Kinda annoying that this is being called a "retro" shooter when the only retro thing about it is the graphics. This isn't like any other game I've played before, and it's amazing. Hard as nails (definitely worth playing on the "violent" difficulty), and extremely satisfying, with a very high skill ceiling. Actually for that matter, the skill floor is awfully high as well. There are two bosses in this that will annihilate you within seconds if you don't do everything exactly right. Certainly helps that there aren't any loading screens upon death, you just tap "R" and jump right back in, with the only consequence being a restart penalty on your score. It's demanding, but so worth it. Amazing fun, very easy to recommend.