The 2D wave equation on a grid: each cell accelerates toward the mean of its neighbours, with light damping. Two point sources drive it.
Tap to add a source (up to 4). The same ?seed= always gives the same run.
LITThe discrete wave equation with Courant number below the stability limit. The field must stay finite (no CFL blow-up), or the page throws.
AMBEREdges absorb imperfectly, so some reflection remains.