/game.html

## game.html
<html>
  <head>
    <title>Game</title>
    <script>
      var g, lt = Date.now();

      var scene = [];

      function step() {
        var ot = lt;
        var dt = (lt = Date.now()) - ot;

        var w = parseInt(g.canvas.width,10), h = parseInt(g.canvas.height,10);

        g.clearRect(0, 0, w, h);

        for (var i = 0; i < scene.length; i++) {
          scene[i].step(dt, w, h);
          scene[i].draw(g, w, h);
        }
        window.requestAnimationFrame(step);
      }

      var Character = function() {
        this.x = 20;
        this.y = 20;
        this.w = 20;
        this.h = 40;
        this.vx = 0;
        this.vy = 0;
      };

      Character.step = function(dt, width, height) {
        this.vy -= 9.8*dt/1000; // gravity
        if (this.y <= height-this.h) {
          this.vy = 0;
          this.y = height-this.h;
        }

        this.x += this.vx*dt/100;
        this.y += this.vy*dt/100;
      };

      Character.draw = function(g) {
        g.save();
        g.fillStyle = "#55f";
        g.fillRect(this.x, this.y, this.w, this.h);
        g.restore();
      };

      var LEFT_ARROW  = 39
        , UP_ARROW    = 40
        , DOWN_ARROW  = 41
        , RIGHT_ARROW = 42
        ;

      Character.keydown = function(e) {
        switch (e.keyCode) {
          case LEFT_ARROW:
            this.vx -= 3;
            break;
          case RIGHT_ARROW:
            this.vx += 3;
            break;
          case UP_ARROW:
            this.vy += 20;
            break;
        }
      };

      Character.keyup = function(e) {
        switch (e.keyCode) {
          case LEFT_ARROW:
            this.vx += 3;
            break;
          case RIGHT_ARROW:
            this.vx -= 3;
            break;
        }
      };

      window.onload = function() {
        window.onkeydown = function(e) {
          for (var i = 0; i < scene.length; i++) if (scene[i].keydown) scene[i].keydown(e);
        };

        window.onkeyup = function(e) {
          for (var i = 0; i < scene.length; i++) if (scene[i].keyup) scene[i].keyup(e);
        };

        g = document.getElementById("mainCanvas").getContext("2d");
        scene.push(new Character);
        window.requestAnimationFrame(step);

        window.onresize = function() {
          g.canvas.width = window.clientWidth;
          g.canvas.height = window.clientHeight;
        };
      };
    </script>
    <style>
      html, body {
        margin: 0;
        padding: 0;
        width: 100%;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <canvas id="mainCanvas" width="640" height="480"></canvas>
  </body>
</html>
	<html>
	<head>
	<title>Game</title>
	<script>
	var g, lt = Date.now();

	var scene = [];

	function step() {
	var ot = lt;
	var dt = (lt = Date.now()) - ot;

	var w = parseInt(g.canvas.width,10), h = parseInt(g.canvas.height,10);

	g.clearRect(0, 0, w, h);

	for (var i = 0; i < scene.length; i++) {
	scene[i].step(dt, w, h);
	scene[i].draw(g, w, h);
	}
	window.requestAnimationFrame(step);
	}

	var Character = function() {
	this.x = 20;
	this.y = 20;
	this.w = 20;
	this.h = 40;
	this.vx = 0;
	this.vy = 0;
	};

	Character.step = function(dt, width, height) {
	this.vy -= 9.8*dt/1000; // gravity
	if (this.y <= height-this.h) {
	this.vy = 0;
	this.y = height-this.h;
	}

	this.x += this.vx*dt/100;
	this.y += this.vy*dt/100;
	};

	Character.draw = function(g) {
	g.save();
	g.fillStyle = "#55f";
	g.fillRect(this.x, this.y, this.w, this.h);
	g.restore();
	};

	var LEFT_ARROW = 39
	, UP_ARROW = 40
	, DOWN_ARROW = 41
	, RIGHT_ARROW = 42
	;

	Character.keydown = function(e) {
	switch (e.keyCode) {
	case LEFT_ARROW:
	this.vx -= 3;
	break;
	case RIGHT_ARROW:
	this.vx += 3;
	break;
	case UP_ARROW:
	this.vy += 20;
	break;
	}
	};

	Character.keyup = function(e) {
	switch (e.keyCode) {
	case LEFT_ARROW:
	this.vx += 3;
	break;
	case RIGHT_ARROW:
	this.vx -= 3;
	break;
	}
	};

	window.onload = function() {
	window.onkeydown = function(e) {
	for (var i = 0; i < scene.length; i++) if (scene[i].keydown) scene[i].keydown(e);
	};

	window.onkeyup = function(e) {
	for (var i = 0; i < scene.length; i++) if (scene[i].keyup) scene[i].keyup(e);
	};

	g = document.getElementById("mainCanvas").getContext("2d");
	scene.push(new Character);
	window.requestAnimationFrame(step);

	window.onresize = function() {
	g.canvas.width = window.clientWidth;
	g.canvas.height = window.clientHeight;
	};
	};
	</script>
	<style>
	html, body {
	margin: 0;
	padding: 0;
	width: 100%;
	height: 100%;
	}
	</style>
	</head>
	<body>
	<canvas id="mainCanvas" width="640" height="480"></canvas>
	</body>
	</html>