Touhou Games are fun. Not just because cute girls doing cute things, but because they can actually be a lot of fun to play.
Anyway, Touhou, or "Project Shrine Maiden" is a "bullet hell" type of shmup developed by a single individual, ZUN. ZUN does all the graphic, coding, and music for the entire series. It all started with "Highly Responsive to Prayers" in 1996, then "Story of Eastern Wonderland" in 1997 followed by "Phantasmagoria of Dimensional Dream" and two more in 1998. All of the original games were played on the PC-98 system in Japan, though they were ported later on. It takes place in the fictional world of Gensokyo, which is basically like a romanticized rural Japan with magical elements. It's a realm separated from the rest of Japan for... reasons. And of course the main threat, the yokai, which are the non-human characters.
More recently, the games have been made for Windows, the latest being "Subterranean Animism" released last year. The next game, "Star-Lotus Ship of the East" is due to be released some time next month. There are so far 14 games, one released roughly once per year, including Perfect Cherry Blossom and Phantasmagoria of Flower View, both good ones. They're all more or less terribly addictive games with pretty patterns of death flying at you constantly. The screens full of bullet hell would be impossible to beat if not for the reasonably small hit box you have, so you can usually manage. Not to say it doesn't get... challenging at times, But that's the whole point. The difficulty levels of the games tends to vary a lot, too.
The amount of fan work surrounding the games is noteable. Lots of fan animations and artwork can be found.
Not to mention how much great music comes out of them. Also the number of remixes and fan works is... staggering. Which isn't necessarily a bad thing, either. Notably, "U.N. Owen was Her?", Flandre Scarlet's theme. Among dozens of others.
I may be inclined to spam some of said music here as well.