Concentric polyhedral shells — a tetrahedron inside a cube inside a dodecahedron — each free to rotate on its own axes. Connections between shells only exist where their vertices align, so rotating a shell rewires which paths a pulse can take outward from the core.
Activate the center and a pulse climbs the machine: the tetrahedron divides it into four phases, the cube recombines them into standing waves, the dodecahedron amplifies a single harmonic. The puzzle is solved when every outer vertex ignites in the same instant — planetary clockwork tuned like an instrument.
Full design notes live in puzzles/DESIGNS.md.