Tremulous

Tremulous combines first-person shooting with real-time strategy, creating a multiplayer battlefield where humans and aliens fight for control while also constructing structures and developing their forces. Players do not simply run around shooting everything that moves; teams must gather resources, build bases, choose upgrades, and coordinate their attacks. The two sides play quite differently, with humans relying on firearms and technology while aliens evolve and use very different movement and combat abilities. This combination gives matches a tactical layer rarely found in conventional shooters. Bases can grow into elaborate defensive positions, although a determined enemy can eventually turn all that careful construction into modern art. Tremulous remains an interesting example of how community-developed games experimented with mixing genres long before such combinations became commonplace.