I have never heard of this engine (OpenBOR) before, but it looks interesting.
The gameplay is awkward at first, but I eventually get the hang of it. It's very creative though, how you can shoot the enemies and it will bounce around, hitting other enemies in the process. I really like that idea.
I reached the boss but unfortunately I don't know how much HP it has left. I think some sort of HP bar is needed here. I hit it several times using the balls, and it seems like it damages it, but I don't know how far I have progressed.
The art is pretty good and clean. I like it.
The audio is also pretty nice. I like the music, and some of the SFX is pretty cute xD