The direct successor to the Rubik's Cube: twenty-seven cells, each holding a resonator oriented along one of three axes. The layers rotate exactly as you expect — but instead of matching colors, you are routing waves. Energy pulsed into the cube must travel closed loops and return; a solved cube leaks nothing from its surface, and opposite faces oscillate in matching phase.
Unlike a maze, routes overlap: waves cross the same cell on different axes without touching. A fully solved cube carries several simultaneous resonant circuits — one around each axis and a diagonal mode threading them together — which makes the design space enormous, and is exactly why it needs its own dedicated build.
Full design notes live in puzzles/DESIGNS.md.