levels implemented

src/Airplane.java

src/ApexSlicer.java

src/Explosive.java

src/MegaSlicer.java

src/Projectile.java

src/RegularSlicer.java

src/ShadowDefend.java

src/Slicer.java

src/Sprite.java

src/SuperSlicer.java

src/SuperTank.java

src/Tank.java