Mega City One isn't quite Half-Life 3, but it is a three hour-long single-player campaign which plants you in the shoes of Gordon Freeman and sets you off on an alternate timeline in a bid to save the world. Its version 1.0 is out now.

Inspired by an unorthodox combination of the movie Dredd, and games Tomb Raider and Resident Evil, Mega City One sees Freeman again siding with the Rebels against the Combine this time in search of a lost Xen crystal. The next phase of your adversaries' invasion of earth is hinged on acquiring the ancient artefact thus you'll visit ancient ruins, old temples, villages, mansions, and ultimately the city in your quest to get there first.

"All difficulty levels have been completely rebalanced compared to the main game, to make the experience more challenging and fun at the same time," explains mod creator Abdulhamid Cayirli, who goes by the pseudonym Crowbar. "On the hardest difficulty it is essential to explore and conserve ammo. The difficulty levels have also been smoothed out and the levels are all designed for every difficulty level."

Mega City One came to be when Crowbar entered RunThinkShootLive's mapping tournament 'The Hammer Cup' last year, designing various maps for the competition's five challenges. Following the event, Crowbar decided to rework his designs, remake areas, and implement the feedback he received from the tournament's players. He's since added entirely new maps in order to fill the gaps.

"The great thing about this is that all maps have been extensively play tested, so you can expect a very polished experience in terms of gameplay," says Crowbar.

Mega City One's version 1.0 is out now—head over to ModDB for download links and installation instructions.