Cool game! I loved the classic video game feel with the graphics and sfx. It also had the punishing difficulty found in older games. Groovy theme song. Like others, I'd suggest feedback when you get hit (and fix the sound glitch on level two, yikes!) One of my favorite parts was the animation on the basic robots, how their legs moved and the swirls that came out of their feet.
All in all, great work. Keep it up!