Pure CSS accordion

by Dylan Schadeck

HTML

<h1>Pure CSS accordion</h1>

<!--
  - By using different combinations of `type="radio"`, `type="checkbox"`,
  - `name`, and `checked`, we can create accordions that only allow one
  - item to be open at once; accordions that can have any number of items
  - open at once; accordions that have specific items open by default.
  -->

<h2>One item open at once</h2>

<ul class="accordion">

    <li class="accordion__item">
        <label class="accordion__trigger" for="toggle-01">Lorem ipsum</label>
        <input type="radio" class="accordion__toggle" name="accordion-01" id="toggle-01" checked />
        <div class="accordion__target">
            <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p>
        </div>
    </li>

    <li class="accordion__item">
        <label class="accordion__trigger" for="toggle-02">Dolor sit amet</label>
        <input type="radio" class="accordion__toggle" name="accordion-01" id="toggle-02" />
        <div class="accordion__target">
            <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, commodo vitae, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus lacus enim ac dui. Donec non enim in turpis pulvinar facilisis. Ut felis. Praesent dapibus, neque id cursus faucibus, tortor neque egestas augue, eu vulputate magna eros eu erat. Aliquam erat volutpat. Nam dui mi, tincidunt quis, accumsan porttitor, facilisis luctus,...

SCSS

/**
 * A crude proof of concept for a pure CSS accordion.
 *
 * It makes use of the checkbox hack (note, *hack*), and could use some
 * attention regarding accessibility. Feel free to run with it.
 */


// Accessibly hide content:
// snook.ca/archives/html_and_css/hiding-content-for-accessibility
@mixin visually-hidden($state: hidden) {

    @if ($state == undo) {
        position: static;
        overflow: visible;
        width:  auto;
        height: auto;
        margin: auto;
        clip:   auto;
    }

    @else {
        border: 0;
        clip: rect(0 0 0 0);
        height: 1px;
        margin: -1px;
        overflow: hidden;
        padding: 0;
        position: absolute;
        width: 1px;
    }

}





/**
 * Housekeeping. Use something better in production.
 */
* {
    margin:  0;
    padding: 0;
    -webkit-box-sizing: border-box;
       -moz-box-sizing: border-box;
            box-sizing: border-box;
}

html {
    font-family: sans-serif;
    font-size: 75%;
    line-height: 1.5;
    padding: 1.5rem;
}

h1, h2 {
    margin-bottom: 1.5rem;
}




/**
 * Accordion component.
 */
.accordion {
    margin:  0;
    margin-bottom: 1.5rem;
    padding: 0;
    list-style: none;
}

    .accordion__item {
        border-bottom: 1px solid #fd665a;

        &:last-of-type {
            border-bottom: none;
        }

    }

        /**
         * The label element which triggers the open/close.
         */
        .accordion__trigger {
            display: block;
            background-color: #db4437;
            color: #fff;
            font-weight: bold;
            cursor: pointer;
            padding: 1.5rem;
        }

        /**
         * The radio/checkbox element needs to always be hidden.
         */
        .accordion__toggle {
            @include visually-hidden();
        }

        /**
         * Hide the accordion content.
         */
        .accordion__target {
            @include visually-hidden();
            background-color: #fd665a;
  ...