<!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", 80, 75);
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);
},
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) { 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>