Shiden is a arcade style SHMUP (Shoot 'em up). Shiden takes influence from games like DoDonPachi, 超連射68k (Cho Ren Sha 68k) and Mars Matrix.
In these styles of game the player is a single ship that must face thousands of enemies and dodge all of their bullets whilst causing as much carnage as possible. While this may make you seem overpowered, your ship is actually noticeably weaker than most enemies, taking only a single shot to be destroyed. With a low entry barrier stemming from a simplistic control scheme, to a high skill ceiling for those interested in second loops, TFB and 1cc runs, SHMUP's are a genre of game that offer something for everyone.