public void enterScreen(int id){
		previousScreen = currentScreen;
		if(currentScreen != null){
			currentScreen.hide();
		}
		currentScreen = screens.get(id);
		currentScreen.show();
		
		if(previousScreen != null && previousScreen instanceof GameScreen){
			GameScreen prevGameScreen = (GameScreen) previousScreen;
			prevGameScreen.startOutTransition(currentScreen);
		}
		if(currentScreen instanceof GameScreen){
			GameScreen currGameScreen = (GameScreen) currentScreen;
			currGameScreen.startInTransition(previousScreen);
		}
	}