Rigid rods that never touch, suspended inside a web of tensioned strings. Tighten or slacken a string, move an anchor, hang a weight — and two mathematical systems answer at once: the force balance that keeps the structure aloft, and the vibration modes that make it sing when plucked.
The trap is that the systems disagree. A configuration can stand proudly and sound like a dropped toolbox; another can hold a perfect chord for one heartbeat before folding. The solution must satisfy both — alien engineering where the certificate of structural integrity is a musical note.
Full design notes live in puzzles/DESIGNS.md.