Solid concept overall! Besides what was already said in other comments, it would be good to have clearer feedback (when your attack hits something, when you collect something, when you're hit and loose health, etc.)

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 ;-)

Was a bit hard distinguishing what’s wall and what’s background (floor). I would have gone for higher contrast colours. Other than that, fun game

I found the levels very disorientating, which I feel envokes the feeling of being lost, which fits the theme well. The music is nice. I feel the game could benefit from the character being locked to the tile map to give more of that gameboy feel :)