It's.....well...."okay"
An average game all around. It doesn't do anything really good, but it also doesn't do anything really bad either. If you want my opinion on how to make the game better, I suggest starting out on level 1 with a slower enemy speed and work your way up to higher speeds. Just make sure the starting speed is faster than the original Space Invaders game. Some weapon power ups and repairable shields would also be pretty cool.(At least in my opinion:P) You should also add a LOT more levels. This is why I said you should start with a lower enemy speed, so you can work yourway up! Hope this helps:)