Matt Denton's Spoolbot looks almost exactly like a 2 kg spool of 3D-printer filament, complete with real filament wrapped around the outside. At a glance, there is little to suggest that it is a mobile robot.

Inside are an ESP32-C3-based controller, IMU, RC receiver, geared DC motors, and battery packs used as ballast. The spool's black end discs act as the wheels, while the internal frame stays upright as the shell rolls around it.