How are your reflexes? Ken Delahoussaye’s Pendulum Challenge (featured in MAKE Volume 26) is a fun and clever handheld game that you assemble on a printed circuit board. The game’s arc-shaped array of 15 LEDs (14 red and 1 green) simulate the path of a swinging pendulum, which you try to stop at the bottom of its arc through 5 levels of difficulty. A piezo buzzer adds sound effects (which the mode button can silence for the benefit of hard-working parents and studious siblings).