1button {
2  position: relative;
3  background: none;
4  border: solid 1px #121212;
5  transition: linear 250ms;
6  width: 100px;
7  height: 40px;
8  display: flex;
9  justify-content: center;
10  align-items: center;
11  font-size: 1rem;
12}
13
14button:is(:hover,:focus) {
15  color: #fff;
16}
17
18button::after {
19  position: absolute;
20  content: '';
21  inset: 0;
22  z-index: -1;
23  background-color: #121212;
24  transform-origin: left;
25  transform: scaleX(0);
26  transition: linear 250ms;
27}
28
29button:is(:hover, :focus)::after {
30  transform: scale(1);
31}