function saveCanvas() {
  saveCanvasButton.download = "image.png";
  saveCanvasButton.href = canvas
    .toDataURL("image/png")
    .replace("image/png", "image/octet-stream");
}

function goFullScreen() {
  if (canvas.requestFullScreen) canvas.requestFullScreen();
  else if (canvas.webkitRequestFullScreen) canvas.webkitRequestFullScreen();
  else if (canvas.mozRequestFullScreen) canvas.mozRequestFullScreen();
}