W3School TIY Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>

<body onload="startGame()">

<script>

var myGamePiece;

function startGame() {
    myGamePiece = new component(30, 30, "red", 225, 225);
    myGameArea.start();
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
        window.addEventListener('keydown', function (e) {
            e.preventDefault();
            myGameArea.keys = (myGameArea.keys || []);
            myGameArea.keys[e.keyCode] = (e.type == "keydown");
        })
        window.addEventListener('keyup', function (e) {
            myGameArea.keys[e.keyCode] = (e.type == "keydown");
        })
    },
    stop : function() {
        clearInterval(this.interval);
    },    
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y, type) {

this.type = type;
    this.width = width;
    this.height = height;
    this.speed = 0;
    this.angle = 0;
    this.moveAngle = 0;
    this.x = x;
    this.y = y;    
    this.update = function() {
        ctx = myGameArea.context;
        ctx.save();
        ctx.translate(this.x, this.y);
        ctx.rotate(this.angle);
        ctx.fillStyle = color;
        ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);
        ctx.restore();    
    }
    this.newPos = function() {
        this.angle += this.moveAngle * Math.PI / 180;
        this.x += this.speed * Math.sin(this.angle);
        this.y -= this.speed * Math.cos(this.angle);
    }
}

function updateGameArea() {
    myGameArea.clear();
    myGamePiece.moveAngle = 0;
    myGamePiece.speed = 0;
    if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.moveAngle = -1; }
    if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.moveAngle = 1; }
    if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speed= 1; }
    if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speed= -1; }
    myGamePiece.newPos();
    myGamePiece.update();
}

</script>

<p>请确保游戏区域获得焦点，然后使用箭头键移动红色方块。</p>

</body>
</html>