[livueta]

https://en.m.wikipedia.org/wiki/Cave_Story is one of the better-known examples.

> It was developed over five years by Japanese developer Daisuke "Pixel" Amaya in his free time.

[Kuraj]

And if you like this genre, Iconoclasts https://store.steampowered.com/app/393520/Iconoclasts/

[tubularhells]

Cave Sorry is a wonderful pearl of a game.