1.loader {
2  position: relative;
3  width: 300px;
4  height: 3px;
5  background: linear-gradient(to right, transparent, #28AE60, transparent);
6  overflow: hidden;
7}
8
9.loader::after {
10  content: '';
11  position: absolute;
12  translate: -200px 0;
13  width: 150px;
14  height: 100%;
15  background: linear-gradient(to right, transparent, #212121, transparent);
16  animation: slide 1s infinite;
17}
18
19@keyframes slide {
20  100% {
21    translate: 300px 0;
22  }
23}