Half-Life 2 Mod - Lambda Wars v2.3.1

The Lambda Wars beta only requires Alien Swarm installed to play, but you must own HL2: Episode 2 on your Steam account. It features 3 multiplayer game modes: Sandbox, Annihilation and Overrun, showcasing the Rebels and Combine playable factions and a full-fledged RTS interface and HUD. There is also a singleplayer tutorial and a handful of singleplayer missions.