===================================================================
--- original.js
+++ change.js
@@ -1,115 +1,139 @@
-/****
+/**** 
 * Classes
-****/
+****/ 
 // Bullet class
 var Bullet = Container.expand(function () {
-  var self = Container.call(this);
-  var bulletGraphics = self.attachAsset('bullet', {
-    anchorX: 0.5,
-    anchorY: 0.5
-  });
-  self.speed = -10;
-  self.update = function () {
-    self.y += self.speed;
-    if (self.y < -self.height) {
-      self.destroy();
-    }
-  };
+	var self = Container.call(this);
+	var bulletGraphics = self.attachAsset('bullet', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.speed = -10;
+	self.update = function () {
+		self.y += self.speed;
+		if (self.y < -self.height) {
+			self.destroy();
+		}
+	};
 });
 // Enemy class
 var Enemy = Container.expand(function () {
-  var self = Container.call(this);
-  var enemyGraphics = self.attachAsset('enemy', {
-    anchorX: 0.5,
-    anchorY: 0.5
-  });
-  self.speed = 2;
-  self.update = function () {
-    self.y += self.speed;
-    if (self.y > 2732) {
-      self.y = -self.height;
-    }
-  };
+	var self = Container.call(this);
+	var enemyGraphics = self.attachAsset('enemy', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.speed = 2;
+	self.update = function () {
+		self.y += self.speed;
+		if (self.y > 2732) {
+			self.y = -self.height;
+		}
+	};
 });
-//<Assets used in the game will automatically appear here>
 // Hero class
 var Hero = Container.expand(function () {
-  var self = Container.call(this);
-  var heroGraphics = self.attachAsset('hero', {
-    anchorX: 0.5,
-    anchorY: 0.5
-  });
-  self.speed = 5;
-  self.update = function () {
-    // Hero update logic
-  };
-  self.move = function (x, y, obj) {
-    self.x = x;
-    self.y = y;
-  };
+	var self = Container.call(this);
+	var heroGraphics = self.attachAsset('hero', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.speed = 5;
+	self.update = function () {
+		// Hero update logic
+		self.vy = (self.vy || 0) + 0.5; // gravity
+		self.y += self.vy;
+		for (var i = 0; i < platforms.length; i++) {
+			if (self.intersects(platforms[i]) && self.vy > 0) {
+				self.y = platforms[i].y - self.height / 2;
+				self.vy = 0;
+			}
+		}
+	};
+	self.down = function (x, y, obj) {
+		self.vy = -10; // jump
+	};
 });
+//<Assets used in the game will automatically appear here>
+// Platform class
+var Platform = Container.expand(function () {
+	var self = Container.call(this);
+	var platformGraphics = self.attachAsset('platform', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+});
 
-/****
+/**** 
 * Initialize Game
-****/
+****/ 
 var game = new LK.Game({
-  backgroundColor: 0x000000 //Init game with black background 
+	backgroundColor: 0x000000 //Init game with black background 
 });
 
-/****
+/**** 
 * Game Code
-****/
+****/ 
+// Initialize platforms
+var platforms = [];
+for (var i = 0; i < 5; i++) {
+	var platform = new Platform();
+	platform.x = Math.random() * 2048;
+	platform.y = Math.random() * 2732;
+	platforms.push(platform);
+	game.addChild(platform);
+}
 // Initialize hero
 var hero = new Hero();
 hero.x = 2048 / 2;
 hero.y = 2732 - 200;
 game.addChild(hero);
 // Initialize enemies
 var enemies = [];
 for (var i = 0; i < 5; i++) {
-  var enemy = new Enemy();
-  enemy.x = Math.random() * 2048;
-  enemy.y = Math.random() * -2732;
-  enemies.push(enemy);
-  game.addChild(enemy);
+	var enemy = new Enemy();
+	enemy.x = Math.random() * 2048;
+	enemy.y = Math.random() * -2732;
+	enemies.push(enemy);
+	game.addChild(enemy);
 }
 // Initialize bullets array
 var bullets = [];
 // Handle game move event
 game.move = function (x, y, obj) {
-  hero.move(x, y, obj);
+	hero.move(x, y, obj);
 };
 // Handle game down event
 game.down = function (x, y, obj) {
-  var bullet = new Bullet();
-  bullet.x = hero.x;
-  bullet.y = hero.y;
-  bullets.push(bullet);
-  game.addChild(bullet);
+	var bullet = new Bullet();
+	bullet.x = hero.x;
+	bullet.y = hero.y;
+	bullets.push(bullet);
+	game.addChild(bullet);
 };
 // Game update function
 game.update = function () {
-  // Update hero
-  hero.update();
-  // Update enemies
-  for (var i = 0; i < enemies.length; i++) {
-    enemies[i].update();
-    if (hero.intersects(enemies[i])) {
-      LK.effects.flashScreen(0xff0000, 1000);
-      LK.showGameOver();
-    }
-  }
-  // Update bullets
-  for (var j = bullets.length - 1; j >= 0; j--) {
-    bullets[j].update();
-    for (var k = enemies.length - 1; k >= 0; k--) {
-      if (bullets[j].intersects(enemies[k])) {
-        bullets[j].destroy();
-        bullets.splice(j, 1);
-        enemies[k].destroy();
-        enemies.splice(k, 1);
-        break;
-      }
-    }
-  }
+	// Update hero
+	hero.update();
+	// Update enemies
+	for (var i = 0; i < enemies.length; i++) {
+		enemies[i].update();
+		if (hero.intersects(enemies[i])) {
+			LK.effects.flashScreen(0xff0000, 1000);
+			LK.showGameOver();
+		}
+	}
+	// Update bullets
+	for (var j = bullets.length - 1; j >= 0; j--) {
+		bullets[j].update();
+		for (var k = enemies.length - 1; k >= 0; k--) {
+			if (bullets[j].intersects(enemies[k])) {
+				bullets[j].destroy();
+				bullets.splice(j, 1);
+				enemies[k].destroy();
+				enemies.splice(k, 1);
+				break;
+			}
+		}
+	}
 };
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