<div class="box"></div>

.box {
  width: 200px;
  aspect-ratio: 1.5;
  display: inline-block;
  background: linear-gradient(45deg,red,blue);
  -webkit-mask: radial-gradient(30px at 30px 30px,#0000 98%,#000);
  transition: .3s;
  cursor: pointer;
}
.box:hover {
  -webkit-mask: radial-gradient(30px at 30px 30px,#0000 98%,#000) -30px -30px;
  
}