After 183 waterboardings, a terrorist’s mind can get a little fuzzy. The CIA found one way to keep Khalid Sheikh Mohammed sane and his information useful: letting him pursue hobbies in the hours that he wasn’t being harshly interrogated. So when the mastermind of the 9/11 attacks asked to be allowed to design a better vacuum, the agency said, why not? It’s not clear on just how far KSM got with his plans. According to the AP report, the prisoner, who has a degree in mechanical engineering, was entertained in other ways as well, including with Harry Potter novels, and homework on his al Qaeda knowledge, the completion of which earned him Snickers bars.