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我在畫布上有一個矩形（應該出現），我想從畫布的一側移動到另一側。然而，我擁有atm的代碼並沒有工作，因爲沒有任何東西顯示出來！任何幫助將不勝感激，歡呼！動畫畫布
<!DOCTYPE html>
<html>
<head>
<title>Simple animations in HTML5</title>
<!--<script>
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
context.fillStyle = "blue";
context.fillRect (20, 50, 200, 100);
</script> -->
<script>
function drawMessage()
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
context.fillStyle = "blue";
context.fillRect(x, y, WIDTH, HEIGHT);
context.fillStyle = "white";
context.font = "30px Arial";
context.fillText ("Hello World", MESSAGE_WIDTH, MESSAGE_HEIGHT);
x += dx;
y += dy;
if(x <= 0 || x >= 500)
{
dx = -dx;
}
if(y <= 0 || y >= 200)
{
dy = -dy
}
function animate()
{
return setInterval(drawMessage, 10);
}
</script>
</head>
<body>
<h2> Optical Illusion </h2>
<video id="illusion" width="640" height="480" controls>
<source src="Illusion_movie.ogg">
</video>
<div id="buttonbar">
<button onclick="changeSize()">Big/Small</button>
</div>
<p>
Watch the animation for 1 minute, staring at the centre of the image. Then look at something else near you.
For a few seconds everything will appear to distort.
Source: <a href="http://en.wikipedia.org/wiki/File:Illusion_movie.ogg">Wikipedia:Illusion movie</a>
</p>
<script type="text/javascript">
var myVideo=document.getElementById("illusion");
var littleSize = false;
function changeSize()
{
myVideo.width = littleSize ? 800 : 400;
littleSize = !littleSize;//toggle boolean
}
</script>
<canvas id="myCanvas" width="500" height="500">
</canvas>
<!--<script type="text/javascript">
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
context.fillStyle = "blue";
context.fillRect(20, 50, 200, 100);
context.fillStyle = "white";
context.font = "30px Arial";
context.fillText ("Hello World", 35, 110);
</script> -->
<script>
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var x = 20; // x coordinate of box position
var y = 50; // y coordinate of box position
var dx = 2; // amount to move box to the right
var dy = 4; // amount to move box down
var WIDTH = 500; // width of canvas
var HEIGHT = 200; // height of canvas
var MESSAGE_WIDTH = 200; // width of message
var MESSAGE_HEIGHT = 100; // height of message
animate(); // run the animation
</script>
</body>
</html>