Space Blaster

I could not figure out how to add other levels so I would like some help on how that is done. I decided to keep the player skin the same in Level 3 because I wanted to make it more of a player reaching full power and thats what he looked like.

My modifications is that I added multiple enemies to make the 3 levels a bit harder. I also added asteroids in the playing field to make the player more aware and I changed the skin of the enemies in order to make them more different than each other and to represent the difficulty.