<div>
  <label>
    <input type="checkbox" class="option-input checkbox" CHECKED />
    Checkbox
  </label>
  <label>
    <input type="checkbox" class="option-input checkbox" />
    Checkbox
  </label>
  <label>
    <input type="checkbox" class="option-input checkbox" />
    Checkbox
  </label>
</div>
<div>
  <label>
    <input type="radio" class="option-input radio" name="example" />
    Radio option
  </label>
  <label>
    <input type="radio" class="option-input radio" name="example" />
    Radio option
  </label>
  <label>
    <input type="radio" class="option-input radio" name="example" />
    Radio option
  </label>
</div>

@import "bourbon";

// options
$option-color:           #cbd1d8;
$checked-option-color:   #40e0d0;
$option-size:            40px;
$explosion-distance:     5; // multiplied by $option-size
$explosion-duration:     0.65s;

// on-click animation
@include keyframes(click-wave) {
  $offset: ((($option-size * $explosion-distance) - $option-size) / 2);
  
  0% {
    @include size($option-size);
    opacity: 0.35;
    position: relative;
  }
  
  100% {
    @include size($option-size*$explosion-distance);
    margin-left: -$offset;
    margin-top: -$offset;
    opacity: 0;
  }
}

// Checkbox/Radio replacement
.option-input {
  @include appearance(none);
  @include position($option-size/3 0 0 0);
  @include size($option-size);
  @include transition;
  background: $option-color;
  border: none;
  color: #fff;
  cursor: pointer;
  display: inline-block;
  margin-right: 0.5rem;
  outline: none;
  position: relative;
  z-index: 1000;

  &:hover {
    background: darken($option-color, 15%);
  }

  &:checked {
    background: $checked-option-color;

    // checkmark
    &::before {
      @include size($option-size);
      @include position(absolute);
      content: '\2716';
      display: inline-block;
      font-size: $option-size/1.5;
      text-align: center;
      line-height: $option-size;
    }

    // animted wave
    &::after {
      @include animation(click-wave $explosion-duration);
      background: $checked-option-color;
      content: '';
      display: block;
      position: relative;
      z-index: 100;
    }
  }
  
  &.radio {
    border-radius: 50%;    

    &::after {
      border-radius: 50%;
    }
  }
}

// Demo styles
body {
  @include box(horizontal, start, stretch);
  background: #e8ebee;
  color: darken($option-color, 15%);
  font-family: $helvetica;
  text-align: center;
  
  div {
    padding: 5rem;
  }

  label {
    display: block;
    line-height: $option-size;
  }
}