Very simple and fast paced. I find it easier to just avoid enemies than shooting. That's sad you had no time to add sounds :( I like that it's very clear what square is what.
even if I had time to add sound, I wouldn't have done it. The engine that I used isn't great with sound (It can't even loop music yet). Luckily there are plans to add a better sound API to this engine so maybe next jam I am able to add something to my game :)