This mechanical math puzzle presents a diabolical challenge—you’ll need to spin each of the layered gears until every column radiating from the center adds up to 42 at the same time. Rated five out of five stars for difficulty, the wooden puzzle tests your visualization and problem-solving skills, whether you tackle it in one sitting or return to it over time. Designed with laser-cut wood, it makes a thoughtful gift for engineers, computer scientists, or anyone who enjoys a tough mental workout. The puzzle also doubles as a stylish display piece for a bookshelf or desk. Like all True Genius puzzles, this one draws inspiration from ancient civilizations and includes the backstory behind its design. It’s crafted by Project Genius, a U.S.-based, woman-owned company with over a decade of experience creating mechanical puzzles and strategy games. They also run a dedicated work program for young adults with autism.