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		var canvas = document.getElementById('stage');
		var context = canvas.getContext('2d');
		Math.randomRange = function (min, max) {
			return Math.floor(Math.random() * (max - min) + min);
		}
		var player = {
			x: 0,
			y: 300,
			width: 30,
			jumping: false,//标识是否跳跃中
			power: 0,//标识蓄力程度，决定跳多远
			speedY: 10//标识Y轴上的速度，模拟重力加速度
		}
		var gameover = false;
		var cameraMoving = false;//镜头是否移动中
		var timerPowerUp;//蓄力操作用的计时器
		var platforms = [];//存储所有生成的平台
		//初始化平台
		platforms.push({
			x: 0,
			width: 100
		}, {
			x: 200,
			width: 100
		});
		var lastPlatform = platforms[platforms.length - 1];//最新生成的平台
		var currentPlatform = platforms[0];//当前落脚的平台
		var drawPlayer = function () {
			context.fillStyle = "blue";
			context.save();
			context.fillRect(player.x, player.y, player.width, player.width);
			context.restore();
		}
		var drawPlatform = function () {
			context.fillStyle = "#A3A3A3";
			context.save();
			platforms.forEach(function (platform) {
				context.fillRect(platform.x, 300 + player.width, platform.width, 300);
			});
			context.restore();
		}
		var drawTextFailed=function() {
			if (gameover) {
				context.fillStyle = "#000";
				context.save();
				context.font = "normal 30px sans-serif";
				context.textBaseline = 'top';
				var text = "FAILED";
				context.fillText(text, canvas.clientWidth / 2 - text.length * 30 / 2, 300);
				context.restore();
			}
		}
		//玩家跳跃中
		var playerJumping = function () {
			if (player.jumping) {
				player.y -= player.speedY;
				player.speedY -= 0.7;
				player.x += player.power;
				if (player.y >= 300) {
					player.jumping = false;
					player.y = 300;
					player.power = 0;
					if (!iscurrentplatform()) {
						if(isfailed()){
							gameover=true;
						}else{
							currentPlatform = lastPlatform;
							generateNextPlatform();
							cameraMoving = true;
						}
					}
				}
			}
		}
		//生成下一个平台
		var generateNextPlatform = function () {
			var x = Math.randomRange(lastPlatform.x+100, 500);
			var width = Math.randomRange(player.width, 100);
			lastPlatform = {
				x: x,
				width: width
			}
			platforms.push(lastPlatform);
		}
		//判断玩家位置是否在当前平台
		var iscurrentplatform = function () {
			return player.x > currentPlatform.x - player.width && player.x < currentPlatform.x + currentPlatform.width;
		}
		//判断是否失败
		var isfailed = function () {
			return player.x <= (lastPlatform.x - player.width) || player.x >= (lastPlatform.x + lastPlatform.width);
		}
		//移动镜头(场景整体移动)
		var moveCamera = function () {
			if (cameraMoving) {
				player.x -= 10;
				platforms.forEach(function (platform) {
					platform.x -= 10;
				});
				if (player.x <= 0 || currentPlatform.x <= 0) {
					cameraMoving = false;
					if (player.x < 0) {
						player.x = 0;
					} else if (currentPlatform.x < 0) {
						currentPlatform.x = 0;
					}
				}
			}
		}
		//蓄力中
		var PowerUping = function () {
			player.power += 1;
		}
		//开始蓄力
		var PowerUp = function () {
			if (!gameover&&!player.jumping) {
				timerPowerUp = setInterval(PowerUping, 100);
			}
		}
		//停止蓄力
		var PowerUpStop = function () {
                        if (!gameover&&!player.jumping){
			clearInterval(timerPowerUp);
			player.jumping = true;
			player.speedY = 10;
                        }
		}
		//帧刷新时执行的其他操作
		var withFrameUpdate = function () {
			playerJumping();
			moveCamera();
		}
		//帧绘制
		var drawFrame = function () {
			window.requestAnimationFrame(drawFrame, canvas);
			context.clearRect(0, 0, canvas.width, canvas.height);
			drawPlayer();
			drawPlatform();
			drawTextFailed();
			withFrameUpdate();
		}
		document.addEventListener("mousedown", PowerUp);
		document.addEventListener("mouseup", PowerUpStop);
		drawFrame();

<body oncontextmenu="return false">
	<canvas id="stage" width="800" height="600"></canvas>
</body>