Calculate velocity; explain the Maltese cross mechanism that’s the basis of the motion picture projector; and work out the ways different pendulums (including Foucault’s famous version) swing. Every attractive page in master Ivan Moscovich’s eleventh collection of brain-busters offers a tricky puzzle pleasure. Sixteen tiles show either a crowned frog or a crown prince: distribute them randomly on a game board, face down, and then see if you can come up with a  configuration that will allow you to flip them so that all frogs or all princes will turn up. Discern the logic of a number pattern in a partially filled-out grid and discover the missing numerals. From gnomic expansions to infinity and limit, these dilemmas demand a smart solver.