html, body {
  margin: 0;
  padding: 0;
  overflow: hidden;
  background: black;
}

#matrix {
  position: absolute;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
}

#mask {
  position: absolute;
  width: 380px;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  opacity: 0;
  transition: opacity 2s ease-in-out;
  pointer-events: none;
  filter: drop-shadow(0 0 20px red);
}