Contra is a freeware modification for Command and Conquer Generals: Zero Hour real-time strategy game. It's a big project started in 2004. It adds many new units as well as numerous new upgrades, new general's powers, buildings and new generals. It also adds new music and sounds, maps, bug fixes, enhanced graphics, and other effects, as well as three new Generals. There are tons of people playing in multiplayer. You can start a game at any time.
A new unit for Assault General. It's a vehicle for distant tunnel digging. Launches a rig which digs the ground and opens a tunnel. Requires Palace.