Certamen practice machine

This summer, the big kids and I built a practice machine for the Junior Classical League's Certamen competition, based on an Arduino (clone) Mega 2560. It's a "practice machine" as it's not officially approved for tournament use (and perhaps can't be without the clicker shape being changed). Cost is about $80 (including filament), as compared to $400+ for the official version.

Build instructions are here. Code is here.