For single player use W and S on the keyboard and space to shoot space bullets. try and eliminate as many aliens as you can (I am trying to make it in to real enemy waves) note that you may need to hit the aliens 1 or 2 times with the bullet for it to explode.
Sprite art and code was made by a human being who uses a dog in a donut for their profile picture... Check out my studio ---> https://scratch.mit.edu/studios/25196051/projects/ (Update 1 (9/19) Multiplayer is now working, but you will need to play on the same computer, point system will be added soon!