Really nice atmosphere and some great creature designs! My biggest recommendation is to work on the enemy pathing, waves of enemies just going straight towards the player work great for some genres, but for a bullet hell, it does not allow any form of dodging or attack pattern recognition. I also think the upgrade system could use some balance adjustments, it takes way too long until you have enough currency for the first upgrade. There are some solid bones of a game here, but I would recommend doing some continued playtesting and adjustments. Good work and keep at it!