.container input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
  height: 0;
  width: 0;
}

.container {
  display: block;
  position: relative;
  cursor: pointer;
  font-size: 20px;
  user-select: none;
}

.checkbox {
  background-color: transparent;
  padding: 12px;
  border-radius: 5px;
  border: grey solid 2px;
  box-shadow:
    4px 4px 9px black,
    inset 2px 2px 5px black,
    -1px -1px 5px rgba(68, 67, 67, 0.781),
    inset -1px -1px 5px rgba(66, 65, 65, 0.822);
  outline: none;
}

.container input:checked ~ .checkbox {
  background-color: transparent;
}
.checkbox:after {
  content: "";
  position: absolute;
  display: none;
}
.container input:checked ~ .checkbox:after {
  display: block;
}

.container .checkbox:after {
  left: 0.52em;
  top: 0.28em;
  width: 0.25em;
  height: 0.5em;
  border: solid gold;
  border-width: 0 0.15em 0.15em 0;
  transform: rotate(45deg);
}