Zero-K is a FREE, multi-platform, open source Real Time Strategy game, which aims to be a dynamic, action-packed, hassle-free experience, full of clever strategies and constantly moving combat. Includes an epic scale, realistic projectile and unit physics, terraforming terrain and hundreds of unique and interesting units.
High quality production for a mod but gameplay sucks. Too many different factories and no way to scout which will be build by the enemy. Also gameplay is focused on 1 factory only (sometimes 2) which limits tactical/strategical gameplay. Also the community is quite unfriendly.