form {
  border: solid 1px #ccc;
  display: block;
  font-size: 2em;
  left: 50%;
  max-width: 20em;
  padding: 2em;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
}

/* hide on screen only so that other media see the standard checkbox */
@media screen {
  input[type=checkbox] {
    display: none;
  }
}
.fake-checkbox {
  border: solid .125em currentColor;
  box-sizing: border-box;
  display: inline-block;
  height: 1em;
  overflow: hidden;
  position: relative;
  top: .2em;
  width: 1em;
}
.fake-checkbox:before {
  background-color: #09f;
  bottom: -0.5em;
  content: "";
  height: 0;
  left: -0.5em;
  position: absolute;
  right: -0.5em;
  transition: all 1s ease-out;
}

:checked + .fake-checkbox:before {
  animation: oscillate 1s ease-out;
  height: calc(100% + 0.5em);
}

@keyframes oscillate {
  0%, 100% {
    transform: rotate(0);
  }
  33% {
    transform: rotate(5deg);
  }
  67% {
    transform: rotate(-5deg);
  }
}