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 $213.3K — a different platform, not this one.

Shadowgrounds Survivor

Shadowgrounds Survivor is a next-generation adrenaline shooter and a spin-off/sequel to the underground PC hit Shadowgrounds. Shadowgrounds Survivor takes the battle against aliens to new epic heights. Join three battle-hardened survivors on Ganymede and fight back with a full arsenal of exciting weaponry and new tactics. Gear up and get ready! Three playable characters, each with impressive new tactics and weapons. An RPG-like upgrade system for weapons and characters including special attacks such as the all-engrossing Napalm Flame and the mighty Brute Slayer! Over 20 missions in the Campaign mode short of filler and full of action, running parallel to the Shadowgrounds story and expanding it to new locations, including snow and ice environments, gritty sewers, and the suffering New Atlantis colony. Survival mode where the player is pitted against hordes of alien monsters – the clock is ticking and they just keep on coming! Can you beat the highscores? Co-Op play for up to four players on the same computer.