Two sides, one battlefield
Natural Selection 2 is a team shooter where Frontiersman marines fight the Kharaa aliens across sci-fi maps. You play in first person: marines carry rifles, shotguns, grenade launchers and pistols, while alien players evolve into one of five lifeforms. The Skulk runs on walls and bites hard, the Lerk flies and spreads gas to support the team, the Gorge heals allies and builds tunnels, hydra turrets and walls, the Fade blinks in and out of combat with giant scythes, and the Onos is a huge, tough beast that squads struggle to bring down. Marines can also build Exosuits with miniguns and railguns, and use jetpacks for fast attacks on alien Hives.
Commander and squad play
Each team has a Commander who watches the battlefield from above instead of fighting directly. The Commander issues orders, places structures, gathers resources, researches technology and deploys abilities. A human Commander can drop health packs and ammo to a pinned marine squad or set up sentry guns for defence. An alien Commander can grow a new Hive to spread infestation into captured territory, which lets more alien eggs spawn. So a group splits naturally: one person runs the strategy layer while the rest fight on the ground, and the ground players' job is to hold territory so the Commander can build and expand. Cluster grenades clear ventilation shafts of hiding Skulks, flamethrowers burn alien structures and infestation, and Commander boosts make marines more effective in a fight.
Before you start
This is online PvP with a competitive, team-based focus, so a full group works best when you agree up front who will take the Commander role and how you will communicate with the ground players. Expect a mix of shooting and real-time strategy in the same match: holding a position matters as much as landing shots, and losing territory cuts off spawns and resources. The game is moddable — the developers ship the same tools they use, the code is open source, and mods can be published, shared and downloaded through the Steam Workshop, with mods downloading automatically when you join a modded game.