Stylistically, the game is consistent, which is good and I'm glad you were able to capture the "pen and paper" feel of the game. The audio was also well done and thematically appropriate.
Now, the issue I have is more with the genre itself conflicting with the game's visual choices. "Bullet Hell" style games are infamous for their fast pace and stunning visuals. Even on hard difficulty, the speed felt like it was going at a leisurely pace and I lost interest fairly quickly.
That being said, it's not bad, it just needs some tweaking if you're going for the intense move n shoot genre that I believe you intended.