body {
  background: black;
}

.canvas {
  mix-blend-mode: screen;
}

.canvas, .background, .overlay {
  position: absolute;
  width: 100vw;
  height: 100vh;
}

.codepen-link {
  position: absolute;
  bottom: 30px;
  right: 30px;
  height: 40px;
  width: 40px;
  z-index: 10;
  border-radius: 50%;
  box-sizing: border-box;
  background-image: url("");
  background-position: center center;
  background-size: cover;
  opacity: 0.5;
  transition: all 0.25s;
}
.codepen-link:hover {
  opacity: 0.8;
  box-shadow: 0 0 6px #efefef;
}