Today's Alan Turing's birthday. He was a British mathematician and cryptographer who was instrumental in laying the foundations of modern computer science who tragically committed suicide after being persecuted for is homosexuality. But google has done a doodle in his honor—Turing machine puzzles! The bottom section is the set of instructions. The goal is to set them up such that when you press play the machine turns the number on the tape into the one pictured on the upper right. I think it's quite cool.