2D Shooter

2D Shooter to test learning
Classic WASD to move the Ship, Mouse to aim and shot

- Added Instructions
- Full 3 mini levels more and more difficult from lvl 1 to 3
- Added new background (one sprite repeated only now)
- Added news ennemies and ennemies spawners
- Added planets and asteroid with collisions
- Added Thruster sprite animation to the player ship
- Change and adapted music's volumes