Firing a rocket-propelled grenade into a crowd of mutants and touching off a conflagration that engulfs a whole city block is all in a day’s work for the genetically upgraded police officers in Crackdown 2. The Xbox 360 game, out in July, mixes the open world of Grand Theft Auto with the weaponry and superhuman strength and agility of comic book characters. Result? Crashes, pileups, and explosions that would make Michael Bay envious. “This is an extremely physical game,” says Billy Thomson, lead designer of Crackdown 2, developed by Ruffian. “Everything is based on collisions.” But making the ultimate playground for mindless mayhem requires a great deal of math and code. Here’s where the processing power gets deployed.