:root {
  --mouse-x: 0.5;
  --mouse-y: 1;
  --eye-height: 70;
}

.face {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 80px;
}

.eye {
  position: relative;
  width: 50px;
  height: calc(var(--eye-height) * 1px);
  border: 2px solid #111;
  background: #fefefe;
  border-radius: 50%;
  margin: 5px;
  overflow: hidden;
}

.eyeball {
  position: absolute;
  top: calc((min(var(--mouse-y) * 86, 43)) * 1px);
  left: calc(min(var(--mouse-x) * 24, 24) * 1px);
  height: 24px;
  width: 24px;
  background-color: #111;
  border-radius: 50%;
  display: inline-block;
}

.eyeball:after {
  content: "";
  display: inline-block;
  position: absolute;
  top: 2px;
  left: 7px;
  height: 8px;
  width: 8px;
  background-color: #fff;
  border-radius: 50%;
}