2D Shooter Project

I added a second and a third level. The first level is the base we did in the course, i left it as a tutorial. The third level is a sort of infinity level with enemy spawners and a goal to kill 99 enemy.
I also made a boss enemy which is just a bullet sponge sadly.  But I also added others enemies like Aliens with own animations and sound and movement script.
Summary of added things over the base project:

-Alien enemy type with animation, sound, and behaviour,
-Spining Alien, same as the first but its spinning around.
-Boss enemy 

-Second and a third level

-New menu background image

-New scripts for Alien movement