Source Forts
Game mod of: Half-Life 2

Background

Sourceforts is a multiplayer mod for Half-Life 2 in which you build forts to protect your flag and fight in teams. You have a limited time to build using physics objects lying around the map.

Once the time is over, the battle starts, you must capture the other team's flag and bring it back to yours. After the battle time runs out, you go back and rebuild your fort.