Race Model

Each block is a slice of the race: set its distance and drag its pace — the split time for that block updates so you can pace by lap. Pick a preset distance or type a custom one (750 m, 11.2 km, …); ÷ carves a block in two (e.g. a 100 m sprint finish) and × removes one; the slider runs all the way to an all-out sprint. The D′ battery under the pace shows what's left at every point: faster than CV drains it, slower refills it. The optimal plan empties it right at the line; spend it too early and D′ empties before the finish (red) — forced down to CV for the rest, the blow-up you can see coming; leave some in the tank and you finished slower than you could.

Model it: hold the opening blocks at a pace and read “close the last … as fast as …” — the fastest you can run the final block before blowing up. Push an early block and watch that closing ceiling drop. Max the finish sets the last block to the ceiling. Ideal conditions only — no wind, terrain or altitude; this is a ceiling, not a guarantee.