Red Sky is an FPS game with the same kind of old-school gameplay from the mid-90's, with 16 tough levels and lots of varied gameplay. The game takes at least two hours to beat, but many more if you aren't an experienced player, and is running on its own custom 3-D engine.

Over the land of VOID-LAND, a land on the edge of an endless void, an evil from beyond the abyss takes control over key facilities with its evil minions, who teleport into these facilities with special warp gates. Its up to you to fight your way though every single facility which has fallen, and follow the trail of warp gates back to the source; defeating the army of possessed humans and killer cyborg-minions that threaten to take over void-land! The sky goes red from the horrible death-signals, but luckily you were smart enough to buy a water filter... I bet they aren't laughing now! You grab your combat rifle- the only thing between you and the alien death squads-- go forth, and make your LAST STAND against the minions!