip-path-key: map.get($values, clip-path); // Get the number of coordinate pairs to loop through $count: list.length($clip-path-key); // Loop through each coordinate point @for $i from 1 through $count { // Convert each pair of numbers into a formatted coordinate string with units $current-point: get-coordinates($clip-path-key, $i, " ", "%"); // Add the formatted coordinate to the list, separating each point with a comma $clip-path-points: list.append($clip-path-points, #{$current-point}, comma); } // Style for the preview element (lab version), using the configured background color #tan#{$tanName}lab { background: map.get($values, color); clip-path: polygon(#{$clip-path-points}); // Apply the full list of clip-path points } // Apply the same clip-path to the actual tan element .#{$tanName} { clip-path: polygon(#{$clip-path-points}); } }

and output in CSS should be:

.blueTriangle { clip-path: polygon(0% 0%, 50% 50%, 0% 100%); } /* other tans */ CodePen Embed Fallback Start logic

Alright, now I’d like to clarify what should happen first when the game loads.

First, with a click on the Start button, all the tans “go to their positions.” In reality, we assign them a transform: translate() with specific coordinates and a rotation.

.start:checked ~ .shadow #tanblueTrianglelab { transform-origin: 4.17vmin 12.5vmin; transform: translate(-6vmin,-37vmin) rotate(360deg); cursor: pointer; } CodePen Embed Fallback

So, we still maintain this pattern. We use transform and simply change the positions or angles (in the maps) of both the tans and their shadows on the task board.

When any tan is clicked, the rotation button appears. By clicking on it, the tan should rotate around its center, and this continues with each subsequent click. There are actually eight radio buttons, and with each click, one disappears and the next one appears. When we reach the last one, clicking it makes it disappear and the first one reappears. This way, we get the impression of clicking the same button (they are, of course, styled the same) and being able to click (rotate the tan) infinitely. This is exactly what the following mixin enables.

@mixin set-tan-rotation-states($tanName, $values, $angles, $color) { // This mixin dynamically applies rotation UI styles based on a tan's configuration. // It controls the positioning and appearance of rotation buttons and visual feedback when a rotation state is active. @each $angle in $angles{ & ~ #rot#{$angle}{ transform: translate(get-coordinates($values,rot-btn-position,',',vmin )); background: $color;} & ~ #rotation-#{$angle}:checked{ @each $key in map.keys($tansShapes){ & ~ #tan#{$key}labRes{ visibility: visible; background:rgba(0,0,0,0.4); } & ~ #tan#{$key}lab{ opacity:.3; } & ~ #rotReset{ visibility: visible; } } } } }

And the generated CSS should be:

#blueTriangle-tan:checked ~ #rotation-45:checked ~ #tanblueTrianglelab { transform: translate(-6vmin,-37vmin) rotate(45deg); } #blueTriangle-tan:checked ~ #rotation-45:checked ~ #tanblueTrianglelabRes { visibility: hidden; }

OK, the following mixins use the set-clip-path and set-rotation mixins. They contain all the information about the tans and their behavior in relation to which tan is clicked and which rotation is selected, as well as their positions (as defined in the second mixin).

@mixin generate-tan-shapes-and-interactions($tansShapes) { // Applies styling logic and UI interactions for each individual tan shape from the $tansShapes map. @each $tanName, $values in $tansShapes{ $color: color.scale(map.get($values, color), $lightness: 10%); $angles: (45, 90, 135, 180, 225, 270, 315, 360); @include set-tan-clip-path($tanName, $values); ##{$tanName}-tan:checked{ & ~ #tan#{$tanName}Res{ visibility:hidden; } & ~ #tan#{$tanName}lab{opacity: 1 !important;background: #{$color};cursor:auto;} @each $key in map.keys($tansShapes){ & ~ #tan#{$tanName}Res:checked ~ #tan#{$key}labRes{visibility: visible;} } & ~ #rot45{display: flex;visibility: visible;} & ~ #rotReset{ transform: translate(get-coordinates($values, exit-mode-btn-position,',', vmin)); } @include set-tan-rotation-states($tanName, $values, $angles, $color); } } } @mixin set-initial-tan-position($tansShapes) { // This mixin sets the initial position and transformation for both the interactive (`lab`) and shadow (`labRes`) versions // of each tan shape, based on coordinates provided in the $tansShapes map. @each $tanName, $values in $tansShapes{ & ~ .shadow #tan#{$tanName}lab{ transform-origin: get-coordinates($values, transform-origin,' ' ,vmin); transform: translate( get-coordinates($values,tan-position,',', vmin)) rotate(360deg) ; cursor: pointer; } & ~ .shadow #tan#{$tanName}labRes{ visibility:hidden; transform: translate(get-coordinates($values,diable-lab-position,',',vmin)); } } } CodePen Embed Fallback

As mentioned earlier, when a tan is clicked, one of the things that becomes visible is its shadow — a silhouette that appears on the task board.

These shadow positions (coordinates) are currently defined statically. Each shadow has a specific place on the map, and a mixin reads this data and applies it to the shadow using transform: translate().

When the clicked tan is rotated, the number of visible shadows on the task board can change, as well as their angles, which is expected.

Of course, special care was taken with naming conventions. Each shadow element gets a unique ID, made from the name (inherited from its parent tan) and a number that represents its sequence position for the given angle.

Pretty cool, right? That way, we avoid complicated naming patterns entirely!

@mixin render-possible-tan-positions( $name, $angle, $possiblePositions, $visibility, $color, $id, $transformOrigin ) { // This mixin generates styles for possible positions of a tan shape based on its name, rotation angle, and configuration map. // It handles both squares and polygons, normalizing their rotation angles accordingly and applying transform styles if positions exist.} @if $name == 'square' { $angle: normalize-angle($angle); // Normalizujemo ugao ako je u pitanju square } @else if $name == 'polygon'{ $angle: normalize-polygon-angle($angle); } @if map.has-key($possiblePositions, $angle) { $values: map.get($possiblePositions, $angle); @if $values != none { $count: list.length($values); @for $i from 1 through $count { $position: get-coordinates($values, $i, ',', vmin); & ~ #tan#{$name}lab-#{$i}-#{$angle} { @if $visibility == visible { visibility: visible; background-color: $color; opacity: .2; z-index: 2; transform-origin: #{$transformOrigin}; transform: translate(#{$position}) rotate(#{$angle}deg); } @else if $visibility == hidden { visibility: hidden; } &:hover{ opacity: 0.5; cursor: pointer; } } } } } }

The generated CSS:

#blueTriangle-tan:checked ~ #tanblueTrianglelab-1-360 { visibility: visible; background-color: #53a0e0; opacity: 0.2; z-index: 2; transform-origin: 4.17vmin 12.5vmin; transform: translate(4.7vmin,13.5vmin) rotate(360deg); }

This next mixin is tied to the previous one and manages when and how the tan shadows appear while their parent tan is being rotated using the button. It listens for the current rotation angle and checks whether there are any shadow positions defined for that specific angle. If there are, it displays them; if not — no shadows!

@mixin render-possible-positions-by-rotation { // This mixin applies rotation to each tan shape. It loops through each tan, calculates its possible positions for each angle, and handles visibility and transformation. // It ensures that rotation is applied correctly, including handling the transitions between various tan positions and visibility states. @each $tanName, $values in $tansShapes{ $possiblePositions: map.get($values, poss-positions); $possibleTansColor: map.get($values, color); $validPosition: get-coordinates($values, correct-position,',' ,vmin); $transformOrigin: get-coordinates($values,transform-origin,' ' ,vmin); $rotResPosition: get-coordinates($values,exit-mode-btn-position ,',' ,vmin ); $angle: 0; @for $i from 1 through 8{ $angle: $i * 45; $nextAngle: if($angle + 45 > 360, 45, $angle + 45); @include render-position-feedback-on-task($tanName,$angle, $possiblePositions,$possibleTansColor, #{$tanName}-tan, $validPosition,$transformOrigin, $rotResPosition); ##{$tanName}-tan{ @include render-possible-tan-positions($tanName,$angle, $possiblePositions,hidden, $possibleTansColor, #{$tanName}-tan,$transformOrigin) } ##{$tanName}-tan:checked{ @include render-possible-tan-positions($tanName,360, $possiblePositions,visible, $possibleTansColor, #{$tanName}-tan,$transformOrigin); & ~ #rotation-#{$angle}:checked { @include render-possible-tan-positions($tanName,360, $possiblePositions,hidden, $possibleTansColor, #{$tanName}-tan,$transformOrigin); & ~ #tan#{$tanName}lab{transform:translate( get-coordinates($values,tan-position,',', vmin)) rotate(#{$angle}deg) ;} & ~ #tan#{$tanName}labRes{ visibility: hidden; } & ~ #rot#{$angle}{ visibility: hidden; } & ~ #rot#{$nextAngle}{ visibility: visible } @include render-possible-tan-positions($tanName,$angle, $possiblePositions,visible, $possibleTansColor, #{$tanName}-tan,$transformOrigin); } } } } } CodePen Embed Fallback

When a tan’s shadow is clicked, the corresponding tan should move to that shadow’s position. The next mixin then checks whether this new position is the correct one for solving the puzzle. If it is correct, the tan gets a brief blinking effect and becomes unclickable, signaling it’s been placed correctly. If it’s not correct, the tan simply stays at the shadow’s location. There’s no effect and it remains draggable/clickable.

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Of course, there’s a list of all the correct positions for each tan. Since some tans share the same size — and some can even combine to form larger, existing shapes — we have multiple valid combinations. For this Camel task, all of them were taken into account. A dedicated map with these combinations was created, along with a mixin that reads and applies them.

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At the end of the game, when all tans are placed in their correct positions, we trigger a “merging” effect — and the silhouette of the camel turns yellow. At that point, the only remaining action is to click the Restart button.

Well, that was long, but that’s what you get when you pick the fun (albeit hard and lengthy) path. All as an ode to CSS-only magic!

Breaking Boundaries: Building a Tangram Puzzle With (S)CSS originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

The HTML popover attribute transforms elements into top-layer elements that can be opened and closed with a button or JavaScript. Most popovers can be light-dismissed, closing when the user clicks or taps outside the popup. Currently, HTML popover lacks built-in auto-close functionality, but it’s easy to add. Auto closing popups are useful for user interfaces like banner notifications — the new-message alerts in phones, for instance.

A picture demo, is worth a thousand words, right? Click on the “Add to my bookmarks” button in the following example. It triggers a notification that dismisses itself after a set amount of time.

CodePen Embed Fallback Let’s start with the popover

The HTML popover attribute is remarkably trivial to use. Slap it on a div, specify the type of popover you need, and you’re done.

<div popover="manual" id="pop">Bookmarked!</div>

A manual popover simply means it cannot be light-dismissed by clicking outside the element. As a result, we have to hide, show, or toggle the popover’s visibility ourselves explicitly with either buttons or JavaScript. Let’s use a semantic HTML button.

<button popovertarget="pop" popovertargetaction="show"> Add to my bookmarks </button> <div popover="manual" id="pop">Bookmarked!</div>

The popovertarget and popovertargetaction attributes are the final two ingredients, where popovertarget links the button to the popover element and popovertargetaction ensures that the popover is show-n when the button is clicked.

Hiding the popover with a CSS transition

OK, so the challenge is that we have a popover that is shown when a certain button is clicked, but it cannot be dismissed. The button is only wired up to show the popover, but it does not hide or toggle the popover (since we are not explicitly declaring it). We want the popover to show when the button is clicked, then dismiss itself after a certain amount of time.

The HTML popover can’t be closed with CSS, but it can be hidden from the page. Adding animation to that creates a visual effect. In our example, we will hide the popover by eliminating its CSS height property. You’ll learn in a moment why we’re using height, and that there are other ways you can go about it.

We can indeed select the popover attribute using an attribute selector:

[popover] { height: 0; transition: height cubic-bezier(0.6, -0.28, 0.735, 0.045) .3s .6s; @starting-style { height: 1lh; } }

When the popover is triggered by the button, its height value is the one declared in the @starting-style ruleset (1lh). After the transition-delay (which is .6s in the example), the height goes from 1lh to 0 in .3s, effectively hiding the popover.

Once again, this is only hiding the popover, not closing it properly. That’s the next challenge and we’ll need JavaScript for that level of interaction.

Closing the popover with JavaScript

We can start by setting a variable that selects the popover:

const POPOVER = document.querySelector('[popover]');

Next, we can establish a ResizeObserver that monitors the popover’s size:

const POPOVER = document.querySelector('[popover]'); const OBSERVER = new ResizeObserver((entries) => { if(entries[0].contentBoxSize[0].blockSize == 0) OBSERVER.unobserve((POPOVER.hidePopover(), POPOVER)); });

And we can fire that off starting when the button to show the popover is clicked:

const POPOVER = document.querySelector('[popover]'); const OBSERVER = new ResizeObserver((entries) => { if(entries[0].contentBoxSize[0].blockSize == 0) OBSERVER.unobserve((POPOVER.hidePopover(), POPOVER)); }); document.querySelector('button').onclick = () => OBSERVER.observe(POPOVER);

The observer will know when the popover’s CSS height reaches zero at the end of the transition, and, at that point, the popover is closed with hidePopover(). From there, the observer is stopped with unobserve().

In our example, height and ResizeObserver are used to auto-close the notification. You can try any other CSS property and JavaScript observer combination that might work with your preference. Learning about ResizeObserver and MutationObserver can help you find some options.

Setting an HTML fallback

When JavaScript is disabled in the browser, if the popover type is set to any of the light-dismissible types, it acts as a fallback. Keep the popover visible by overriding the style rules that hide it. The user can dismiss it by clicking or tapping anywhere outside the element.

If the popover needs to be light-dismissible only when JavaScript is disabled, then include that popover inside a <noscript> element before the manual popover. It’s the same process as before, where you override CSS styles as needed.

<noscript> <div popover="auto" id="pop">Bookmarked!</div> </noscript> <div popover="manual" id="pop">Bookmarked!</div> <!-- goes where <head> element's descendants go --> <noscript> <style> [popover] { transition: none; height: 1lh; } </style> </noscript> When to use this method?

Another way to implement all of this would be to use setTimeout() to create a delay before closing the popover in JavaScript when the button is clicked, then adding a class to the popover element to trigger the transition effect. That way, no observer is needed.

With the method covered in this post, the delay can be set and triggered in CSS itself, thanks to @starting-style and transition-delay — no extra class required! If you prefer to implement the delay through CSS itself, then this method works best. The JavaScript will catch up to the change CSS makes at the time CSS defines, not the other way around.

Creating an Auto-Closing Notification With an HTML Popover originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

As an increasing number of AI applications evolve to agents doing work for people, agent management becomes a critical part of these product's design. How can people start, steer, and stop multiple agents (and subagents) and stay on top of their results? Here's several approaches we've been building and testing.

Whenever a new technology emerges, user interfaces go through a balancing act between making the new technology approachable through common patterns and embodying what makes it unique. Make things too different and risk not having an onramp that brings people on board smoothly. Make things too familiar and risk limiting the potential of new capabilities within old models and interactions.

"Copy, extend, and finally, discovery of a new form. It takes a while to shed old paradigms." - Scott Jenson

As an example, Apple's VisionOS interface notably made use of many desktop and mobile interaction patterns to smooth the transition to spatial computing. But at the same time, they didn't take full advantage of spatial computing's opportunities by boxing limitless 3D interactions within the windows, icons, and menus, and pointers (WIMP) familiar to desktop interfaces.

Hence, the balancing act.

This context helps frame the way we've approached designing agent management interfaces. Are there high level user interface patterns that are both familiar enough for people to intuit how they work and flexible enough to enable effective AI agent management at a high level? In an agent-centric AI application like Augment Code for software development or Bench for office productivity, people need to be able to:

• Start new agents through a combination of instructions and context (files, connections, etc.)
• Schedule agents to run at certain times or under certain conditions.
• Scrutinize the work of agents to asses whether or not they're making the right kind of progress.
• Steer agents when they go off course, require clarification, or uncover something that suggests they should take a different path.
• Stop agents when they've either done enough or are no longer being effective.
• See, share, and save the results or processes of agents.

To help people adapt to agent management, we explored how interface patterns like kanban boards, dashboards, inboxes, tasks lists and calendars could fulfill many of these requirements by presenting the state of multiple agents and allowing people to access specific agents when they need to take further action.

Kanban Board

Kanban boards visualize work as cards moving through distinct stages, typically arranged in columns from left to right to represent progress through a workflow. They could be used to organize agents as they transition between scheduled, running, complete, and reviewed states. Or within workflows specific to domains like sales or engineering.

This pattern seems like a straightforward way to give people a sense of the state of multiple agents. But in kanban boards, people also expect to be able to move items between cards. How that would affect agents? Would they begin a new task defined by the card? Would that create a new agent or re-route an existing one?

Dashboard

Dashboards pull together multiple data sources into a unified monitoring interface through different visualizations like charts, graphs, and metrics. Unlike a kanban board, there's no workflow implied by the arrangement of the elements in a dashboard so you can pretty much represent agents anywhere and any way you like.

While that seems appealing, especially to those yearning for a "mission control" style interface to manage agents, it can quickly become problematic. When agents can be represented in different ways in different parts of a UI, it's hard to grasp both the big picture and details of what's happening.

Inbox

The inbox pattern organizes items in a chronological stream that requires user action to process. Items are listed from newest to oldest with visual cues like unread counts so people can quickly assess and act on items without losing context. Most of us do so every day in our messaging and email apps so applying the same model to agents seems natural.

But if you get too much email or too many texts, your inbox can get away from you. So it's not an ideal pattern for applications with a high volume of agents to manage nor for those that require coordination of multiple, potentially inter-dependent agents.

For what it's worth, this where we iterated to (for now) in Bench. So if you'd like to try this pattern out, fire off a few agents there.

Task List

Task lists present items as discrete, actionable units with clear completion states (usually a checkbox). Their vertical stack format lets people focus on specific tasks while still seeing the bigger picture. Task lists can be highly structured or pretty ad hoc lists of random to-dos.

Indented lists of subtasks can also display parallel agent processes and show the inter-dependencies of agents but perhaps at the expense of simplicity. In a single linear list, like an Inbox, its much easier to see what's happening than in a hierarchical task list where some subtasks may be collapsed but relevant.

Calendar

Calendar interfaces use a grid structure that maps to our understanding of time, with consistent rows and columns representing dates and times. This allows people to make use of both temporal memory and spatial memory to locate and contextualize items. Calendars also typically provide high level (month) and detailed (day) views of what's happening.

When it comes to scheduling agents, a calendar makes a lot of sense: just add it the same way you'd add a meeting. It's also helpful for contextually grouping the work of agents with actual meetings. "These tasks were all part of this project's brainstorm meeting." "I ran that task right after our one-on-one meeting." Representing the work of agents on a calendar can be tricky, though, as agents can run for minutes or many hours. And where should event-triggered agents should up on a calendar?

Coming back to Scott Jenson's quote at the start of this article, it takes a while to discover new paradigms and discover new forms. So it's quite likely as these interface patterns are adapted to agent management use cases, they'll evolve further and not end up looking much like their current selves. As David Hoang recently suggested, maybe agent management interfaces should learn from patterns found in Real-Time Strategy (RTS) games instead? Interesting...

If you’re following along, this is the third post in a series about the new CSS shape() function. We’ve learned how to draw lines and arcs and, in this third part, I will introduce the curve command — the missing command you need to know to have full control over the shape() function. In reality, there are more commands, but you will rarely need them and you can easily learn about them later by checking the documentation.

Better CSS Shapes Using shape()

1. Lines and Arcs
2. More on Arcs
3. Curves (you are here!)

The curve command

This command adds a Bézier curve between two points by specifying control points. We can either have one control point and create a Quadratic curve or two control points and create a Cubic curve.

Bézier, Quadratic, Cubic, control points? What?!

For many of you, that definition is simply unclear, or even useless! You can spend a few minutes reading about Bézier curves but is it really worth it? Probably not, unless your job is to create shapes all the day and you have a solid background in geometry.

We already have cubic-bezier() as an easing function for animations but, honestly, who really understands how it works? We either rely on a generator to get the code or we read a “boring” explanation that we forget in two minutes. (I have one right here by the way!)

Don’t worry, this article will not be boring as I will mostly focus on practical examples and more precisely the use case of rounding the corners of irregular shapes. Here is a figure to illustrate a few examples of Bézier curves.

The blue dots are the starting and ending points (let’s call them A and B) and the black dots are the control points. And notice how the curve is tangent to the dashed lines illustrated in red.

In this article, I will consider only one control point. The syntax will follow this pattern:

clip-path: shape( from Xa Ya, curve to Xb Yb with Xc Yc ); arc command vs. curve command

We already saw in Part 1 and Part 2 that the arc command is useful establishing rounded edges and corners, but it will not cover all the cases. That’s why you will need the curve command. The tricky part is to know when to use each one and the answer is “it depends.” There is no generic rule but my advice is to first see if it’s possible (and easy) using arc. If not, then you have to use curve.

For some shapes, we can have the same result using both commands and this is a good starting point for us to understand the curve command and compare it with arc.

Take the following example:

CodePen Embed Fallback

This is the code for the first shape:

.shape { clip-path: shape(from 0 0, arc to 100% 100% of 100% cw, line to 0 100%) }

And for the second one, we have this:

.shape { clip-path: shape(from 0 0, curve to 100% 100% with 100% 0, line to 0 100%) }

The arc command needs a radius (100% in this case), but the curve command needs a control point (which is 100% 0 in this example).

Now, if you look closely, you will notice that both results aren’t exactly the same. The first shape using the arc command is creating a quarter of a circle, whereas the shape using the curve command is slightly different. If you place both of them above each other, you can clearly see the difference.

CodePen Embed Fallback

This is interesting because it means we can round some corners using either an arc or a curve, but with slightly different results. Which one is better, you ask? I would say it depends on your visual preference and the shape you are creating.

In Part 1, we created rounded tabs using the arc command, but we can also create them with curve.

CodePen Embed Fallback

Can you spot the difference? It’s barely visible but it’s there.

Notice how I am using the by directive the same way I am doing with arc, but this time we have the control point, which is also relative. This part can be confusing, so pay close attention to this next bit.

Consider the following:

shape(from Xa Ya, curve by Xb Yb with Xc Yc)

It means that both (Xb,Yb) and (Xc,Yc) are relative coordinates calculated from the coordinate of the starting point. The equivalent of the above using a to directive is this:

shape(from Xa Ya, curve to (Xa + Xb) (Ya + Yb) with (Xa + Xc) (Yb + Yc))

We can change the reference of the control point by adding a from directive. We can either use start (the default value), end, or origin.

shape(from Xa Ya, curve by Xb Yb with Xc Yc from end)

The above means that the control point will now consider the ending point instead of the starting point. The result is similar to:

shape(from Xa Ya, curve to (Xa + Xb) (Ya + Yb) with (Xa + Xb + Xc) (Ya + Yb + Yc))

If you use origin, the reference will be the origin, hence the coordinate of the control point becomes absolute instead of relative.

The from directive may add some complexity to the code and the calculation, so don’t bother yourself with it. Simply know it exists in case you face it, but keep using the default value.

I think it’s time for your first homework! Similar to the rounded tab exercise, try to create the inverted radius shape we covered in the Part 1 using curve instead of arc. Here are both versions for you to reference, but try to do it without peeking first, if you can.

CodePen Embed Fallback Let’s draw more shapes!

Now that we have a good overview of the curve command, let’s consider more complex shapes where arc won’t help us round the corners and the only solution is to draw curves instead. Considering that each shape is unique, so I will focus on the technique rather than the code itself.

Slanted edge

Let’s start with a rectangular shape with a slanted edge.

Getting the shape on the left is quite simple, but the shape on the right is a bit tricky. We can round two corners with a simple border-radius, but for the slanted edge, we will use shape() and two curve commands.

The first step is to write the code of the shape without rounded corners (the left one) which is pretty straightforward since we’re only working with the line command:

.shape { --s: 90px; /* slant size */ clip-path: shape(from 0 0, line to calc(100% - var(--s)) 0, line to 100% 100%, line to 0 100% ); }

Then we take each corner and try to round it by modifying the code. Here is a figure to illustrate the technique I am going to use for each corner.

We define a distance, R, that controls the radius. From each side of the corner point, I move by that distance to create two new points, which are illustrated above in red. Then, I draw my curve using the new points as starting and ending points. The corner point will be the control point.

The code becomes:

.shape { --s: 90px; /* slant size */ clip-path: shape(from 0 0, Line to Xa Ya, curve to Xb Yb with calc(100% - var(--s)) 0, line to 100% 100%, line to 0 100% ); }

Notice how the curve is using the coordinates of the corner point in the with directive, and we have two new points, A and B.

Until now, the technique is not that complex. For each corner point, you replace the line command with line + curve commands where the curve command reuses the old point in its with directive.

If we apply the same logic to the other corner, we get the following:

.shape { --s: 90px; /* slant size */ clip-path: shape(from 0 0, line to Xa Ya, curve to Xb Yb with calc(100% - var(--s)) 0, line to Xc Yc, curve to Xd Yd with 100% 100%, line to 0 100% ); }

Now we need to calculate the coordinates of the new points. And here comes the tricky part because it’s not always simple and it may require some complex calculation. Even if I detail this case, the logic won’t be the same for the other shapes we’re making, so I will skip the math part and give you the final code:

.box { --h: 200px; /* element height */ --s: 90px; /* slant size */ --r: 20px; /* radius */ height: var(--h); border-radius: var(--r) 0 0 var(--r); --_a: atan2(var(--s), var(--h)); clip-path: shape(from 0 0, line to calc(100% - var(--s) - var(--r)) 0, curve by calc(var(--r) * (1 + sin(var(--_a)))) calc(var(--r) * cos(var(--_a))) with var(--r) 0, line to calc(100% - var(--r) * sin(var(--_a))) calc(100% - var(--r) * cos(var(--_a))), curve to calc(100% - var(--r)) 100% with 100% 100%, line to 0 100% ); }

I know the code looks a bit scary, but the good news is that the code is also really easy to control using CSS variables. So, even if the math is not easy to grasp, you don’t have to deal with it. It should be noted that I need to know the height to be able to calculate the coordinates which means the solution isn’t perfect because the height is a fixed value.

CodePen Embed Fallback Arrow-shaped box

Here’s a similar shape, but this time we have three corners to round using the curve command.

CodePen Embed Fallback

The final code is still complex but I followed the same steps. I started with this:

.shape { --s: 90px; clip-path: shape(from 0 0, /* corner #1 */ line to calc(100% - var(--s)) 0, /* corner #2 */ line to 100% 50%, /* corner #3 */ line to calc(100% - var(--s)) 100%, line to 0 100% ); }

Then, I modified it into this:

.shape { --s: 90px; clip-path: shape(from 0 0, /* corner #1 */ line to Xa Ya curve to Xb Yb with calc(100% - var(--s)) 0, /* corner #2 */ line to Xa Ya curve to Xb Yb with 100% 50%, /* corner #3 */ line to Xa Yb curve to Xb Yb with calc(100% - var(--s)) 100%, line to 0 100% ); }

Lastly, I use a pen and paper to do all the calculations.

You might think this technique is useless if you are not good with math and geometry, right? Not really, because you can still grab the code and use it easily since it’s optimized using CSS variables. Plus, you aren’t obligated to be super accurate and precise. You can rely on the above technique and use trial and error to approximate the coordinates. It will probably take you less time than doing all the math.

Rounded polygons

I know you are waiting for this, right? Thanks to the new shape() and the curve command, we can now have rounded polygon shapes!

Here is my implementation using Sass where you can control the radius, number of sides and the rotation of the shape:

CodePen Embed Fallback

If we omit the complex geometry part, the loop is quite simple as it relies on the same technique with a line + curve per corner.

$n: 9; /* number of sides*/ $r: .2; /* control the radius [0 1] */ $a: 15deg; /* control the rotation */ .poly { aspect-ratio: 1; $m: (); @for $i from 0 through ($n - 1) { $m: append($m, line to Xai Yai, comma); $m: append($m, curve to Xbi Ybi with Xci Yci, comma); } clip-path: shape(#{$m}); }

Here is another implementation where I define the variables in CSS instead of Sass:

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Having the variables in CSS is pretty handy especially if you want to have some animations. Here is an example of a cool hover effect applied to hexagon shapes:

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I have also updated my online generator to add the radius parameter. If you are not familiar with Sass, you can easily copy the CSS code from there. You will also find the border-only and cut-out versions!

Conclusion

Are we done with the curve command? Probably not, but we have a good overview of its potential and all the complex shapes we can build with it. As for the code, I know that we have reached a level that is not easy for everyone. I could have extended the explanation by explicitly breaking down the math, but then this article would be overly complex and make it seem like using shape() is harder than it is.

This said, most of the shapes I code are available within my online collection that I constantly update and optimize so you can easily grab the code of any shape!

If you want a good follow-up to this article, I wrote an article for Frontend Masters where you can create blob shapes using the curve command.

Better CSS Shapes Using shape()

1. Lines and Arcs
2. More on Arcs
3. Curves (you are here!)

Better CSS Shapes Using shape() — Part 3: Curves originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

In many countries, web accessibility is a human right and the law, and there can be heavy fines for non-compliance. Naturally, this means that text and icons and such must have optimal color contrast in accordance with the benchmarks set by the Web Content Accessibility Guidelines (WCAG). Now, there are quite a few color contrast checkers out there (Figma even has one built-in now), but the upcoming contrast-color() function doesn’t check color contrast, it outright resolves to either black or white (whichever one contrasts the most with your chosen color).

Right off the bat, you should know that we’ve sorta looked at this feature before. Back then, however, it was called color-contrast() instead of contrast-color() and had a much more convoluted way of going about things. It was only released in Safari Technology Preview 122 back in 2021, and that’s still the case at the time I’m writing this (now at version 220).

You’d use it like this:

button { --background-color: darkblue; background-color: var(--background-color); color: contrast-color(var(--background-color)); } CodePen Embed Fallback

Here, contrast-color() has determined that white contrasts with darkblue better than black does, which is why contrast-color() resolves to white. Pretty simple, really, but there are a few shortcomings, which includes a lack of browser support (again, it’s only in Safari Technology Preview at the moment).

We can use contrast-color() conditionally, though:

@supports (color: contrast-color(red)) { /* contrast-color() supported */ } @supports not (color: contrast-color(red)) { /* contrast-color() not supported */ } The shortcomings of contrast-color()

First, let me just say that improvements are already being considered, so here I’ll explain the shortcomings as well as any improvements that I’ve heard about.

Undoubtedly, the number one shortcoming is that contrast-color() only resolves to either black or white. If you don’t want black or white, well… that sucks. However, the draft spec itself alludes to more control over the resolved color in the future.

But there’s one other thing that’s surprisingly easy to overlook. What happens when neither black nor white is actually accessible against the chosen color? That’s right, it’s possible for contrast-color() to just… not provide a contrasting color. Ideally, I think we’d want contrast-color() to resolve to the closest accessible variant of a preferred color. Until then, contrast-color() isn’t really usable.

Another shortcoming of contrast-color() is that it only accepts arguments of the <color> data type, so it’s just not going to work with images or anything like that. I did, however, manage to make it “work” with a gradient (basically, two instances of contrast-color() for two color stops/one linear gradient):

CodePen Embed Fallback <button> <span>A button</span> </button> button { background: linear-gradient(to right, red, blue); span { background: linear-gradient(to right, contrast-color(red), contrast-color(blue)); color: transparent; background-clip: text; } }

The reason this looks so horrid is that, as mentioned before, contrast-color() only resolves to black or white, so in the middle of the gradient we essentially have 50% grey on purple. This problem would also get solved by contrast-color() resolving to a wider spectrum of colors.

But what about the font size? As you might know already, the criteria for color contrast depends on the font size, so how does that work? Well, at the moment it doesn’t, but I think it’s safe to assume that it’ll eventually take the font-size into account when determining the resolved color. Which brings us to APCA.

APCA (Accessible Perceptual Contrast Algorithm) is a new algorithm for measuring color contrast reliably. Andrew Somers, creator of APCA, conducted studies (alongside many other independent studies) and learned that 23% of WCAG 2 “Fails” are actually accessible. In addition, an insane 47% of “Passes” are inaccessible.

Not only should APCA do a better job, but the APCA Readability Criterion (ARC) is far more nuanced, taking into account a much wider spectrum of font sizes and weights (hooray for me, as I’m very partial to 600 as a standard font weight). While the criterion is expectedly complex and unnecessarily confusing, the APCA Contrast Calculator does a decent-enough job of explaining how it all works visually, for now.

contrast-color() doesn’t use APCA, but the draft spec does allude to offering more algorithms in the future. This wording is odd as it suggests that we’ll be able to choose between the APCA and WCAG algorithms. Then again, we have to remember that the laws of some countries will require WCAG 2 compliance while others require WCAG 3 compliance (when it becomes a standard).

That’s right, we’re a long way off of APCA becoming a part of WCAG 3, let alone contrast-color(). In fact, it might not even be a part of it initially (or at all), and there are many more hurdles after that, but hopefully this sheds some light on the whole thing. For now, contrast-color() is using WCAG 2 only.

Using contrast-color()

Here’s a simple example (the same one from earlier) of a darkblue-colored button with accessibly-colored text chosen by contrast-color(). I’ve put this darkblue color into a CSS variable so that we can define it once but reference it as many times as is necessary (which is just twice for now).

button { --background-color: darkblue; background-color: var(--background-color); /* Resolves to white */ color: contrast-color(var(--background-color)); }

And the same thing but with lightblue:

button { --background-color: lightblue; background-color: var(--background-color); /* Resolves to black */ color: contrast-color(var(--background-color)); }

First of all, we can absolutely switch this up and use contrast-color() on the background-color property instead (or in-place of any <color>, in fact, like on a border):

button { --color: darkblue; color: var(--color); /* Resolves to white */ background-color: contrast-color(var(--color)); }

Any valid <color> will work (named, HEX, RGB, HSL, HWB, etc.):

button { /* HSL this time */ --background-color: hsl(0 0% 0%); background-color: var(--background-color); /* Resolves to white */ color: contrast-color(var(--background-color)); }

Need to change the base color on the fly (e.g., on hover)? Easy:

button { --background-color: hsl(0 0% 0%); background-color: var(--background-color); /* Starts off white, becomes black on hover */ color: contrast-color(var(--background-color)); &:hover { /* 50% lighter */ --background-color: hsl(0 0% 50%); } } CodePen Embed Fallback

Similarly, we could use contrast-color() with the light-dark() function to ensure accessible color contrast across light and dark modes:

:root { /* Dark mode if checked */ &:has(input[type="checkbox"]:checked) { color-scheme: dark; } /* Light mode if not checked */ &:not(:has(input[type="checkbox"]:checked)) { color-scheme: light; } body { /* Different background for each mode */ background: light-dark(hsl(0 0% 50%), hsl(0 0% 0%)); /* Different contrasted color for each mode */ color: light-dark(contrast-color(hsl(0 0% 50%)), contrast-color(hsl(0 0% 0%)); } } CodePen Embed Fallback

The interesting thing about APCA is that it accounts for the discrepancies between light mode and dark mode contrast, whereas the current WCAG algorithm often evaluates dark mode contrast inaccurately. This one nuance of many is why we need not only a new color contrast algorithm but also the contrast-color() CSS function to handle all of these nuances (font size, font weight, etc.) for us.

This doesn’t mean that contrast-color() has to ensure accessibility at the expense of our “designed” colors, though. Instead, we can use contrast-color() within the prefers-contrast: more media query only:

button { --background-color: hsl(270 100% 50%); background-color: var(--background-color); /* Almost white (WCAG AA: Fail) */ color: hsl(270 100% 90%); @media (prefers-contrast: more) { /* Resolves to white (WCAG AA: Pass) */ color: contrast-color(var(--background-color)); } }

Personally, I’m not keen on prefers-contrast: more as a progressive enhancement. Great color contrast benefits everyone, and besides, we can’t be sure that those who need more contrast are actually set up for it. Perhaps they’re using a brand new computer, or they just don’t know how to customize accessibility settings.

Closing thoughts

So, contrast-color() obviously isn’t useful in its current form as it only resolves to black or white, which might not be accessible. However, if it were improved to resolve to a wider spectrum of colors, that’d be awesome. Even better, if it were to upgrade colors to a certain standard (e.g., WCAG AA) if they don’t already meet it, but let them be if they do. Sort of like a failsafe approach? This means that web browsers would have to take the font size, font weight, element, and so on into account.

To throw another option out there, there’s also the approach that Windows takes for its High Contrast Mode. This mode triggers web browsers to overwrite colors using the forced-colors: active media query, which we can also use to make further customizations. However, this effect is quite extreme (even though we can opt out of it using the forced-colors-adjust CSS property and use our own colors instead) and macOS’s version of the feature doesn’t extend to the web.

I think that forced colors is an incredible idea as long as users can set their contrast preferences when they set up their computer or browser (the browser would be more enforceable), and there are a wider range of contrast options. And then if you, as a designer or developer, don’t like the enforced colors, then you have the option to meet accessibility standards so that they don’t get enforced. In my opinion, this approach is the most user-friendly and the most developer-friendly (assuming that you care about accessibility). For complete flexibility, there could be a CSS property for opting out, or something. Just color contrast by default, but you can keep the colors you’ve chosen as long as they’re accessible.

What do you think? Is contrast-color() the right approach, or should the user agent bear some or all of the responsibility? Or perhaps you’re happy for color contrast to be considered manually?

Exploring the CSS contrast-color() Function… a Second Time originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

The State of CSS 2025 Survey dropped a few days ago, and besides waiting for the results, it’s exciting to see a lot of the new things shipped to CSS over the past year reflected in the questions. To be specific, the next survey covers the following features:

• calc-size()
• shape()
• Scroll-driven animations
• Container scroll-state queries
• CSS Carousels
• text-box-edge and text-box-trim
• field-sizing
• ::target-text
• @function
• display: contents
• Advanced attr()
• if()
• sibling-index() and sibling-count()

Again, a lot!

However, I think the most important questions (regarding CSS) are asked at the end of each section. I am talking about the “What are your top CSS pain points related to ______?” questions. These sections are optional, but help user agents and the CSS Working Group know what they should focus on next.

By nature of comments, those respondents with strong opinions are most likely to fill them in, skewing data towards issues that maybe the majority doesn’t have. So, even if you don’t have a hard-set view on a CSS pain point, I encourage you to fill them — even with your mild annoyances.

The State of CSS 2025 Survey is out! originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Like ’em or loath ’em, whether you’re showing an alert, a message, or a newsletter signup, dialogue boxes draw attention to a particular piece of content without sending someone to a different page. In the past, dialogues relied on a mix of divisions, ARIA, and JavaScript. But the HTML dialog element has made them more accessible and style-able in countless ways.

So, how can you take dialogue box design beyond the generic look of frameworks and templates? How can you style them to reflect a brand’s visual identity and help to tell its stories? Here’s how I do it in CSS using ::backdrop, backdrop-filter, and animations.

Design by Andy Clarke, Stuff & Nonsense. Mike Worth’s website will launch in June 2025, but you can see examples from this article on CodePen.

I mentioned before that Emmy-award-winning game composer Mike Worth hired me to create a highly graphical design. Mike loves ’90s animation, and he challenged me to find ways to incorporate its retro style without making a pastiche. However, I also needed to achieve that retro feel while maintaining accessibility, performance, responsiveness, and semantics.

A brief overview of dialog and ::backdrop

Let’s run through a quick refresher.

Note: While I mostly refer to “dialogue boxes” throughout, the HTML element is spelt dialog.

dialog is an HTML element designed for implementing modal and non-modal dialogue boxes in products and website interfaces. It comes with built-in functionality, including closing a box using the keyboard Esc key, focus trapping to keep it inside the box, show and hide methods, and a ::backdrop pseudo-element for styling a box’s overlay.

The HTML markup is just what you might expect:

<dialog> <h2>Keep me informed</h2> <!-- ... --> <button>Close</button> </dialog>

This type of dialogue box is hidden by default, but adding the open attribute makes it visible when the page loads:

<dialog open> <h2>Keep me informed</h2> <!-- ... --> <button>Close</button> </dialog>

I can’t imagine too many applications for non-modals which are open by default, so ordinarily I need a button which opens a dialogue box:

<dialog> <!-- ... --> </dialog> <button>Keep me informed</button>

Plus a little bit of JavaScript, which opens the modal:

const dialog = document.querySelector("dialog"); const showButton = document.querySelector("dialog + button"); showButton.addEventListener("click", () => { dialog.showModal(); });

Closing a dialogue box also requires JavaScript:

const closeButton = document.querySelector("dialog button"); closeButton.addEventListener("click", () => { dialog.close(); });

Unless the box contains a form using method="dialog", which allows it to close automatically on submit without JavaScript:

<dialog> <form method="dialog"> <button>Submit</button> </form> </dialog>

The dialog element was developed to be accessible out of the box. It traps focus, supports the Esc key, and behaves like a proper modal. But to help screen readers announce dialogue boxes properly, you’ll want to add an aria-labelledby attribute. This tells assistive technology where to find the dialogue box’s title so it can be read aloud when the modal opens.

<dialog aria-labelledby="dialog-title"> <h2 id="dialog-title">Keep me informed</h2> <!-- ... --> </dialog>

Most tutorials I’ve seen include very little styling for dialog and ::backdrop, which might explain why so many dialogue boxes have little more than border radii and a box-shadow applied.

Out-of-the-box dialogue designs

I believe that every element in a design — no matter how small or infrequently seen — is an opportunity to present a brand and tell a story about its products or services. I know there are moments during someone’s journey through a design where paying special attention to design can make their experience more memorable.

Dialogue boxes are just one of those moments, and Mike Worth’s design offers plenty of opportunities to reflect his brand or connect directly to someone’s place in Mike’s story. That might be by styling a newsletter sign-up dialogue to match the scrolls in his news section.

Mike Worth concept design, designed by Andy Clarke, Stuff & Nonsense.

Or making the form modal on his error pages look like a comic-book speech balloon.

Mike Worth concept design, designed by Andy Clarke, Stuff & Nonsense. dialog in action

Mike’s drop-down navigation menu looks like an ancient stone tablet.

Mike Worth, designed by Andy Clarke, Stuff & Nonsense.

I wanted to extend this look to his dialogue boxes with a three-dimensional tablet and a jungle leaf-filled backdrop.

Mike Worth, designed by Andy Clarke, Stuff & Nonsense.

This dialog contains a newsletter sign-up form with an email input and a submit button:

<dialog> <h2>Keep me informed</h2> <form> <label for="email" data-visibility="hidden">Email address</label> <input type="email" id="email" required> <button>Submit</button> </form> <button>x</button> </dialog>

I started by applying dimensions to the dialog and adding the SVG stone tablet background image:

dialog { width: 420px; height: 480px; background-color: transparent; background-image: url("dialog.svg"); background-repeat: no-repeat; background-size: contain; }

Then, I added the leafy green background image to the dialogue box’s generated backdrop using the ::backdrop pseudo element selector:

dialog::backdrop { background-image: url("backdrop.svg"); background-size: cover; } Mike Worth, designed by Andy Clarke, Stuff & Nonsense.

I needed to make it clear to anyone filling in Mike’s form that their email address is in a valid format. So I combined :has and :valid CSS pseudo-class selectors to change the color of the submit button from grey to green:

dialog:has(input:valid) button { background-color: #7e8943; color: #fff; }

I also wanted this interaction to reflect Mike’s fun personality. So, I also changed the dialog background image and applied a rubberband animation to the box when someone inputs a valid email address:

dialog:has(input:valid) { background-image: url("dialog-valid.svg"); animation: rubberBand 0.82s cubic-bezier(0.36, 0.07, 0.19, 0.97) both; } @keyframes rubberBand { from { transform: scale3d(1, 1, 1); } 30% { transform: scale3d(1.25, 0.75, 1); } 40% { transform: scale3d(0.75, 1.25, 1); } 50% { transform: scale3d(1.15, 0.85, 1); } 65% { transform: scale3d(0.95, 1.05, 1); } 75% { transform: scale3d(1.05, 0.95, 1); } to { transform: scale3d(1, 1, 1); } }

Tip: Daniel Eden’s Animate.css library is a fabulous source of “Just-add-water CSS animations” like the rubberband I used for this dialogue box.

Changing how an element looks when it contains a valid input is a fabulous way to add interactions that are, at the same time, fun and valuable for the user.

Mike Worth, designed by Andy Clarke, Stuff & Nonsense.

That combination of :has and :valid selectors can even be extended to the ::backdrop pseudo-class, to change the backdrop’s background image:

dialog:has(input:valid)::backdrop { background-image: url("backdrop-valid.svg"); }

Try it for yourself:

CodePen Embed Fallback Conclusion

We often think of dialogue boxes as functional elements, as necessary interruptions, but nothing more. But when you treat them as opportunities for expression, even the smallest parts of a design can help shape a product or website’s personality.

The HTML dialog element, with its built-in behaviours and styling potential, opens up opportunities for branding and creative storytelling. There’s no reason a dialogue box can’t be as distinctive as the rest of your design.

Andy Clarke

Often referred to as one of the pioneers of web design, Andy Clarke has been instrumental in pushing the boundaries of web design and is known for his creative and visually stunning designs. His work has inspired countless designers to explore the full potential of product and website design.

Andy’s written several industry-leading books, including ‘Transcending CSS,’ ‘Hardboiled Web Design,’ and ‘Art Direction for the Web.’ He’s also worked with businesses of all sizes and industries to achieve their goals through design.

Visit Andy’s studio, Stuff & Nonsense, and check out his Contract Killer, the popular web design contract template trusted by thousands of web designers and developers.

Getting Creative With HTML Dialog originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

While chat interfaces to AI models aren't going away anytime soon, the increasing capabilities of AI agents are making the concept of chatting back and forth with an AI model to get things done feel archaic.

Let me first clarify that I don't mean open-ended text fields where people declare their intent are going away. As I wrote recently there will be even more broad input affordances in software whether for text, image, audio, video, or more. When I say chat AIs, I mean applications whose primary mode of getting things done is through a back and forth messaging conversation with an AI model: you type something, the model responds, you type something... and on it goes until you get the output you need.

Anyone that's interacted with an application like this knows that the AI model's responses quickly get lost in conversation threads and producing something from a set of chat replies can be painful. This kind of interface isn't optimal for tasks like authoring a document, writing code, or creating slides. To account for this some applications now include a canvas or artifact area where the output of the AI model's work can go.

In these layouts, the chat interface usually goes from being a single-pane layout to a split-pane layout. Roughly half the UI for input in the form of chat and half of it for output in the form of a canvas or artifact viewer. In these kinds of applications, we already begin to see the prominence of chat receding as people move between providing input and reviewing, editing, or acting on output.

In this model, however, the onus is still on the user to chat back and forth with a model until it produces their desired output in the artifact or canvas pane. Agents (AI models to make use of tools) change this dynamic. People state their objectives and the AI model(s) plans which tools to use and how to accomplish their task.

Instead of each step being a back and forth chat between a person and an AI model, the vast majority, if not all, of the steps are coordinated by the model(s) itself. This again reduces the role of chat. The model(s) takes care of the back and forth and in most cases simply lets people know when its done so they can review and make use of its output.

When agents can use multiple tools, call other agents and run in the background, a person's role moves to kicking things off, clarifying things when needed, and making use of the final output. There's a lot less chatting back and forth. As such, the prominence of the chat interface can recede even further. It's there if you want to check the steps an AI took to accomplish your task. But until then it's out of your way so you can focus on the output.

You can see this UI transition in the AI workspace, Bench. The first version was focused on back and forth instructions with models to get things done: a single-pane AI chat UI. Then a split-paned interface put more emphasis on the results of these instructions with half the screen devoted to an output pane. Today Bench runs and coordinates agents in the background. So the primary interaction is kicking off tasks and reviewing results when they're ready.

In this UI, the chat interface is not only reduced to less than a fourth of the screen but also collapsed by default hiding the model's back and forth conversations with itself unless people want to dig into it.

When working with AI models this way, the process of chatting back and forth to create things within in messaging UI feels dated. AI that takes your instructions, figures out how to get things done using tools, multiple models, changeable plans, and just tells you when it's finished feels a lot more like "the future". Of course I put future in quotes because at the rate AI moves these days the future will be here way sooner than any of us think. So... more UI changes to come!

The reading-flow and reading-order proposed CSS properties are designed to specify the source order of HTML elements in the DOM tree, or in simpler terms, how accessibility tools deduce the order of elements. You’d use them to make the focus order of focusable elements match the visual order, as outlined in the Web Content Accessibility Guidelines (WCAG 2.2).

To get a better idea, let’s just dive in!

(Oh, and make sure that you’re using Chrome 137 or higher.)

reading-flow

reading-flow determines the source order of HTML elements in a flex, grid, or block layout. Again, this is basically to help accessibility tools provide the correct focus order to users.

The default value is normal (so, reading-flow: normal). Other valid values include:

• flex-visual
• flex-flow
• grid-rows
• grid-columns
• grid-order
• source-order

Let’s start with the flex-visual value. Imagine a flex row with five links. Assuming that the reading direction is left-to-right (by the way, you can change the reading direction with the direction CSS property), that’d look something like this:

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Now, if we apply flex-direction: row-reverse, the links are displayed 5-4-3-2-1. The problem though is that the focus order still starts from 1 (tab through them!), which is visually wrong for somebody that reads left-to-right.

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But if we also apply reading-flow: flex-visual, the focus order also becomes 5-4-3-2-1, matching the visual order (which is an accessibility requirement!):

<div> <a>1</a> <a>2</a> <a>3</a> <a>4</a> <a>5</a> </div> div { display: flex; flex-direction: row-reverse; reading-flow: flex-visual; } CodePen Embed Fallback

To apply the default flex behavior, reading-flow: flex-flow is what you’re looking for. This is very akin to reading-flow: normal, except that the container remains a reading flow container, which is needed for reading-order (we’ll dive into this in a bit).

For now, let’s take a look at the grid-y values. In the grid below, the grid items are all jumbled up, and so the focus order is all over the place.

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We can fix this in two ways. One way is that reading-flow: grid-rows will, as you’d expect, establish a row-by-row focus order:

<div> <a>1</a> <a>2</a> <a>3</a> <a>4</a> <a>5</a> <a>6</a> <a>7</a> <a>8</a> <a>9</a> <a>10</a> <a>11</a> <a>12</a> </div> div { display: grid; grid-template-columns: repeat(4, 1fr); grid-auto-rows: 100px; reading-flow: grid-rows; a:nth-child(2) { grid-row: 2 / 4; grid-column: 3; } a:nth-child(5) { grid-row: 1 / 3; grid-column: 1 / 3; } } CodePen Embed Fallback

Or, reading-flow: grid-columns will establish a column-by-column focus order:

CodePen Embed Fallback

reading-flow: grid-order will give us the default grid behavior (i.e., the jumbled up version). This is also very akin to reading-flow: normal (except that, again, the container remains a reading flow container, which is needed for reading-order).

There’s also reading-flow: source-order, which is for flex, grid, and block containers. It basically turns containers into reading flow containers, enabling us to use reading-order. To be frank, unless I’m missing something, this appears to make the flex-flow and grid-order values redundant?

reading-order

reading-order sort of does the same thing as reading-flow. The difference is that reading-order is for specific flex or grid items, or even elements in a simple block container. It works the same way as the order property, although I suppose we could also compare it to tabindex.

Note: To use reading-order, the container must have the reading-flow property set to anything other than normal.

I’ll demonstrate both reading-order and order at the same time. In the example below, we have another flex container where each flex item has the order property set to a different random number, making the order of the flex items random. Now, we’ve already established that we can use reading-flow to determine focus order regardless of visual order, but in the example below we’re using reading-order instead (in the exact same way as order):

div { display: flex; reading-flow: source-order; /* Anything but normal */ /* Features at the end because of the higher values */ a:nth-child(1) { /* Visual order */ order: 567; /* Focus order */ reading-order: 567; } a:nth-child(2) { order: 456; reading-order: 456; } a:nth-child(3) { order: 345; reading-order: 345; } a:nth-child(4) { order: 234; reading-order: 234; } /* Features at the beginning because of the lower values */ a:nth-child(5) { order: -123; reading-order: -123; } } CodePen Embed Fallback

Yes, those are some rather odd numbers. I’ve done this to illustrate how the numbers don’t represent the position (e.g., order: 3 or reading-order: 3 doesn’t make it third in the order). Instead, elements with lower numbers are more towards the beginning of the order and elements with higher numbers are more towards the end. The default value is 0. Elements with the same value will be ordered by source order.

In practical terms? Consider the following example:

div { display: flex; reading-flow: source-order; a:nth-child(1) { order: 1; reading-order: 1; } a:nth-child(5) { order: -1; reading-order: -1; } } CodePen Embed Fallback

Of the five flex items, the first one is the one with order: -1 because it has the lowest order value. The last one is the one with order: 1 because it has the highest order value. The ones with no declaration default to having order: 0 and are thus ordered in source order, but otherwise fit in-between the order: -1 and order: 1 flex items. And it’s the same concept for reading-order, which in the example above mirrors order.

However, when reversing the direction of flex items, keep in mind that order and reading-order work a little differently. For example, reading-order: -1 would, as expected, and pull a flex item to the beginning of the focus order. Meanwhile, order: -1 would pull it to the end of the visual order because the visual order is reversed (so we’d need to use order: 1 instead, even if that doesn’t seem right!):

div { display: flex; flex-direction: row-reverse; reading-flow: source-order; a:nth-child(5) { /* Because of row-reverse, this actually makes it first */ order: 1; /* However, this behavior doesn’t apply to reading-order */ reading-order: -1; } } CodePen Embed Fallback

reading-order overrides reading-flow. If we, for example, apply reading-flow: flex-visual, reading-flow: grid-rows, or reading-flow: grid-columns (basically, any declaration that does in fact change the reading flow), reading-order overrides it. We could say that reading-order is applied after reading-flow.

What if I don’t want to use flexbox or grid layout?

Well, that obviously rules out all of the flex-y and grid-y reading-flow values; however, you can still set reading-flow: source-order on a block element and then manipulate the focus order with reading-order (as we did above).

How does this relate to the tabindex HTML attribute?

They’re not equivalent. Negative tabindex values make targets unfocusable and values other than 0 and -1 aren’t recommended, whereas a reading-order declaration can use any number as it’s only contextual to the reading flow container that contains it.

For the sake of being complete though, I did test reading-order and tabindex together and reading-order appeared to override tabindex.

Going forward, I’d only use tabindex (specifically, tabindex="-1") to prevent certain targets from being focusable (the disabled attribute will be more appropriate for some targets though), and then reading-order for everything else.

Closing thoughts

Being able to define reading order is useful, or at least it means that the order property can finally be used as intended. Up until now (or rather when all web browsers support reading-flow and reading-order, because they only work in Chrome 137+ at the moment), order hasn’t been useful because we haven’t been able to make the focus order match the visual order.

What We Know (So Far) About CSS Reading Order originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

The last two weeks featured a flurry of new AI model announcements. Keeping up with these changes can be hard without some kind of personal benchmark. For me, that's been my personal AI feature, Ask LukeW, which allows me to both quickly try and put new models into production.

To start... what were all these announcements? On May 14th, OpenAI released three new models in their GPT-4.1 series. On May 20th at I/O, Google updated Gemini 2.5 Pro. On May 22nd, Anthropic launched Claude Opus 4 and Claude Sonnet 4. So clearly high-end model releases aren't slowing down anytime soon.

Many AI-powered applications develop and use their own benchmarks to evaluate new models when they become available. But there's still nothing quite like trying an AI model yourself in a domain or problem space you know very well to gauge its strengths and weaknesses.

To do this more easily, I added the ability to quickly test new models on the Ask LukeW feature of this site. Because Ask LukeW works with the thousands of articles I've written and hundreds of presentations I've given, it's a really effective way for me to see what's changed. Essentially, I know what good looks like because I know what the answers should be.

The Ask LukeW system retrieves as much relevant content as possible before asking a large language model (LLM) to generate an answer to someone's question (as seen in the system diagram). As a result, the LLM can have lots of content to make sense of when things get to the generation part of the pipeline.

Previously this resulted in a lot of "kitchen sink" style bullet point answers as frontier models mostly leaned toward including as much information as possible. These kinds of replies ended up using lots of words without clearly getting to the point. After some testing, I found Anthropic's Claude Opus 4 is much better at putting together responses that feel like they understood the essence of a question. You can see the difference in the before and after examples in this article. The responses to questions with lots of content to synthesize feel more coherent and concise.

It's worth noting I'm only using Opus 4 is for the generation part of the Ask LukeW pipeline which uses AI models to not only generate but also transform, clean, embed, retrieve, and rank content. So there's many other parts of the pipeline where testing new models matters but in the final generation step at the end, Opus 4 wins. For now...

Creating CSS Shapes is a classic and one of my favorite exercise. Indeed, I have one of the biggest collections of CSS Shapes from where you can easily copy the code of any shape. I also wrote an extensive guide on how to create them: The Modern Guide For Making CSS Shapes.

Even if I have detailed most of the modern techniques and tricks, CSS keeps evolving, and new stuff always emerges to simplify our developer life. Recently, clip-path was upgraded to have a new shape() value. A real game changer!

Better CSS Shapes Using shape()

1. Lines and Arcs (you are here!)
2. More on Arcs
3. Curves

Before we jump in, it’s worth calling out that the shape() function is currently only supported in Chrome 137+ and Safari 18.4+ as I’m writing this in May 2025.

What is shape()?

Let me quote the description from the official specification:

While the path() function allows reuse of the SVG path syntax to define more arbitrary shapes than allowed by more specialized shape functions, it requires writing a path as a single string (which is not compatible with, for example, building a path piecemeal with var()), and inherits a number of limitations from SVG, such as implicitly only allowing the px unit.

The shape() function uses a set of commands roughly equivalent to the ones used by path(), but does so with more standard CSS syntax, and allows the full range of CSS functionality, such as additional units and math functions.

In other words, we have the SVG features in the CSS side that we can combine with existing features such as var(), calc(), different units, etc. SVG is already good at drawing complex shapes, so imagine what is possible with something more powerful.

If you keep reading the spec, you will find:

In that sense, shape() is a superset of path(). A path() can be easily converted to a shape(), but to convert a shape() back to a path() or to SVG requires information about the CSS environment.

And guess what? I already created an online converter from SVG to CSS. Save this tool because it will be very handy. If you are already good at creating SVG shapes or you have existing codes, no need to reinvent the wheel. You paste your code in the generator, and you get the CSS code that you can easily tweak later.

Let’s try with the CSS-Tricks logo. Here is the SVG I picked from the website:

<svg width="35px" height="35px" viewBox="0 0 362.62 388.52" > <path d="M156.58,239l-88.3,64.75c-10.59,7.06-18.84,11.77-29.43,11.77-21.19,0-38.85-18.84-38.85-40C0,257.83,14.13,244.88,27.08,239l103.6-44.74L27.08,148.34C13,142.46,0,129.51,0,111.85,0,90.66,18.84,73,40,73c10.6,0,17.66,3.53,28.25,11.77l88.3,64.75L144.81,44.74C141.28,20,157.76,0,181.31,0s40,18.84,36.5,43.56L206,149.52l88.3-64.75C304.93,76.53,313.17,73,323.77,73a39.2,39.2,0,0,1,38.85,38.85c0,18.84-12.95,30.61-27.08,36.5L231.93,194.26,335.54,239c14.13,5.88,27.08,18.83,27.08,37.67,0,21.19-18.84,38.85-40,38.85-9.42,0-17.66-4.71-28.26-11.77L206,239l11.77,104.78c3.53,24.72-12.95,44.74-36.5,44.74s-40-18.84-36.5-43.56Z"></path> </svg>

You take the value inside the d attribute, paste it in the converter, and boom! You have the following CSS:

.shape { aspect-ratio: 0.933; clip-path: shape(from 43.18% 61.52%,line by -24.35% 16.67%,curve by -8.12% 3.03% with -2.92% 1.82%/-5.2% 3.03%,curve by -10.71% -10.3% with -5.84% 0%/-10.71% -4.85%,curve to 7.47% 61.52% with 0% 66.36%/3.9% 63.03%,line by 28.57% -11.52%,line to 7.47% 38.18%,curve to 0% 28.79% with 3.59% 36.67%/0% 33.33%,curve to 11.03% 18.79% with 0% 23.33%/5.2% 18.79%,curve by 7.79% 3.03% with 2.92% 0%/4.87% 0.91%,line by 24.35% 16.67%,line to 39.93% 11.52%,curve to 50% 0% with 38.96% 5.15%/43.51% 0%,smooth by 10.07% 11.21% with 11.03% 4.85%,line to 56.81% 38.48%,line by 24.35% -16.67%,curve to 89.29% 18.79% with 84.09% 19.7%/86.36% 18.79%,arc by 10.71% 10% of 10.81% 10.09% small cw,curve by -7.47% 9.39% with 0% 4.85%/-3.57% 7.88%,line to 63.96% 50%,line to 92.53% 61.52%,curve by 7.47% 9.7% with 3.9% 1.51%/7.47% 4.85%,curve by -11.03% 10% with 0% 5.45%/-5.2% 10%,curve by -7.79% -3.03% with -2.6% 0%/-4.87% -1.21%,line to 56.81% 61.52%,line by 3.25% 26.97%,curve by -10.07% 11.52% with 0.97% 6.36%/-3.57% 11.52%,smooth by -10.07% -11.21% with -11.03% -4.85%,close); }

Note that you don’t need to provide any viewBox data. The converter will automatically find the smallest rectangle for the shape and will calculate the coordinates of the points accordingly. No more viewBox headaches and no need to fight with overflow or extra spacing!

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Here is another example where I am applying the shape to an image element. I am keeping the original SVG so you can compare both shapes.

CodePen Embed Fallback When to use shape()

I would be tempted to say “all the time” but in reality, not. In my guide, I distinguish between two types of shapes: The ones with only straight lines and the ones with curves. Each type can either have repetition or not. In the end, we have four categories of shapes.

If we don’t have curves and we don’t have repetition (the easiest case), then clip-path: polygon() should do the job. If we have a repetition (with or without curves), then mask is the way to go. With mask, we can rely on gradients that can have a specific size and repeat, but with clip-path we don’t have such options.

If you have curves and don’t have a repetition, the new shape() is the best option. Previously, we had to rely on mask since clip-path is very limited, but that’s no longer the case. Of course, these are not universal rules, but my own way to identify which option is the most suitable. At the end of the day, it’s always a case-by-case basis as we may have other things to consider, such as the complexity of the code, the flexibility of the method, browser support, etc.

Let’s draw some shapes!

Enough talking, let’s move to the interesting part: drawing shapes. I will not write a tutorial to explain the “complex” syntax of shape(). It will be boring and not interesting. Instead, we will draw some common shapes and learn by practice!

Rectangle

Take the following polygon:

clip-path: polygon( 0 0, 100% 0, 100% 100%, 0 100% );

Technically, this will do nothing since it will draw a rectangle that already follows the element shape which is a rectangle, but it’s still the perfect starting point for us.

Now, let’s write it using shape().

clip-path: shape( from 0 0, line to 100% 0, line to 100% 100%, line to 0 100% );

The code should be self-explanatory and we already have two commands. The from command is always the first command and is used only once. It simply specifies the starting point. Then we have the line command that draws a line to the next point. Nothing complex so far.

We can still write it differently like below:

clip-path: shape( from 0 0, hline to 100%, vline to 100%, hline to 0 );

Between the points 0 0 and 100% 0, only the first value is changing which means we are drawing a horizontal line from 0 0 to 100% 0, hence the use of hline to 100% where you only need to specify the horizontal offset. It’s the same logic using vline where we draw a vertical line between 100% 0 and 100% 100%.

I won’t advise you to draw your shape using hline and vline because they can be tricky and are a bit difficult to read. Always start by using line and then if you want to optimize your code you can replace them with hline or vline when applicable.

We have our first shape and we know the commands to draw straight lines:

CodePen Embed Fallback Circular Cut-Out

Now, let’s try to add a circular cut-out at the top of our shape:

For this, we are going to rely on the arc command, so let’s understand how it works.

If we have two points, A and B, there are exactly two circles with a given radius that intersect with both points like shown in the figure. The intersection gives us four possible arcs we can draw between points A and B. Each arc is defined by a size and a direction.

There is also the particular case where the radius is equal to half the distance between A and B. In this case, only two arcs can be drawn and the direction will decide which one.

The syntax will look like this:

clip-path: shape( from Xa Ya, arc to Xb Yb of R [large or small] [cw or ccw] );

Let’s add this to our previous shape. No need to think about the values. Instead, let’s use random ones and see what happens:

clip-path: shape( from 0 0, arc to 40% 0 of 50px, line to 100% 0, line to 100% 100%, line to 0 100% ); CodePen Embed Fallback

Not bad, we can already see the arc between 0 0 and 40% 0. Notice how I didn’t define the size and direction of the arc. By default, the browser will use small and ccw.

Let’s explicitly define the size and direction to see the four different cases:

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Hmm, it’s working for the first two blocks but not the other ones. Quite strange, right?

Actually, everything is working fine. The arcs are drawn outside the element area so nothing is visible. If you add some box-shadow, you can see them:

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Arcs can be tricky due to the size and direction thing, so get ready to be confused. If that happens, remember that you have four different cases, and trying all of them will help you find which one you need.

Now let’s try to be accurate and draw half a circle with a specific radius placed at the center:

We can define the radius as a variable and use what we have learned so far:

.shape { --r: 50px; clip-path: shape( from 0 0, line to calc(50% - var(--r)) 0, arc to calc(50% + var(--r)) 0 of var(--r), line to 100% 0, line to 100% 100%, line to 0 100% ); } CodePen Embed Fallback

It’s working fine, but the code can still be optimized. We can replace all the line commands with hline and vline like below:

.shape { --r: 50px; clip-path: shape(from 0 0, hline to calc(50% - var(--r)), arc to calc(50% + var(--r)) 0 of var(--r), hline to 100%, vline to 100%, hline to 0 ); }

We can also replace the radius with 1%:

.shape { --r: 50px; clip-path: shape(from 0 0, hline to calc(50% - var(--r)), arc to calc(50% + var(--r)) 0 of 1%, hline to 100%, vline to 100%, hline to 0 ); }

When you define a small radius (smaller than half the distance between both points), no circle can meet the condition we explained earlier (an intersection with both points), so we cannot draw an arc. This case falls within an error handling where the browser will scale the radius until we can have a circle that meets the condition. Instead of considering this case as invalid, the browser will fix “our mistake” and draw an arc.

This error handling is pretty cool as it allows us to simplify our shape() function. Instead of specifying the exact radius, I simply put a small value and the browser will do the job for me. This trick only works when the arc we want to draw is half a circle. Don’t try to apply it with any arc command because it won’t always work.

Another optimization is to update the following:

arc to calc(50% + var(--r)) 0 of 1%,

…with this:

arc by calc(2 * var(--r)) 0 of 1%,

Almost all the commands can either use a to directive or a by directive. The first one defines absolute coordinates like the one we use with polygon(). It’s the exact position of the point we are moving to. The second defines relative coordinates which means we need to consider the previous point to identify the coordinates of the next point.

In our case, we are telling the arc to consider the previous point (50% - R) 0 and move by 2*R 0, so the final point will be (50% - R + 2R) (0 + 0), which is the same as (50% + R) 0.

.shape { --r: 50px; clip-path: shape(from 0 0, hline to calc(50% - var(--r)), arc by calc(2 * var(--r)) 0 of 1px, hline to 100%, vline to 100%, hline to 0 ); }

This last optimization is great because if we want to move the cutout from the center, we only need to update one value: the 50%.

.shape { --r: 50px; --p: 40%; clip-path: shape( from 0 0, hline to calc(var(--p) - var(--r)), arc by calc(2 * var(--r)) 0 of 1px, hline to 100%, vline to 100%, hline to 0 ); } CodePen Embed Fallback

How would you adjust the above to have the cut-out at the bottom, left, or right? That’s your first homework assignment! Try to do it before moving to the next part.

I will give my implementation so that you can compare with yours, but don’t cheat! If you can do this without referring to my work, you will be able to do more complex shapes more easily.

CodePen Embed Fallback Rounded Tab

Enough cut-out, let’s try to create a rounded tab:

Can you see the puzzle of this one? Similar to the previous shape, it’s a bunch of arc and line commands. Here is the code:

.shape { --r: 26px; clip-path: shape( /* left part */ from 0 100%, arc by var(--r) calc(-1 * var(--r)) of var(--r), vline to var(--r), arc by var(--r) calc(-1 * var(--r)) of var(--r) cw, /* right part */ hline to calc(100% - 2 * var(--r)), arc by var(--r) var(--r) of var(--r) cw, vline to calc(100% - var(--r)), arc by var(--r) var(--r) of var(--r) ); }

It looks a bit scary, but if you follow it command by command, it becomes a lot clearer to see what’s happening. Here is a figure to help you visualize the left part of it.

All the arc commands are using the by directive because, in all the cases, I always need to move by an offset equal to R, meaning I don’t have to calculate the coordinates of the points. And don’t try to replace the radius by 1% because it won’t work since we are drawing a quarter of a circle rather than half of a circle.

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From this, we can easily achieve the left and right variations:

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Notice how I am only using two arc commands instead of three. One rounded corner can be done with a classic border radius, so this can help us simplify the shape.

Inverted Radius

One last shape, the classic inner curve at the corner also called an inverted radius. How many arc commands do we need for this one? Check the figure below and think about it.

If your answer is six, you have chosen the difficult way to do it. It’s logical to think about six arcs since we have six curves, but three of them can be done with a simple border radius, so only three arcs are needed. Always take the time to analyze the shape you are creating. Sometimes, basic CSS properties can help with creating the shape.

What are you waiting for? This is your next homework and I won’t help you with a figure this time. You have all that you need to easily create it. If you are struggling, give the article another read and try to study the previous shapes more in depth.

Here is my implementation of the four variations:

CodePen Embed Fallback Conclusion

That’s all for this first part. You should have a good overview of the shape() function. We focused on the line and arc commands which are enough to create most of the common shapes.

Don’t forget to bookmark the SVG to CSS converter and keep an eye on my CSS Shape collection where you can find the code of all the shapes I create. And here is a last shape to end this article.

CodePen Embed Fallback Better CSS Shapes Using shape()

1. Lines and Arcs (you are here!)
2. More on Arcs
3. Curves

Better CSS Shapes Using shape() — Part 1: Lines and Arcs originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Clever, clever that Andy Bell. He shares a technique for displaying image alt text when the image fails to load. Well, more precisely, it’s a technique to apply styles to the alt when the image doesn’t load, offering a nice UI fallback for what would otherwise be a busted-looking error.

The recipe? First, make sure you’re using alt in the HTML. Then, a little JavaScript snippet that detects when an image fails to load:

const images = document.querySelectorAll("img"); if (images) { images.forEach((image) => { image.onerror = () => { image.setAttribute("data-img-loading-error", ""); }; }); }

That slaps an attribute on the image — data-img-loading-error — that is selected in CSS:

img[data-img-loading-error] { --img-border-style: 0.25em solid color-mix(in srgb, currentColor, transparent 75%); --img-border-space: 1em; border-inline-start: var(--img-border-style); border-block-end: var(--img-border-style); padding-inline-start: var(--img-border-space); padding-block: var(--img-border-space); max-width: 42ch; margin-inline: auto; }

And what you get is a lovely little presentation of the alt that looks a bit like a blockquote and is is only displayed when needed.

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Andy does note, however, that Safari does not render alt text if it goes beyond a single line, which &#x1f937;‍♂️.

You can style alt text like any other text originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Read the book, Typographic Firsts

A font-lover’s guide to numerals. All you ever needed to know about font numbers.

The post A Font Lover’s Guide to Numerals appeared first on I Love Typography.

In his AI Speaker Series presentation at Sutter Hill Ventures, David Soria Parra of Anthropic, shared insights on the Model-Context-Protocol (MCP), an open protocol designed to standardize how AI applications interact with external data sources and tools. Here's my notes from his talk:

• Models are only as good as the context provided to them, making it crucial to ensure they have access to relevant information for specific tasks
• MCP standardizes how AI applications interact with external systems, similar to how the Language Server Protocol (LSP) standardized development tools
• MCP is not a protocol between models and external systems, but between AI applications that use LLMs and external systems
• Without MCP, AI development is fragmented with every application building custom implementations, custom prompts, and custom tool calls
• MCP separates the concerns of providing data access from building applications
• This separation allows application developers to focus on building better applications while data providers can focus on exposing their data effectively

How MCP Works

• Two major components exist in an MCP system: client (implemented by the application using the LLM) and server (serves context to the client)
• MCP servers offer: Tools (functions that perform actions), Resources (raw data content exposed by the server), Prompts (show how tools should be invoked)
• Application developers can connect their apps to any MCP server in the ecosystem
• API developers can expose their data to multiple AI applications by implementing an MCP server once
• Allows different organizations within large companies to build components independently that work together through the protocol

Writing Good Tools for MCP

• Tools should be simple and focused on specific tasks
• Comprehensive descriptions help models understand when and how to use the tools
• Error messages should be in natural language to facilitate better interactions
• The goal is to create tools that are intuitive for both models and users

Future Directions for MCP

• Remote MCP servers with proper authorization mechanisms
• An official MCP registry to discover available servers and tools
• Asynchronous execution for long-running tasks
• Streaming data capabilities from servers to clients
• Namespacing to organize tools and resources
• Improved elicitation techniques for better interactions
• There's a need for a structure to manage the protocol as it grows

Shape master Temani Afif has what might be the largest collection of CSS shapes on the planet with all the tools to generate them on the fly. There’s a mix of clever techniques he’s typically used to make those shapes, many of which he’s covered here at CSS-Tricks over the years.

Some of the more complex shapes were commonly clipped with the path() function. That makes a lot of sense because it literally accepts SVG path coordinates that you can draw in an app like Figma and export.

But Temani has gone all-in on the newly-released shape() function which recently rolled out in both Chromium browsers and Safari. That includes a brand-new generator that converts path() shapes in shape() commands instead.

So, if we had a shape that was originally created with an SVG path, like this:

.shape { clip-path: path( M199.6,18.9 c-4.3-8.9-12.5-16.4-22.3-17.8 c-11.9-1.7-23.1,5.4-32.2,13.2 c-9.1,7.8-17.8,16.8-29.3,20.3 c-20.5,6.2-41.7-7.4-63.1-7.5 c38.7,27,24.8,33,15.2,43.3 c-35.5,38.2-0.1,99.4,40.6,116.2 c32.8,13.6,72.1,5.9,100.9-15 c27.4-19.9,44.3-54.9,47.4-88.6 c0.2-2.7,0.4-5.3,0.5-7.9 c204.8,38,203.9,27.8,199.6,18.9 z ); }

…the generator will spit this out:

.shape { clip-path: shape( from 97.54% 10.91%, curve by -10.93% -10.76% with -2.11% -5.38%/-6.13% -9.91%, curve by -15.78% 7.98% with -5.83% -1.03%/-11.32% 3.26%, curve by -14.36% 12.27% with -4.46% 4.71%/-8.72% 10.15%, curve by -30.93% -4.53% with -10.05% 3.75%/-20.44% -4.47%, curve to 7.15% 25.66% with 18.67% 15.81%/11.86% 19.43%, curve by 19.9% 70.23% with -17.4% 23.09%/-0.05% 60.08%, curve by 49.46% -9.07% with 16.08% 8.22%/35.34% 3.57%, curve by 23.23% -53.55% with 13.43% -12.03%/21.71% -33.18%, curve by 0.25% -4.77% with 0.1% -1.63%/0.2% -3.2%, curve to 97.54% 10.91% with 100.09% 22.46%/99.64% 16.29%, close ); }

Pretty cool!

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Honestly, I’m not sure how often I’ll need to convert path() to shape(). Seems like a stopgap sorta thing where the need for it dwindles over time as shape() is used more often — and it’s not like the existing path() function is broken or deprecated… it’s just different. But still, I’m using the generator a LOT as I try to wrap my head around shape() commands. Seeing the commands in context is invaluable which makes it an excellent learning tool.

SVG to CSS Shape Converter originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

A couple of days back, among the tens of crypto-scams that flood our contact inbox, we found an interesting question on nested lists from one of our readers.

I have a problem (related to list-numbering) that seems commonplace, but I can’t seem to solve it or find any solution for. If any of your geniuses can answer this, I’m sure there are going to be a lot of people interested.

Styling lists? Enough to catch my attention. After all, I just completed an entire guide about CSS counters. The message continues:

Here’s the problem. It’s a routine numbering sequence, of different levels, found in (for example) [government], legislation, and in my case, condominium bylaws. I have five levels represented by the first number at each level of 1., (1), (a) (lower-alpha), (i) (lower-roman), (A) (upper-alpha). Of course, I have 5 levels here, but if you could demonstrate a solution for 3 levels.

Fair enough! So, what we are looking to achieve is a nested list, where each sublist marker/counter is of a different kind. The example linked in the message is the following:

8 The strata corporation must repair and maintain all of the following: (a) common assets of the strata corporation; (b) common property that has not been designated as limited common property; (c) limited common property, but the duty to repair and maintain it is restricted to (i) repair and maintenance that in the ordinary course of events occurs less often than once a year, and (ii) the following, no matter how often the repair or maintenance ordinarily occurs: (A) the structure of a building; (B) the exterior of a building; (C) chimneys, stairs, balconies and other things attached to the exterior of a building; (D) doors, windows and skylights on the exterior of a building or that front on the common property;

While simple at first glance, it still has some nuance, so let’s try to come up with the most maintainable solution here.

The ugly way

My first approach to this problem was no approach at all; I just opened CodePen, wrote up the HTML, and tried to get my CSS to work towards the final result. After translating the Markdown into ol and li elements, and with no special styling on each list, the base list would look like the following:

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Once there, my first instinct was to select each ol element and then change its list-style-type to the desired one. To target each level, I selected each ol depending on its number of ol ancestors, then let the specificity handle the rest:

ol { list-style-type: decimal; /* Unnecessary; just for demo */ } ol ol { list-style-type: lower-alpha; } ol ol ol { list-style-type: lower-roman; } ol ol ol ol { list-style-type: upper-alpha; }

And as you can see, this works… But we can agree it’s an ugly way to go about it.

CodePen Embed Fallback Nesting to the rescue

Luckily, CSS nesting has been baseline for a couple of years now, so we could save ourselves a lot of ol selectors by just nesting each element inside the next one.

ol { list-style-type: decimal; ol { list-style-type: lower-alpha; ol { list-style-type: lower-roman; ol { list-style-type: upper-alpha; } } } }

While too much nesting is usually frowned upon, I think that, for this case in particular, it makes the CSS clearer on what it intends to do — especially since the CSS structure matches the HTML itself, and it also keeps all the list styles in one place. All to the same result:

CodePen Embed Fallback It’s legal

I don’t know anything about legal documents, nor do I intend to learn about them. However, I do know the law, and by extension, lawyers are finicky about how they are formatted because of legal technicalities and whatnot. The point is that for a legal document, those parentheses surrounding each list marker — like (A) or (ii) — are more than mere decoration and have to be included in our lists, which our current solution doesn’t.

A couple of years back, we would have needed to set a counter for each list and then include the parentheses along the counter() output; repetitive and ugly. Nowadays, we can use the @counter-style at rule, which as its name implies, allows us to create custom counter styles that can be used (among other places) in the list-style-type property.

In case you’re unfamiliar with the @counter-style syntax, what we need to know is that it can be used to extend predefined counter styles (like decimal or upper-alpha), and attach to them a different suffix or prefix. For example, the following counter style extends the common decimal style and adds a dash (-) as a prefix and a colon (:) as a suffix.

@counter-style my-counter-style { system: extends decimal; prefix: "- "; suffix: ": "; } ol { list-style-type: my-counter-style; } CodePen Embed Fallback

In our case, we’ll need four counter styles:

• A decimal marker, without the ending dot. The initial submission doesn’t make it clear if it’s with or without the dot, but let’s assume it’s without.
• A lower alpha marker, enclosed in parentheses.
• A lower Roman marker, also enclosed in parentheses.
• An upper alpha marker, enclosed in parentheses as well.

All these would translate to the following @counter-style rules:

@counter-style trimmed-decimal { system: extends decimal; suffix: " "; } @counter-style enclosed-lower-alpha { system: extends lower-alpha; prefix: "("; suffix: ") "; } @counter-style enclosed-lower-roman { system: extends lower-roman; prefix: "("; suffix: ") "; } @counter-style enclosed-upper-alpha { system: extends upper-alpha; prefix: "("; suffix: ") "; }

And then, we just gotta replace each with its equivalent in our initial ol declarations:

ol { list-style-type: trimmed-decimal; ol { list-style-type: enclosed-lower-alpha; ol { list-style-type: enclosed-lower-roman; ol { list-style-type: enclosed-upper-alpha; } } } } CodePen Embed Fallback It should work without CSS!

Remember, though, it’s a legal document, so what happens if the internet is weak enough so that only the HTML loads correctly, or if someone checks the page from an old browser that doesn’t support nesting or @counter-style?

Thinking only about the list, in most websites, it would be a mild annoyance where the markers go back to decimal, and you have to go by padding to know where each sublist starts. However, in a legal document, it can be a big deal. How big? I am no lawyer, so it beats me, but we still can make sure the list keeps its original numbering even without CSS.

For the task, we can use the HTML type attribute. It’s similar to CSS list-style-type but with its own limited uses. First, its use with ul elements is deprecated, while it can be used in ol elements to keep the lists correctly numbered even without CSS, like in legal or technical documents such as ours. It has the following values:

• "1" for decimal numbers (default)
• "a" for lowercase alphabetic
• "A" for uppercase alphabetic
• "i" for lowercase Roman numbers
• "I" for uppercase Roman numbers

Inside our HTML list, we would assign the correct numbering for each ol level:

CodePen Embed Fallback

Depending on how long the document is, it may be more the hassle than the benefit, but it is still good to know. Although this kind of document doesn’t change constantly, so it wouldn’t hurt to add this extra safety net.

Welp, that was kinda too much for a list! But that’s something intrinsic to legal documents. Still, I think it’s the simplest way to achieve the initial reader’s goal. Let me know in the comments if you think this is overengineered or if there is an easier way.

More on lists! Almanac on Apr 23, 2021 list-style ul { list-style: square outside none; } lists Sara Cope Almanac on Jan 28, 2025 @counter-style @counter-style apple-counter { ... } lists Juan Diego Rodríguez Article on May 30, 2025 Styling Counters in CSS lists Juan Diego Rodríguez

A Reader’s Question on Nested Lists originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Anyone that's gotten into a long chat with an AI model has likely noticed things slow down and results get worse the longer a conversation continues. Many chat interfaces will let people know when they've hit this point but background agents make the issue much less likely to happen.

Across all our AI-first companies, whether coding, engineering simulation, or knowledge work, a subset of people stay in one long chat session with AI models and never bother to create a new session when moving on to a new task. But... why does this matter? Long chat sessions mean lots of context which adds up to more tokens for AI models to process. The more tokens, the more time, the more cost, and eventually, the more degraded results get.

At the heart of this issue is a technical constraint called the context window. The context window refers to the amount of text, measured in tokens, that a large language model can consider or "remember" at one time. It functions as the AI's working memory, determining how long of a conversation an AI model can sustain without losing track of earlier details.

Starting a new chat session creates a new context window which helps a lot with this issue. So to encourage new sessions, many AI products will pop up a warning suggesting people to move on to a new chat when things start to bog down. Here's an example from Anthropic's Claude.

Warning messages like this aren't ideal but the alternative is inadvertently raking up costs and getting worse results when models try to makes sense of a long thread with many different topics. While AI systems can implement selective memory that prioritizes keeping the most relevant parts of the conversation, some things will need to get dropped to keep context windows manageable. And yes, bigger context windows can help but only to a point.

Background agents can help. AI products that make use of background agents encourage people to kick off a different agent for each of their discrete tasks. The mental model of "tell an agent to do something and come back to check its work" naturally guides people toward keeping distinct tasks separate and, as a result, does a lot to mitigate the context window issue.

The interface for our agent workspace for teams, Bench, illustrates this model. There's an input field to start new tasks and a list showing tasks that are still running, tasks awaiting review, and tasks that are complete. In this user interface model people are much more likely to kick off a new agent for each new task they need done.

Does this completely eliminate context window issues? Not entirely because agents can still fill a context window with the information they collect and use. People can also always give more and more instructions to an agent. But we've definitely seen that moving to a background agent UI model impacts how people approach working with AI models. People go from staying in one long chat session covering lots of different topics to firing off new agents for each distinct tasks they want to get done. And that helps a lot with context widow issues.

AI models are much better at writing prompts for AI models than people are. Which is why several of our AI-first companies rewrite people's initial prompts to produce better outcomes. Last week our AI for code company, Augment launched a similar approach that's significantly improved through its real time codebase understanding.

Since AI-powered agents can accomplish a lot more through the use of tools, guiding them effectively is critical. But most developers using AI for coding products write incomplete or vague prompts, which leads to incorrect or suboptimal outputs.

The Prompt Enhancer feature in Augment automatically pulls relevant context from a developer's codebase using Augment's real-time codebase index and the developer's current coding session. Augment uses its codebase understanding to rewrite the initial prompt, incorporating the gathered context and filling in missing details like files and symbols from the codebase. In many cases, the system knows what's in a large codebase better than a developer simply because it can keep it all "in its head" and track changes happening in real time.

Developers can review the enhanced prompt and edit it before executing. This gives them a chance to see how the system interpreted their request and make any necessary corrections.

As developers use this feature, they regularly learn what's possible with AI, what Augment understands and can do with its codebase understanding, and how to get the most out of both of these systems. It serves as an educational tool, helping developers become more proficient at working with AI coding tools over time.

We've used similar approaches in our image generation and knowledge agent products as well. By transforming vague or incomplete instructions into detailed, optimized prompts written by the systems that understand what's possible, we can make powerful AI tools more accessible and more effective.

Some weekend reading on the heels of Global Accessibility Awareness Day (GAADM), which took place yesterday. The Email Markup Consortium (EMC) released its 2025 study on the accessibility in HTML emails, and the TL;DR is not totally dissimilar from what we heard from WebAIM’s annual web report:

This is the third full year for this report and we are disappointed to see the same issues as we have in previous years. The top 10 issues haven’t changed order since last year, apart from the addition of color contrast, which can be put down to a change in the testing and reporting.

The results come from an analysis of 443,585 emails collected from the past year. According to EMC, only 21 emails passed all accessibility checks — and they were all written by the same author representing two different brands. And, further, that author represents one of the companies that not only sponsors the study, but develops the automated testing tool powering the analysis.

Automated testing is the key here. That’s needed for a project looking at hundreds of thousands of emails, but it won’t surface everything, as noted:

Email that pass our checks may still have accessibility issues that we cannot pick up through automated testing. For example, we check if an alt attribute is present on an image, but we do not check if the text is suitable for that image in the context of that message.

The most common issues relate to internationalization, like leaving out the lang (96% of emails) and dir (98% of emails) attributes. But you’ll be familiar with most of what rounds up the top 10, because it lines up with WebAIM’s findings:

• Links must have discernible text
• Element has insufficient color contrast
• Images must have alternate text
• Link text should be descriptive
• Links must be distinguishable without relying on color

I appreciate that the report sheds a light on what accessibility features are supported by specific email clients, such as Gmail. The report outlines a set of 20 HTML, CSS, and ARIA features they look for and found that only one email client (SFR Mail?) of the 44 evaluated supports all of the features. Apple Mail and Samsung Email are apparently close behind, but the other 41? Not so much.

So, yeah. Email has a ways to go, like a small microcosm of the web itself.

HTML Email Accessibility Report 2025 originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

I was reflecting on what I learned about CSS Carousels recently. There’s a lot they can do right out of the box (and some things they don’t) once you define a scroll container and hide the overflow.

Hey, isn’t there another fairly new CSS feature that works with scroll regions? Oh yes, that’s Scroll-Driven Animations. Shouldn’t that mean we can trigger an animation while scrolling through the items in a CSS carousel?

Why yes, that’s exactly what it means. At least in Chrome at the time I’m playing with this:

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It’s as straightforward as you might expect: define your keyframes and apply them on the carousel items:

@keyframes foo { from { height: 0; } to { height: 100%; font-size: calc(2vw + 1em); } } .carousel li { animation: foo linear both; animation-timeline: scroll(inline); }

There are more clever ways to animate these things of course. But what’s interesting to me is that this demo now combines CSS Carousels with Scroll-Driven Animations. The only rub is that the demo also slaps CSS Scroll Snapping in there with smooth scrolling, which is effectively wiped out when applying the scroll animation.

I thought I might work around that with a view() timeline instead. That certainly makes for a smoother animation that is applied to each carousel item as they scroll into view, but no dice on smooth scrolling.

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Scroll-Driven Animations Inside a CSS Carousel originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.