html, body {
  height: 100%;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
}

.custom-checkbox {
  -webkit-appearance: none;
     -moz-appearance: none;
          appearance: none;
  position: relative;
  cursor: pointer;
  outline: none;
}
.custom-checkbox::before, .custom-checkbox::after {
  position: absolute;
  content: "";
  display: block;
  vertical-align: middle;
  border-radius: 100px;
  transition: all .3s;
}
.custom-checkbox::before {
  width: 150px;
  height: 100px;
  background: #666;
}
.custom-checkbox::after {
  width: 80px;
  height: 80px;
  top: 10px;
  left: 10px;
  background: #f66;
  box-shadow: 1px 1px 3px rgba(0, 0, 0, 0.5);
}
.custom-checkbox:checked::before {
  background: #555;
}
.custom-checkbox:checked::after {
  background: #5f5;
  -webkit-transform: translateX(50px);
          transform: translateX(50px);
}