What a great visualizer tool!
Observation: I never saw the link between Wave Equation Solvers, Finite Element Analysis (Eigenvalues, Eigenvectors, etc.) and Cymatics -- until I visited the above web page!
Related:
Cymatics: Chladni Plate - Sound, Vibration and Sand:
https://www.youtube.com/watch?v=tFAcYruShow
Cymatics: