The idea, theme and art of the game is great! However, it is not playable (yet)... no music or sound effects, clippping errors, dead enemies having a spasm, unfinished animations or coding, it is too difficult etc. 

The programmer is a hero for making it this far with pure Java... it is borderline insanity at it's finest tbh (I don't think I could do that in a week and I'm not that bad a programmer), but I think if you would have used any engine at all, you would have saved a lot of time and I probably would not have anything to criticise at all...

Among all submissions to 2D games jam, that's one I loved the most. I can see you reealy made a good effort to make this. Good luck!