2D Shooter Final

This is the 2D Shooter Project. There are some modifications compared to the first part:

- Level 3 (harder and more enemies).

- Add new background for menu and level 3.

- Set new background audio for each level.

- Display player lives under highscore.

- Add instructions.

In level 3:

- Add a spawner of enemy and asteroid.

- Add some environment component such as space stations, black holes,..

Created by Pham Hoang Duy (phamhoan@msu.edu)