Black Mesa, the third-party Source Engine remake of Half-Life, is available to download now for free.

A PC-only release, the game has been worked on by a team of volunteers for over eight years.

It was due for release in 2009 but was delayed because the team were dissatisfied with the way it was shaping up.

The current version is missing Xen, the game's otherworldly denouement.

Valve itself ported Half-Life over to the Source engine with 2004's Half-Life: Source, although the original game’s textures and models were still used.

The game’s soundtrack may be purchased for any price the buyer specifies.