It looks like I have problems with collision between bullets and enemies, I don't if it's the game or it's my pc, I'll guess it's my pc.
Problems with the collisions aren't too important, I've played the game a long time and I have been defeated many times, there's a option to change the dimension and I pressed that button, but I didn't notice that I was on another different dimension, is always the same dimension? I think you should change the color of the enemies when you change the dimension or something like this. I don't know if you are still working on this game, but if you have the chance to change it, I think, it would be good if you change something on the different dimensions.
By the way, the game is quite difficult though I like that ^^ besides I love that kind of graphics. The game concept is also pretty interesting.