A watt is a fact; a zone is what it costs you. The biggest number on the
ride screen was the same shade of white at 90 W and at 400 W, which is a
thing no training app has done in fifteen years.
Zones, with two rules:
- **No reference, no zone.** An unset FTP draws the plain number. A zone
measured against a guessed threshold would paint every ride with a
confident lie.
- **Colour never carries it alone.** "Z4" renders beside the swatch, so
the meaning survives a colour-blind rider, a phone in direct sun and a
black-and-white screenshot.
Read off the rolling average, not the instantaneous watts: at 4 Hz the
raw figure crosses two boundaries every pedal stroke, and a colour that
strobes is worse than no colour. Not pedalling is not zone 1.
Units are a display preference applied at the last step before the
glass. Everything computed, stored and recorded stays SI, so a FIT file
never depends on what the screen was set to. `format.ts` takes the unit
system as an argument rather than reading a module-level setting — pure
functions are what let every readout redraw the moment it changes. The
`km` helper is gone rather than left beside `dist`, so there is no
second way to format a distance that ignores the preference.
Rust's block labels lose their baked-in kilometres. The block already
carries start_x and end_x and the frontend renders that span in the
rider's units; a kilometre in the text sat inside a sentence saying
miles everywhere else.
Also on the ride screen:
- The gradient gets a wedge beside the number. A signed decimal has to
be read; a slope is seen. Exaggerated and clamped, because a true-scale
6% is indistinguishable from 3% at 40 px wide.
- What is coming, from the profile's own block list — "2.1 km at 12% in
460 m". The chart says where the rider is; what is about to happen is
what decides whether to shift now. The data was already computed
Rust-side and thrown away here. Close in, the small unit reads better
than a fraction of the big one.
- Mode and target merge into one chip. They are a single fact, and
splitting them spent a chip of header width repeating the word
"target".
- The pod chip no longer reports a missing `+` pod while the `−` pod is
connected. The `−` pod relays its twin, so that is the intended
configuration — the ride screen was calling it a fault, contradicting
the device screen two keystrokes away.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dtourolleandClaude Opus 5
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