diff --git a/src/game/mouse/space_invaders/alien.js b/src/game/mouse/space_invaders/alien.js
index 3d127a2..41e2419 100644
--- a/src/game/mouse/space_invaders/alien.js
+++ b/src/game/mouse/space_invaders/alien.js
@@ -4,8 +4,8 @@ class Alien extends Phaser.Sprite {
 		super();
 
 		this.isActivated = false;
+		this.isOnstage = false;
 		this.speedGrowing = Alien.DEFAULT_SPEED_SEC;
-		this.tweenScale = null;
 
 		this.initialX = initialX;
 		this.initialY = initialY;
@@ -15,7 +15,9 @@ class Alien extends Phaser.Sprite {
 
 		Phaser.Sprite.call(this, game, this.initialX, this.initialY, 'alien_normal');
 		this.anchor.set(0.5);
-		this.scale.set(Alien.MAX_SCALE);
+		// this.scale.set(Alien.MAX_SCALE);
+		this.setOnInitialPosition();
+
 
 		this.inputEnabled = true;
 		this.events.onInputOut.add(this.onOut, this);
@@ -28,24 +30,18 @@ class Alien extends Phaser.Sprite {
 	onOut() {
 		if(!this.isActivated)
 			return;
-
-		// console.log("onOut");
 	}
 
 	onOver() {
 		if(!this.isActivated)
 			return;
-
-		// console.log("onOver");
 	}
 
 	onDown() {
 		if(!this.isActivated)
 			return;
 
-		// console.log("onDown");
-
-		if(this.onFiredFunction)
+		if(typeof this.onFiredFunction !== "undefined")
 			this.onFiredFunction(this);
 	}
 
@@ -60,8 +56,13 @@ class Alien extends Phaser.Sprite {
 	}
 
 	shutdown() {
-		if(!this.tweenScale) {
-			this.tweenScale.stop();
+		if(typeof this.tweenScaleUp !== "undefined") {
+			this.tweenScaleUp.stop();
+			this.tweenScaleUp = null;
+		}
+		if(typeof this.tweenScaleDown !== "undefined") {
+			this.tweenScaleDown.stop();
+			this.tweenScaleDown = null;
 		}
 
 		this.scale.set(0);
@@ -73,7 +74,8 @@ class Alien extends Phaser.Sprite {
 		this.scale.set(Alien.MAX_SCALE);
 	}
 
-	moveOnStage() {
+	goOnstage() {
+		// set random position
 		let SPAWN_BOX_LEFT		= 100;
 		let SPAWN_BOX_WIDTH		= game.world.width - 200;
 		let SPAWN_BOX_TOP		= 300;
@@ -81,11 +83,28 @@ class Alien extends Phaser.Sprite {
 
 		this.x = SPAWN_BOX_LEFT + Math.random() * SPAWN_BOX_WIDTH;
 		this.y = SPAWN_BOX_TOP + Math.random() * SPAWN_BOX_HEIGHT;
+
+		// start scale tween animation
+		this.shutdown();
+
+		this.tweenScaleUp = game.add.tween(this.scale)
+			.to( { x: Alien.MAX_SCALE, y: Alien.MAX_SCALE }, Alien.DEFAULT_SPEED_SEC, Phaser.Easing.Linear.None, false);
+		this.tweenScaleDown = game.add.tween(this.scale)
+			.to( { x: 0, y: 0 }, Alien.DEFAULT_SPEED_SEC, Phaser.Easing.Linear.None, false);
+		this.tweenScaleUp.chain(this.tweenScaleDown);
+		this.tweenScaleDown.onComplete.addOnce(this.onEscaped, this);
+		this.tweenScaleUp.start();
+	}
+
+	onEscaped() {
+		if(!this.isActivated)
+			return;
+
+		if(typeof this.onEscapedFunction !== "undefined")
+			this.onEscapedFunction(this);
 	}
 
 }
 
-
-Alien.DEFAULT_SPEED_SEC		= 1000;
+Alien.DEFAULT_SPEED_SEC		= 3000;
 Alien.MAX_SCALE				= 3;
-
diff --git a/src/game/mouse/space_invaders/game.js b/src/game/mouse/space_invaders/game.js
index d40dea8..bc55688 100644
--- a/src/game/mouse/space_invaders/game.js
+++ b/src/game/mouse/space_invaders/game.js
@@ -24,18 +24,7 @@ class Game {
 			this.onAlienFired, this.onAlienEscaped
 		);
 		alien.setActive(true);
-		alien.moveOnStage();
-		/*
-		let alien = game.add.sprite(this.game.world.width / 2, this.game.world.height / 2, 'alien_normal');
-		alien.anchor.set(0.5);
-		alien.scale.set(0);
-
-		let alienTween = game.add.tween(alien.scale);
-		// alienTween.to( { x: 4, y: 4 }, 1000, Phaser.Easing.Linear.None, true, 0, -1, true);
-		// alienTween.yoyo(true, 3000);
-		alienTween.to( { x: 4, y: 4 }, 1000, Phaser.Easing.Linear.None, false);
-		alienTween.start();
-		*/
+		alien.goOnstage();
 
 
 		// bottom
@@ -87,11 +76,12 @@ class Game {
 
 	onAlienFired(sprite) {
 		console.log("onAlienFired");
-		sprite.moveOnStage();
+		sprite.goOnstage();
 	}
 
 	onAlienEscaped(sprite) {
 		console.log("onAlienEscaped");
+		// sprite.goOnstage();
 	}
 
 }
\ No newline at end of file