1.container input {
2  position: absolute;
3  opacity: 0;
4  cursor: pointer;
5  height: 0;
6  width: 0;
7}
8
9.container {
10  position: relative;
11  cursor: pointer;
12  font-size: 17px;
13  width: 2em;
14  height: 2em;
15  border-radius: 50%;
16  user-select: none;
17  border: 5px solid white;
18  display: block;
19}
20
21.checkmark {
22  position: absolute;
23  top: 0;
24  left: 0;
25  width: 100%;
26  height: 100%;
27}
28
29.checkmark:after {
30  content: '';
31  position: absolute;
32  top: 25%;
33  left: 25%;
34  background-color: white;
35  width: 50%;
36  height: 50%;
37  border-radius: 50%;
38  transform: scale(0);
39  transition: 100ms ease;
40}
41
42.container input:checked ~ .checkmark:after {
43  transform: scale(1);
44}