img {
  --_g: 10%/45% 45% no-repeat conic-gradient(#000 0 0);
  mask: 
    left   var(--_i,) top    var(--_g),
    bottom var(--_i,) left   var(--_g),
    top    var(--_i,) right  var(--_g),
    right  var(--_i,) bottom var(--_g);
  filter: grayscale();
  transition: .3s linear;
  cursor: pointer;
}
img:hover {
  --_i: 10%;
  filter: grayscale(0);
}

body {
  margin: 0;
  background: #c9697a;
  display: grid;
  min-height: 100vh;
  grid-auto-flow :column;
  place-content: center;
  gap: 40px;
}