No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. Reviews and prices only.

Shadowgrounds

Shadowgrounds is an epic sci-fi game that blends addictive oldshool gameplay and modern technology into one big, nasty alien-slaughtering carnage fest. The game is played from a classic top-down perspective that gives you a better view of the battlefield and allows you to use your gear to its full potential. As you progress through the game, new tactics become available as your arsenal is upgraded with even more destructive tools of mass destruction. An impressive arsenal of upgradeable weapons allow you to kick alien ass in many different ways. One of the best alien-shooter games with epic boss fights and an interactive environment! Are you afraid of the dark? You should be, aliens in this game love dark places so use your flashlight wisely, the battery wont last forever!