<input id="test" type="checkbox" />
<label for="test">Look at me!</label>

input[type="checkbox"]:checked {
  background: gray;
}

@media (pointer: fine) {
  input[type="checkbox"] {
    -moz-appearance: none;
    -webkit-appearance: none;
    appearance: none;
    width: 15px;
    height: 15px;
    border: 1px solid blue;
  }
}

@media (pointer: coarse) {
  input[type="checkbox"] {
    -moz-appearance: none;
    -webkit-appearance: none;
    appearance: none;
    width: 30px;
    height: 30px;
    border: 2px solid red;
  }
}