* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}
body {
  font-family: sans-serif;
  font-size: 24px;
  background-color: #333;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
}

a {
  text-decoration: none;
  text-transform: uppercase;
  background-color: yellowgreen;
  display: inline-block;
  border-radius: 3px;
  box-shadow: 2px 2px 6px rgba(0, 0, 0, 0.3);

  position: relative;
  width: 10rem;
  height: 4rem;
}

a span {
  position: absolute;
  display: inline-block;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #eee;
  border-radius: 3px;
  transition: all 0.3s;
}

a span:last-child {
  background-color: #eee;
  color: yellowgreen;

  clip-path: polygon(0 0, 100% 0%, 100% 100%, 0 100%, 0 48%);
}
a:hover span:last-child {
  clip-path: polygon(60% 0, 100% 0%, 100% 100%, 60% 100%, 50% 50%);
}