html, body {
  height: 100%;
  overscroll-behavior: contain;
}

body {
  background: linear-gradient(to bottom, #000, #000018);
  margin: 0;
}

#sample {
  opacity: 0;
}

.entity {
  position: fixed;
}

.ball {
  position: absolute;
  background-color: #0f0;
  border: #0ff solid 5px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.square {
  position: absolute;
  background-color: #ff0;
}