Instrument 4 of 8
The Rose Engine
The lathe ornament of banknotes and certificates: one circle rolling inside another, the pen offset from center. Coprime radii close the curve after many turns.
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How it works
Module: Guilloche — one file, zero dependencies beyond three.js, reused verbatim by this site's own ornament. Parameters are announced to screen readers through aria-valuetext; the whole instrument is operable from the keyboard.