Are you sitting down? If not, you should sit down. Okay, are you sitting down now? Because you should probably actually be lying down for this: As of right this moment, we are giving all current owners of Portal 2 a 75% off Portal 2 coupon. If you're standing back up, dusting yourself off and wondering why you'd want another copy of a game you already own, lie back down real quick because here's the lie-down part: We just added co-op to the Perpetual Testing Initiative.