Calturin

This is classic hardcore bullet hell. 5 hours in game and I've finished all levels including increased difficulty. Would recomend to those, who enjoys hardcore gameplay and old school

It's fine but my biggest gripe about it is that every time you die its a sloooow fade into dark with a big "You Died" screen before glacially returning you to the middle of the hub instead of in front of the portal you failed at, making for a lot of unnecessary running back to the challenge.

Calturin is a fun little bullet hell boss rush game that can be pretty challenging, it has really good voice acting and the 8 unique bosses all have different patterns of fighting that makes them truly distinct from each other, there's also something called red and black portals which is basically a harder version of these bosses for people who want more of a challenge, it's also a good game to speedrun if you are into that and for its price you should definitely give it a try.