zurbagan

The Zurbagan Shooter is a free, open-source FPS game. Its PC version is based on OGRE.
Protagonist and sidekick are hunters who notice advancing enemy troops in a narrow mountain pass. They send a messenger to the city of Zurbagan for reinforcements. Then they backtrack and create an avalanche. They build a barricade to halt the enemy advance. Once the enemy reaches the barricade, they shoot at soldiers.
The project involves students of Edinboro University of PA.