===================================================================
--- original.js
+++ change.js
@@ -1,7 +1,18 @@
 /**** 
 * Classes
 ****/
+var LifePowerUp = Container.expand(function () {
+	var self = Container.call(this);
+	var powerUpGraphics = self.createAsset('lifePowerUp', 'Life Power Up', 0.5, 0.5);
+	self.speed = 2;
+	self.move = function () {
+		self.y += self.speed;
+		if (self.y > 2732 + self.height / 2) {
+			self.destroy();
+		}
+	};
+});
 // Define the EnemyBullet class
 var EnemyBullet = Container.expand(function () {
 	var self = Container.call(this);
 	var bulletGraphics = self.createAsset('enemyBullet', 'Enemy Bullet', 0.5, 0.5);
@@ -359,8 +370,16 @@
 				if (aliens[m].health <= 0) {
 					// Update score for destroying an alien
 					LK.setScore(LK.getScore() + 100);
 					scoreDisplay.updateScore(LK.getScore());
+					// Chance to drop a life power-up
+					if (Math.random() < 0.02) {
+						// 1 in 50 chance
+						var lifePowerUp = new LifePowerUp();
+						lifePowerUp.x = aliens[m].x;
+						lifePowerUp.y = aliens[m].y;
+						game.addChild(lifePowerUp);
+					}
 					aliens[m].destroy();
 					aliens.splice(m, 1);
 				}
 				// Destroy the hero bullet
@@ -395,8 +414,17 @@
 			aliens[o].destroy();
 			aliens.splice(o, 1);
 		}
 	}
+	// Pick up LifePowerUp
+	for (var p = 0; p < game.children.length; p++) {
+		var obj = game.children[p];
+		if (obj instanceof LifePowerUp && spaceRanger.intersects(obj)) {
+			spaceRanger.lives++;
+			livesDisplay.updateLives(spaceRanger.lives);
+			obj.destroy();
+		}
+	}
 	// Spawn enemies in waves
 	if (LK.ticks % waveInterval === 0 && meteors.length + aliens.length <= 2) {
 		for (var i = 0; i < enemiesPerWave; i++) {
 			var enemyTypes = [Meteor, Alien, EnemyType1, EnemyType2, EnemyType3, EnemyType4, EnemyType5];