Draw any closed outline and it meshes the interior into thousands of triangles, solves the Laplacian eigenvalue problem, and plays the real vibration modes that shape permits — finite-element math, not a synthesized approximation. Tap different spots on the drawn head and the mix changes, because each mode has its own nodal lines that stay still under your strike. It also ships Mark Kac’s two 1966 isospectral drums: different outlines, identical spectrum, indistinguishable by ear.