Hop into your favorite favorite time machine and rewind to 2002. Half-Life's modding scene roars with creative energy, and the community raves about the latest homebrewed handiwork: Natural Selection. From the start, it had the mark of a mod with staying power. The brainchild of creator Charlie "Flayra" Cleveland and a tribute to science fiction horror staples such as Alien, Natural Selection combined strategy, first-person shooter action, and good old piss-your-pants fear.

The setup is simple: A team of Marine players pits their weaponry and fancy gadgets against another team -- the alien Kharaa. The latter boasts mobility, the ability to evolve into stronger forms, and really sharp teeth. The former features the "Commander" position, providing a single Marine a bird's-eye view of the map along with the capability to issue upgrade purchases, construction and movement orders, and supply drops. The result is a frenetic scramble for precious resources zipped up in a twitch-based shooter's shell.

When more accessible eye-candy generators -- Valve's Source, Crysis' Crytek Engine, and Doom 3's id Tech for example -- rode into town over the passing years, Natural Selection naturally geared up for its next incarnation. Flayra (now helming startup developer Unknown Worlds Entertainment) could've chosen a powerful, pre-existing engine. Instead, Unknown Worlds reinforced modding's total awesomeness by switching to a custom game engine built from scratch.

Check out Natural Selection 2's latest progress video below, and be sure to head over to the project's official website for more info.