Splits
An offline-first race pace calculator for the start line.
2024 · Solo build.
TypeScriptPWA
The problem
Race pacing math on the start line is error-prone and stressful.
What it does
A tiny offline-first pace calculator with negative-split presets and shareable race cards.
Engineering decisions
Offline first, because start lines have no signal
Ten thousand people in one field means no usable network exactly when you need the tool. The whole app is a service worker and a few kilobytes of state, so it works in airplane mode and loads instantly on a cold phone in a start corral.
Presets over a blank calculator
Nobody wants to do arithmetic at 5 a.m. Starting from named strategies — even splits, negative split, positive fade — and letting people adjust from there matched how runners actually think about a race far better than an empty form with a target time field.
Where it landed
- Works fully offline, including first load from the home screen
- No account, no tracking, no backend to keep running