body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
  margin: 0;
  overflow: hidden;
  background-color: #f0f0f0;
  overscroll-behavior: contain;
}
canvas {
  border: 1px solid #000;
  background-color: #fff;
  cursor: crosshair;
}