The free, online multiplayer version of PC military shooter ArmA 2 has launched, mixing infantry combat with air, land, and sea assault.

Players of ArmA 2: Free can link up with those who have the full, paid-for version.

The difference is that ArmA 2: Free drops advanced graphics options, the story mode, and compatibility with paid-for expansion packs.

Player-made missions still work, and the game's armory of 300+ weapons remains accessible.

The release exemplifies a slightly different approach to that taken by Battlefield Play4Free, Global Agenda or AVA, which invite players to make in-game purchases.

Rather, it's similar in scope to F.E.A.R. Combat, which was F.E.A.R.'s multiplayer component released for free and compatible with the full game.

ArmA 3 is currently in development, expected Summer 2012.