<!DOCTYPE html>
<html>
<head>
<style>
#clip {
  width: 100%;
  height: 300px;
  position: fixed;
  background-color: rgba(255, 0, 0, 0.9);
  -webkit-clip-path: polygon(0px 0px, 100% 0px, 100% 100%, 0px 83%);
  -webkit-backface-visibility: hidden;
  transform: translateY(100px);
}
</style>
</head>
<body>
  <div id="clip"></div>
</body>
</html>