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>

var myGamePiece;

function startGame() {
    myGamePiece = new component(30, 30, "red", 80, 75);
    myGameArea.start();
}

function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.angle = 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();    
    }
}

function updateGameArea() {
    myGameArea.clear();
    myGamePiece.angle += 1 * Math.PI / 180;    
    myGamePiece.update();
}

</script>

<p>游戏区域每更新一次（每秒 50 次），红色方块就会旋转 1 度。</p>

<p>注意：angle 属性必须是弧度。您可以使用公式 x * Math.PI / 180 将度数转换为弧度。</p>

</body>
</html>