No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. The Steam version is estimated at $42.2K — a different platform, not this one.

Footgun: Underground

Roguelike with balls! Prove your ball skills and dribble your way through a randomly generated, dangerous track network full of deadly challenges! Face post-apocalyptic mutants, improve your balls with high-tech upgrades and escape the pixel art underground labyrinth.     You wake up sometime in the future in a cryo capsule. You don't know who you are, but one thing is clear: You have a cybernetic leg, a ball and enemies to fight! Master your new weapon, explore this strange underground world and try to escape this post-apocalyptic madness.      Footgun: Underground has a very special challenge: Instead of guns, magic or swords you have only one weapon to master: your futuristic ball of death. In classic Roguelike fashion, you explore random rooms, fight different creatures and upgrade your equipment along the way. Death is part of your journey, so don't give up, learn the ball control and the synergies to successfully move forward through the dark depths of the underground. But beware, not all enemies are your normal grubs...    Just kicking the ball and hitting the enemies on the ground is pretty easy, but the true challenge lies in the precise control of your mighty weapon. Leverage the angles and layout of the rooms as well as the behavior of the different enemy types to create a barrage of violence. With a variety of different, unlockable characters as well as a multitude of unique balls, each run you will find many builds and different playstyles to experiment with. Features Multiple characters and balls  Glorious Pixel-Art  Motivating upgrade system through stackable chips  Variety of biotopes with unique enemies and bosses  Piñatas?!