Nice one, it got me hooked up till the end. I only defeated the boss due to a bug; I could continue attacking even though I was supposed to be dead. Otherwise it would have been impossible, it shoots from all directions when attacked, meaning instant death. Unless the damage done to it is cumulative with each... passing. One more thing, are the holes on the floor supposed to hurt you?
Mouse control is not part of gameboy experience; you should remap to a keyboard key ;-)