落下するアニメーション

window.onload = function(){
  draw();
}
function draw(){
  var canvas = document.getElementById('mycanvas');
  if (!canvas || !canvas.getContext)return false;
  var ctx = canvas.getContext('2d');

  ctx.fillStyle = "red"
  var y = 0;

  (function loop(){
    ctx.clearRect(0,0,canvas.width, canvas.height);
    if (y > canvas.height) y = -50;
    y++;
    ctx.fillRect(0,y,50,50);
    setTimeout(loop,10);
  })();
}