This is the best F2P game of all times. It's a 4 player co-op, 3rd person view, with RPG elements (leveling/gaining abilities). There are 4 distinct classes - Officer, Special Weapons, Medic, and Tech. Players can choose from 40 different pieces of equipment, ranging from weapons like assault rifles to grenade launchers and offhand items like mines and healing beacons. The game includes persistent statistics, unlockable equipment, and achievements. Team of marines is deployed in a colony which was invaded by an alien swarm, to search for survivors. It's not only about weapons, but using environment (exploding barrels etc.) and abilities like hacking, deploying mines etc. Co-op strategies and resource management are also needed, not just mindless shooting. I really don't remember having better time playing any other co-op game, free or payed.