Alpy — free ski app
The Day, Written: a coach’s debrief from your own numbers
The end of a ski day produces a pile of numbers. Most apps show you the pile. Alpy also reads it to you — a short paragraph in the voice of a coach going over the data, built from athletic measures that actually say something:
- Descent rate — vertical meters per hour of descending, the cleanest “how hard did I ski” number there is.
- Time on snow — how much of your mountain day was actually spent descending (“41 min descending across a 3 h 12 m day” is a very normal, very clarifying ratio).
- The standout run — your fastest average descent, with its drop, time and speed.
- Records — personal bests on named runs, with the margin you beat them by.
- Consistency — how tightly your per-run top speeds grouped.
- Conditioning — whether your turn cadence held, rose, or faded across the day.
- Load — airtime and peak turn G from the accelerometer, always labeled as the estimates they are.
The one rule: never invent
The paragraph is written by Apple’s on-device model when your iPhone has one, and by a deterministic template when it doesn’t — the card labels which voice you’re reading. Both voices live under the same contract: use only the measured facts provided; never invent conditions, snow, places, feelings, or numbers. Facts your day didn’t produce are omitted entirely rather than padded around. If you set no records, the word doesn’t appear.
This matters because AI summaries drift toward flattery and filler. Ours can’t: the prompt hands the model a fixed set of measured sentences and the job of making them read well — a rephraser, not an author. When the model isn’t available, the template assembles the same facts in the same register, so the debrief never silently changes meaning with the hardware.
Why “athletic” framing
Early versions of this feature read like a diary — pleasant, forgettable. The rewrite treats your day the way a coach treats a training log: work done first, quality second, trend third. Skiing is a sport; your data deserves the sport’s vocabulary.
And because everything is computed on the phone from your own GPS and motion sensors, the debrief arrives with the same privacy as the rest of Alpy: no account, no server, nothing uploaded.
The Day, Written sits at the top of every Ski Debrief. For what the rest of the debrief holds — per-run registers, lift lines, records — start with a first day with Alpy.