“анимация кнопок CSS Codepen” Ответ

анимация кнопок CSS Codepen

.docBtn:after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(45deg, #00c897 50%, transparent 50%);
  z-index: -1;
  overflow: hidden;
  color: black;
}

.docBtn,
.docBtn:after {
  background-size: 300%;
  background-position: 100%;
  transition: 1s, font-size 0.2s;
}

.docBtn:hover,
.docBtn:hover:after {
  background-position: 0;
  font-size: 1.1em;
  border-radius: 100px;
  color: white;
}