Firework Shockwave: The Sound Delay (3D)

A firework bursts at a real distance from you, in full 3D. The light flash reaches your eyes essentially instantly (light speed makes the travel time unmeasurable at these ranges), while the boom rides an expanding spherical wavefront that genuinely propagates outward at the real speed of sound — adjustable through air temperature and humidity via v = 331.3 + 0.606·T(°C), with a small humidity correction. Move the burst with the distance and altitude sliders, or click the ground to relocate and launch it instantly, then watch the live stopwatch and try to click "I heard it!" the moment the wavefront should arrive, comparing your guessed distance against the real one — the same trick used to estimate a storm's distance by counting seconds after a lightning flash.