MOD OF THE WEEK In Mod of the Week, Chris Livingston scours the world of user-created adventure for worthy downloads. This week, a mod that turns one of the best shooters ever into an RTS.

Lambda Wars (originally HL2 Wars), a real-time strategy set in the Half-Life 2 universe, is a mod years in the making and has now had an official launch on Steam. This mod of Alien Swarm provides a bird's-eye view of the struggle between the Combine and rebels and includes both single-player and online play. The world of Half-Life 2 is perfect for a translation into classic RTS play, and the mod is both free and now completely standalone, so there's no reason not to give it a try.

If you haven't played any of the mods earlier incarnations, there's a decent little tutorial to help you get started. You begin with a little base-building. Recruit an engineer from your headquarters, and you'll be able to construct a barracks (which lets you generate rebel soldiers, everything from simple citizens with guns to harder-core veteran grunts, and specialized units like medics and fleet-footed scouts). Build a munitions plant and you'll be able to upgrade your soldier's weaponry, unlocking frag grenades, shotguns, and rifles. There are some nice little animations as the buildings are completed, sort of like the intro to Game of Thrones but with rusty little shacks instead of medieval cities.

You can also play as the Combine, who have counterpart units. Their HQ is a tiny little citadel (so cute!) and their engineers are stalkers, those weird, gaunt former humans who shamble around projecting laser eye-beams. You can build city scanners (those flash-photo taking hovering bots) to scout the map, auto-turrets, various Combine soldiers, hunters, and even striders.

The sound effects are also straight out of Half-Life 2, and goes a long way to making it feel authentic (when you order your rebel soldiers around, they call you Doctor Freeman). Combat, despite it being an RTS instead of an FPS, still has many of the same elements. For example, shoot a zombie and its headcrab will pop off and leap after you. I also had two Combine turrets wipe out an entire group of my rebel soldiers before I realized, oh yeah, in Half-Life 2 you need to lob grenades at them to knock them down. Same thing here.

Multiplayer supports up to eight different teams, and if you're short a few friends the AI can fill in. There are a few different game modes, including one called overrun, which brings in wave after wave of antlions for you to fight off while constructing defenses as fast as you can. Single-player has a number of campaign missions as well.

Online matches, at the moment, are a little hard to come by: there's a lot of waiting for lobbies to fill, only to have everyone ready to play except for one person, who then leaves, and then everyone else starts leaving to find other lobbies. Hopefully more people will be checking this game out in the days ahead, but in the meantime I found single-player enjoyable enough. You can grab it on Steam here.