Globally, the media control icons are some of the most universally understood visual language in any kind of interface. A designer can simply assume that every user not only knows ▶️ = play, but that users will seek out the icon in order to watch any video or animation.

Reportedly introduced in the 1960s by Swedish engineer Philip Olsson the play arrow was first designed to indicate the direction where the tape would go when reading on reel-to-reel tape players. Since then, we switched from cassettes to CDs, from the iPod to Spotify, but the media controls icons remain the same.

The play ▶️ icon is standard symbol (with its own unicode) of starting an audio/video media along with the rest of the symbols like stop, pause, fast-forward, rewind, and others.

There are unicode and emoji options for play button icons, but if you wanted something custom, you might reach for an icon font or custom asset. But what if you want to shift between the icons? Can that change be smooth? One solution could be to use SVG. But what if it could be done in 10 lines of CSS? How neat is that‽

In this article, we’ll build both a play button and a pause button with CSS and then explore how we can use CSS transitions to animate between them.

Play Button

Step one

We want to achieve a triangle pointing right. Let’s start by making a box with a thick border. Currently, boxes are the preferred base method to make triangles. We’ll start with a thick border and bright colors to help us see our changes.

<button class='button play'></button>

.button.play { width: 74px; height: 74px; border-style: solid; border-width: 37px; border-color: #202020; }

Step two

Rendering a solid color border yields the above result. Hidden behind the color of the border is a neat little trick. How is the border being rendered exactly? Let’s change the border colors, one for each side, will help us see how the border is rendered.

.button.play { ... border-width: 37px 37px 37px 37px; border-color: red blue green yellow; }

Step three

At the intersection of each border, you will notice that a 45-degree angle forms. This is an interesting way that borders are rendered by a browser and, hence, open the possibility of different shapes, like triangles. As we’ll see below, if we make the border-left wide enough, it looks as if we might achieve a triangle!

.button.play { ... border-width: 37px 0px 37px 74px; border-color: red blue green yellow; }

Step four

Well, that didn’t work as expected. It is as if the inner box (the actual div) insisted on keeping its width. The reason has to do with the box-sizing property, which defaults to a value of content-box . The value content-box tells the div to place any border on the outside, increasing the width or height.

If we change this value to border-box , the border is added to the inside of the box.

.button.play { ... box-sizing: border-box; width: 74px; height: 74px; border-width: 37px 0px 37px 74px; }

Final step

Now we have a proper triangle. Next, we need to get rid of the top and bottom part (red and green). We do this by setting the border-color of those sides to transparent . The width also gives us control over the shape and size of the triangle.

.button.play { ... border-color: transparent transparent transparent #202020; }

Here’s an animation to explain that, if that’s helpful.

Pause Button

Step one

We’ll continue making our pause symbol by starting with another thick-bordered box since the previous one worked so well.

<button class='button pause'></button>

.button.pause { width: 74px; height: 74px; border-style: solid; border-width: 37px; border-color: #202020; }

Step two

This time we’ll be using another CSS property to achieve the desired result of two parallel lines. We’ll change the border-style to double . The double property in border-style is fairly straightforward, doubles the border by adding a transparent stroke in between. The stroke or empty gap will be 33% of the given border width.

.button.pause { ... border-style: double; border-width: 0px 37px 0px 37px; }

Final step

border-width

.button.pause{ ... border-width: 0px 0px 0px 37px; border-color: #202020; }

Animating the Transition

border-width property. Using theis what will make the transition work smoothly in the next step.

In the two buttons we created above, notice that there are a lot of similarities, but two differences: border-width and border-style . If we use CSS transitions we can shift between the two symbols. There’s no transition effect for border-style but border-width works great.

A pause class toggle will now animate between the play and pause state.

Here’s the final style in SCSS:

.button { box-sizing: border-box; height: 74px; border-color: transparent transparent transparent #202020; transition: 100ms all ease; will-change: border-width; cursor: pointer; // play state border-style: solid; border-width: 37px 0 37px 60px; // paused state &.pause { border-style: double; border-width: 0px 0 0px 60px; } }

Demo

See the Pen Button Transition with Borders by Chris Coyier (@chriscoyier) on CodePen.

Toggling without JavaScript

With a real-world play/pause button, it’s nearly certain you’ll be using JavaScript to toggle the state of the button. But it’s interesting to know there is a CSS way to do it, utilizing an input and label: the checkbox hack.

<div class="play-pause"> <input type="checkbox" value="" id="playPauseCheckbox" name="playPauseCheckbox" /> <label for="playPauseCheckbox"></label> </div>

.playpause { label { display: block; box-sizing: border-box; width: 0; height: 74px; cursor: pointer; border-color: transparent transparent transparent #202020; transition: 100ms all ease; will-change: border-width; // paused state border-style: double; border-width: 0px 0 0px 60px; } input[type='checkbox'] { visibility: hidden; &:checked + label { // play state border-style: solid; border-width: 37px 0 37px 60px; } } }

Demo

See the Pen Toggle Button with Checkbox by Chris Coyier (@chriscoyier) on CodePen.

I would love your thoughts and feedback. Please add them in the comments below.