Sign up to receive each week’s Playlist e-mail here! Also check out our full, interactive Playlist section. Perchang (iOS) BY PERCHANG LIMITED The over-engineered contraptions of Perchang do look a lot like Rube Goldberg machines but they differ very slightly. That difference is that they aren’t strictly there for you to look at; you must also operate them. The goal is simple each time: ensure a pre-requisite number of tiny balls enter the hole before the timer finishes. Without your interaction, this won’t happen, and so you have to press your thumbs on the screen to activate fans, or flippers, or tilt a…