html, body {
  margin: 0;
  height: 100%;
  background: #000;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

canvas {
  background: #000;
  box-shadow: 0 0 60px rgba(120, 130, 255, 0.2);
}

#fsBtn {
  position: fixed;
  top: 14px;
  right: 14px;
  z-index: 10;
  font-family: monospace;
  font-size: 12px;
  letter-spacing: 1px;
  color: #4ff0ff;
  background: rgba(10, 12, 30, 0.6);
  border: 1px solid rgba(79, 240, 255, 0.5);
  border-radius: 4px;
  padding: 6px 10px;
  cursor: pointer;
}

#fsBtn:hover {
  background: rgba(79, 240, 255, 0.15);
  border-color: #4ff0ff;
}