The UCS is a 25-square block replica of downtown Seattle. The entire complex is studded with sensors and remote cameras linked to a large computer in a bunker in the center of the simulation. Companies of soldiers in full combat armor enter the simulator to confront a variety of simulated opponents. Soldiers and their opponents use simislugs, bullets that mimic the trajectory and speed of normal rounds, but that melt on impact with and solid object. Even with simuslugs, simulator runs are dangerous in the extreme, especially for members of the Metroplex Guards Special Forces who dutifully risk their lives to provide the soldiers with live targets.