Prodeus
Oh this is so much fun. These games are just so good! I’m just plucking another out the list, and then excited to ramble on about how much fun I had when I first played it.
Prodeus is a gloriously gory, faux-2.5D gibs of enemies exploding all over the place, in challenging levels that require you to piece together button presses and keys to find a route to their finish, mixing in verticality with ultraviolent combat.
There’s a sort of overworld, from which you select (or reselect) levels, and options to upgrade, and new abilities make revisiting older levels worthwhile, as inaccessible secrets enter your path. It’s a thoroughly modern take on a retro shooter, and one I keep returning to.
(Disclaimer: I have previously worked on games for Prodeus’ publisher, Humble, although never had anything to do with this game.)