CSS-+-HTML-only-Accordion-Element.markdown

CSS + HTML only Accordion Element

Read the copy in the accordion sections for some info about how this was made.

A Pen by Alex Bergin on CodePen.

License.

index.html

<h1>CSS + HTML only Accordion Element</h1>
<ul>
  <li>
    <input type="checkbox" checked>
    <i></i>
    <h2>Languages Used</h2>
    <p>This page was written in HTML and CSS. The CSS was compiled from SASS. I used Normalize as my CSS reset and -prefix-free to save myself some headaches. I haven't quite gotten the hang of Slim for compiling into HTML, but someday I'll use it since its syntax compliments that of SASS. Regardless, this could all be done in plain HTML and CSS.</p>
  </li>
  <li>
    <input type="checkbox" checked>
    <i></i>
    <h2>How it Works</h2>
    <p>Using the sibling and checked selectors, we can determine the styling of sibling elements based on the checked state of the checkbox input element. One use, as demonstrated here, is an entirely CSS and HTML accordion element. Media queries are used to make the element responsive to different screen sizes.</p>
  </li>
  <li>
    <input type="checkbox" checked>
    <i></i>
    <h2>Points of Interest</h2>
    <p>By making the open state default for when :checked isn't detected, we can make this system accessable for browsers that don't recognize :checked. The fallback is simply an open accordion. The accordion can be manipulated with Javascript (if needed) by changing the "checked" property of the input element.</p>
  </li>
</ul>

style.sass

$white: rgba(254,255,250,1)
$grey: rgba(220,231,235,1)
$red: rgba(255,104,115,1)
$black: rgba(48,69,92,0.8)
$sans: 'Titillium Web', sans-serif
  
.transition
  transition: all 0.25s ease-in-out

.flipIn
  animation: flipdown 0.5s ease both
    
.no-select
  -webkit-tap-highlight-color: rgba(0,0,0,0)
  -webkit-touch-callout: none
  -webkit-user-select: none
  -khtml-user-select: none
  -moz-user-select: none
  -ms-user-select: none
  user-select: none

html
  width: 100%
  height: 100%
  perspective: 900
  overflow-y: scroll
  background-color: $grey
  font-family: $sans
  color: $black
  
body
  min-height: 0
  display: inline-block
  position: relative
  left: 50%
  margin: 90px 0
  transform: translate( -50% , 0 )
  box-shadow: 0 10px 0 0 $red inset
  background-color: $white
  max-width: 450px
  padding: 30px
  
  @media ( max-width:550px )
    box-sizing: border-box
    transform: translate( 0 , 0 )
    max-width: 100%
    min-height: 100%
    margin: 0
    left: 0

h1 , h2
  color: $red

h1
  text-transform: uppercase
  font-size: 36px
  line-height: 42px
  letter-spacing: 3px
  font-weight: 100
  @extend .flipIn
  
h2
  font-size: 26px
  line-height: 34px
  font-weight: 300
  letter-spacing: 1px
  display: block
  background-color: $white
  margin: 0
  cursor: pointer
  @extend .no-select

p
  color: $black
  font-size: 17px
  line-height: 26px
  letter-spacing: 1px
  position: relative
  overflow: hidden
  max-height: 800px
  @extend .transition
  opacity: 1
  transform: translate( 0 , 0 )  
  margin-top: 14px
  z-index: 2
  
ul
  list-style: none
  perspective: 900
  padding: 0
  margin: 0
  
  li
    position: relative
    padding: 0
    margin: 0
    padding-bottom: 4px
    padding-top: 18px
    border-top: 1px dotted $grey
    @extend .flipIn
      
    &:nth-of-type(1)
      animation-delay: 0.5s
    
    &:nth-of-type(2)
      animation-delay: 0.75s
        
    &:nth-of-type(3)
      animation-delay: 1.0s
    
    &:last-of-type
      padding-bottom: 0
      
    i
      position: absolute
      transform: translate( -6px , 0 )
      margin-top: 16px
      right: 0
      
      &:before , &:after
        content: ""
        @extend .transition
        position: absolute
        background-color: $red
        width: 3px
        height: 9px
        
      &:before
        transform: translate( -2px , 0 ) rotate( 45deg )
          
      &:after
        transform: translate( 2px , 0 ) rotate( -45deg )
    
    input[type=checkbox]
      position: absolute
      cursor: pointer
      width: 100%
      height: 100%
      z-index: 1
      opacity: 0
      
      &:checked
        &~p
          margin-top: 0
          max-height: 0
          opacity: 0
          transform: translate( 0 , 50% )
            
        &~i
          &:before
            transform: translate( 2px , 0 ) rotate( 45deg )
          
          &:after
            transform: translate( -2px , 0 ) rotate( -45deg )

@keyframes flipdown
  0%
    opacity: 0
    transform-origin: top center
    transform: rotateX(-90deg)
  5%
    opacity: 1
  80%
    transform: rotateX(8deg)
  83%
    transform: rotateX(6deg)
  92%
    transform: rotateX(-3deg)
  100%
    transform-origin: top center
    transform: rotateX(0deg)