Scrub through a fire progression — a time-ordered stack of perimeter snapshots — from either a saved Fire app run or a real incident's published mapping.
Pick a dataset, then drag the frame slider or press Play. The bright outline is the current perimeter; the faint trail behind it is where the fire has already been.
Found a progression of your own? Drop its .geojson file onto the map to add and scrub it — no need to edit any code first.
See README.md for the dataset format and where the real-world one comes from.