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 $1.4M — a different platform, not this one.

Ziggurat

Dungeon-Crawling First Person Shooting at its finest! Fast-paced combat! Dozens of perks, spells and enemies! Level ups! Random Dungeons! Traps! Badass bosses! Carrots! Ziggurat is the best combination of First Person Shooter and Rogue-LITE you have ever seen. The game focuses on fast-paced first person shooting, with an old-school vibe, and updated handling and game mechanics. Dungeon crawling and RPG/Roguelike elements are added into the mix, resulting in a fun, challenging and varied game, with lots of content to discover. Get ready for your rite of passage: Enter the labyrinth and face dangerous challenges to prove your worth and become a powerful wizard! Smooth and quick First-Person-Shooting experience Plenty of equipment and perks to keep you entertained for ages! Skill-based dungeon crawling, with random generation and permadeath