body {
  margin: 0;
  padding: 0;
  background: #292929;
}

body.dark {
  background: white;
}

.center {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

input[type="checkbox"] {
  position: relative;
  width: 120px;
  height: 40px;
  -webkit-appearance: none;
  background: linear-gradient(0deg, #333, #000);
  outline: none;
  border-radius: 20px;
  box-shadow: 0 0 0 4px #353535, 0 0 0 5px #3e3e3e,
    inset 0 0 10px rgba(0, 0, 0, 1), 0 5px 20px rgba(0, 0, 0, 0.5),
    inset 0 0 15px rgba(0, 0, 0, 0.2);
}

input:checked[type="checkbox"] {
  background: linear-gradient(0deg, #6dd1ff, #20b7ff);
  box-shadow: 0 0 2px #6dd1ff, 0 0 0 4px #353535, 0 0 0 5px #3e3e3e,
    inset 0 0 10px rgba(0, 0, 0, 1), 0 5px 20px rgba(0, 0, 0, 0.5),
    inset 0 0 15px rgba(0, 0, 0, 0.2);
}

input[type="checkbox"]::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 80px;
  height: 40px;
  background: linear-gradient(0deg, #000, #6b6b6b);
  border-radius: 20px;
  box-shadow: 0 0 0 1px #232323;
  transform: scale(0.98, 0.96);
  transition: 0.5s;
}

input:checked[type="checkbox"]::before {
  left: 40px;
}

input[type="checkbox"]::after {
  content: "";
  position: absolute;
  top: calc(50% - 2px);
  left: 65px;
  width: 4px;
  height: 4px;
  background: linear-gradient(0deg, #6b6b6b, #000);
  border-radius: 50%;
  transition: 0.5s;
}

input:checked[type="checkbox"]::after {
  background: #63cdff;
  box-shadow: 0 0 5px #13b3ff, 0 0 15px #13b3ff;
  left: 105px;
}