I enjoyed it. I liked the variety of enemies / shooting behavior. And the minimap was a nice and helpful touch. I also appreciated how fast the movement and progression was.
On the other hand, some things were too fast - I couldn't fully read the level descriptions and I accidentally skipped the ending instantly with a button press. Once I realized that shooting the enemies was optional, I mostly ignored the fact that I could shoot for the rest of the game. Now take that criticism and throw it out because it's a game jam and you done good.