components/paper-checkbox/paper-checkbox.css

/*
Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/

:host {
  display: inline-block;
  white-space: nowrap;
}

:host(:focus) {
  outline: none;
}

#checkboxContainer {
  position: relative;
  width: 18px;
  height: 18px;
  cursor: pointer;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
}

#checkboxContainer.labeled {
  display: inline-block;
  vertical-align: middle;
}

#ink {
  position: absolute;
  top: -15px;
  left: -15px;
  width: 48px;
  height: 48px;
  color: #5a5f5a;
}

#ink[checked] {
  color: #0f9d58;
}

#checkbox {
  position: absolute;
  box-sizing: border-box;
  top: 0px;
  left: 0px;
  width: 18px;
  height: 18px;
  border: solid 2px;
  border-color: #5a5a5a;
  pointer-events: none;
}

/* checkbox checked animations */
#checkbox.checked.box {
  border: solid 2px;
  -webkit-animation: box-shrink 140ms ease-out forwards;
  animation: box-shrink 140ms ease-out forwards;
}

@-webkit-keyframes box-shrink {
  0% {
    -webkit-transform: rotate(0deg);
    top: 0px;
    left: 0px;
    width: 18px;
    height: 18px;
  }
  100% {
    -webkit-transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
}

@keyframes box-shrink {
  0% {
    transform: rotate(0deg);
    top: 0px;
    left: 0px;
    width: 18px;
    height: 18px;
  }
  100% {
    transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
}

#checkbox.checked.checkmark {
  border-left: none;
  border-top: none;
  -webkit-animation: checkmark-expand 140ms ease-out forwards;
  animation: checkmark-expand 140ms ease-out forwards;
}

@-webkit-keyframes checkmark-expand {
  0% {
    -webkit-transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
  100% {
    -webkit-transform: rotate(45deg);
    top: -4px;
    left: 6px;
    width: 10px;
    height: 21px;
    border-right-width: 2px;
    border-bottom-width: 2px;
  }
}

@keyframes checkmark-expand {
  0% {
    transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
  100% {
    transform: rotate(45deg);
    top: -4px;
    left: 6px;
    width: 10px;
    height: 21px;
    border-right-width: 2px;
    border-bottom-width: 2px;
  }
}

#checkbox.checked {
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
  top: -4px;
  left: 6px;
  width: 10px;
  height: 21px;
  border-top: none;
  border-left: none;
  border-right-width: 2px;
  border-bottom-width: 2px;
  border-color: #0f9d58;
}

/* checkbox unchecked animations */
#checkbox.unchecked.checkmark {
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
  border-left: none;
  border-top: none;
  -webkit-animation: checkmark-shrink 140ms ease-out forwards;
  animation: checkmark-shrink 140ms ease-out forwards;
}

@-webkit-keyframes checkmark-shrink {
  0% {
    top: -4px;
    left: 6px;
    width: 10px;
    height: 21px;
    border-right-width: 2px;
    border-bottom-width: 2px;
  }
  100% {
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
}

@keyframes checkmark-shrink {
  0% {
    top: -4px;
    left: 6px;
    width: 10px;
    height: 21px;
    border-right-width: 2px;
    border-bottom-width: 2px;
  }
  100% {
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
}

#checkbox.unchecked.box {
  -webkit-animation: box-expand 140ms ease-out forwards;
  animation: box-expand 140ms ease-out forwards;
}

@-webkit-keyframes box-expand {
  0% {
    -webkit-transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
  100% {
    -webkit-transform: rotate(0deg);
    top: 0px;
    left: 0px;
    width: 18px;
    height: 18px;
  }
}

@keyframes box-expand {
  0% {
    transform: rotate(45deg);
    top: 13px;
    left: 5px;
    width: 4px;
    height: 4px;
  }
  100% {
    transform: rotate(0deg);
    top: 0px;
    left: 0px;
    width: 18px;
    height: 18px;
  }
}

/* label */
#checkboxLabel {
  position: relative;
  display: inline-block;
  vertical-align: middle;
  padding-left: 8px;
  white-space: normal;
  pointer-events: none;
}

#checkboxLabel[hidden] {
  display: none;
}

/* disabled state */
:host([disabled]) {
  pointer-events: none;
}

:host([disabled]) #checkbox {
  border-color: #eaeaea !important;
}