A good take on bullet-hell, but:
- Buff descriptions should be made a bit more detailed, so it's clear what you gain at the next upgrade levels
- It would be nice to add sound effects for different spells or for hitting enemies
- I'm not sure how the logic for subsequent buff drops is coded, but it could be set up so that upgrades for current buffs have a higher chance of appearing in the selection rather than entirely new ones
- Regarding balance: it seems to me that at this stage, it only makes sense to take buffs like books, ice, auras, etc., because other types of buffs don't provide much impact on the game