Zero-K Physics does the fighting

The fit for co-op friends is straightforward: the galaxy-spanning campaign supports co-op, so you can work through its 70+ missions and unlock technologies together. If you want something looser, survival mode drops your team against waves of chicken-monsters, while skirmish lets you and friends face non-cheating AI that plays fair. You pick factories, split metal and energy duties, and customize commanders with choices like cloaking or resurrection. You hold a ridge while your friend digs a canal behind it, then argue about who let the chickens through.

Terrain in Zero-K stays changed, which gives co-op games a shared building project. You crater fields to slow enemy tanks, dig canals to bring ships inland, and raise ramps, walls, and full fortresses. Hills block weapon fire, sight, and radar, so one player can hold high ground while another builds. Physics applies to units and projectiles too: nimble machines dodge slow shots, and gravity guns toss units across the map. You move a battleship onto a hilltop for longer range while your ally covers the climb.

Online play scales from 1v1 duels to huge team battles up to 16v16, plus free-for-all, ladders, replays, and spectators. The roster holds 100+ units with jumpjets, shields, teleports, EMP, napalm, and mind control, with no factions to learn. Control stays flexible: unlimited queues, painted formations, construction priorities, and orders for kiting and dodging. Matches stay fair because the game is really free with no paid advantages. You queue a thousand Fleas, paint them into a wide arc, and send spiders crawling up a cliff your tanks could never reach.