A danmaku (bullet hell) game series, produced by a single person for the last 20 years or so, that I’m currently playing a lot. So what is bullet hell? Well, here’s one image.
Yes, those are bullets, and you’re supposed to dodge them as you shoot to attack the boss.
The fact that I enjoy this game series immensely despite not liking shooting games in general might be because of my interest on difficult games. (Games whose genre includes “hell” in it should be hard…) And yes, I also like difficult games like Super Hexagon, oO, and such kind of games. (I also like puzzle games, but seeing that most puzzle games have no such difficult replayable sections, I like them for a different reason.)
How many of my little readerbase (if that’s a word) know this game?

