CodePen

HTML

            
              <div class="container">
  <div class="toggle">
    <input type="checkbox">
    <span class="button"></span>
    <span class="label">+</span>
  </div>
  <div class="toggle">
    <input type="checkbox" checked>
    <span class="button"></span>
    <span class="label">–</span>
  </div>
</div>
            
          
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CSS

            
              
// Squishy buttons inspired by http://goo.gl/bFCyS

@import url(http://fonts.googleapis.com/css?family=Lato:700)

html, body

  font-family: 'Lato', sans-serif
  background: url(http://s.cdpn.io/1715/dark_stripes.png)
  text-align: center
  height: 100%

.container

  text-align: center
  position: absolute
  margin-top: -80px
  width: 100%
  top: 50%

.toggle

  margin: 4px
  display: inline-block

.toggle
  $size: 140px

  box-shadow: inset 0 0 35px 5px rgba(0,0,0,0.25), inset 0 2px 1px 1px rgba(255,255,255,0.9), inset 0 -2px 1px 0 rgba(0,0,0,0.25)
  border-radius: 8px
  background: #ccd0d4
  position: relative
  height: $size
  width: $size

  &:before

    $radius: $size * 0.845
    $glow: $size * 0.125

    box-shadow: 0 0 $glow $glow / 2 #fff
    border-radius: $radius
    background: #fff
    position: absolute
    margin-left: ( $radius - $glow ) * -0.5
    margin-top: ( $radius - $glow ) * -0.5
    opacity: 0.2
    content: ''
    height: $radius - $glow
    width: $radius - $glow
    left: 50%
    top: 50%

  .button

    $radius: $size * 0.688

    -webkit-filter: blur(1px)
    -moz-filter: blur(1px)
    filter: blur(1px)

    transition: all 300ms cubic-bezier(0.230, 1.000, 0.320, 1.000)
    box-shadow: 0 15px 25px -4px rgba(0,0,0,0.5), inset 0 -3px 4px -1px rgba(0,0,0,0.2), 0 -10px 15px -1px rgba(255,255,255,0.6), inset 0 3px 4px -1px rgba(255,255,255,0.2), inset 0 0 5px 1px rgba(255,255,255,0.8), inset 0 20px 30px 0 rgba(255,255,255,0.2)
    border-radius: $radius
    position: absolute
    background: #ccd0d4
    margin-left: $radius * -0.5
    margin-top: $radius * -0.5
    display: block
    height: $radius
    width: $radius
    left: 50%
    top: 50%

  .label

    transition: color 300ms ease-out
    text-shadow: 1px 1px 3px #ccd0d4, 0 0 0 rgba(0,0,0,0.8), 1px 1px 4px #fff
    line-height: $size - 1
    text-align: center
    position: absolute
    font-weight: 700
    font-size: 42px
    display: block
    opacity: 0.9
    height: 100%
    width: 100%
    color: rgba(0,0,0,0.4)

  input

    opacity: 0
    background :red
    position: absolute
    cursor: pointer
    z-index: 1
    height: 100%
    width: 100%
    left: 0
    top: 0

    &:active

      ~ .button

        box-shadow: 0 15px 25px -4px rgba(0,0,0,0.4), inset 0 -8px 30px 1px rgba(255,255,255,0.9), 0 -10px 15px -1px rgba(255,255,255,0.6), inset 0 8px 25px 0 rgba(0,0,0,0.4), inset 0 0 10px 1px rgba(255,255,255,0.6)
      
      ~ .label

        font-size: 40px
        color: rgba(0,0,0,0.45)

    &:checked
      
      ~ .button

        box-shadow: 0 15px 25px -4px rgba(0,0,0,0.4), inset 0 -8px 25px -1px rgba(255,255,255,0.9), 0 -10px 15px -1px rgba(255,255,255,0.6), inset 0 8px 20px 0 rgba(0,0,0,0.2), inset 0 0 5px 1px rgba(255,255,255,0.6)

      ~ .label

        font-size: 40px
        color: rgba(0,0,0,0.4)

            
          
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