A radium dial watchface for Pebble — glowing tick marks, clean geometry, and a hidden clock.
Technical contributors and AI collaborators: Read
PROJECT_CONTEXT.mdbefore making any code changes. It contains the authoritative architecture, constants, platform table, build rules, and known traps for this project.
Old radium dial watches are beautiful objects. The hour and minute markings glow independently of the hands, giving you a sense of time without needing to parse a needle position. Radium 2 brings that idea to Pebble: the right half of the screen fills with minute ticks, the left half with hour blocks, a thin outer ring tracks battery and steps — and in the center, optionally, a clean digital readout.
The face works on two levels. With the overlay on, it reads like a normal watchface: time, date, day. Shake it, and the overlay disappears to reveal the full radial display — a pure starburst of glowing geometry that tells time in a completely different way. Shake again to bring it back.
- Radial time display — right half: 60 minute ticks in groups of 5. Left half: 12 hour blocks (or 24 in 24h mode, each block split in two)
- Overlay modes — Always On, Shake, 1 min auto-hide, or Always Off (pure art mode)
- 4 configurable info lines — Day, Date, Day+Date, Steps, Distance, Calories, Temp °F, Temp °C, Battery, Bluetooth status, Heart rate, Sunrise, Sunset, Daylight duration, or None
- Solar Ring mode — outer ring tracks daylight remaining and time until sunrise instead of steps and battery; stays alive on cached data if the phone disconnects
- Live weather — current conditions from Open-Meteo via phone, displayed with a custom icon
- Outer ring — battery level on the right, step count on the left, both filling from 6 o'clock toward 12
- Leading tick highlights — current hour and minute ticks glow brighter, independently colorable
- Charging indicator — battery icon swaps to a lightning bolt when on the charger
- Bluetooth alert — BT rune appears when phone connection is lost, with a double vibration
- Heart rate — live BPM on supported models
- 24h support — each hour slot splits into two segments with a gap between
- 17 independently configurable color slots
- 40 presets in five rows (Dark, Dark+, Light, Color, Special)
- B&W support with optional invert toggle
- All 7 platforms — Aplite, Basalt, Chalk, Diorite, Emery, Flint, Gabbro
12
███░░░░░░░░░
█ ░
█ WEDNESDAY ░
█ 10:42 ░
█ MAR 09 ░
█ ░
░░░████████
6
- Right half (3→12 o'clock): minutes, filling clockwise — each group of 5 ticks = one 5-minute block
- Left half (9→12 o'clock): hours, filling counter-clockwise — each block = 1 hour
- Outer ring right: battery, filling up from 6 toward 12
- Outer ring left: steps toward daily goal, filling up from 6 toward 12
- Center: configurable info lines and time, with optional overlay circle
| Mode | Behavior |
|---|---|
| Always On | Overlay always visible |
| Shake | Starts visible; shake toggles. Resets to visible on reboot |
| 1 min | Shake to show; auto-hides after 60 seconds |
| Always Off | Pure art mode — full starburst, no center hole |
| Platform | Watch | Screen |
|---|---|---|
| Aplite | Pebble Classic, Steel | 144×168 B&W |
| Basalt | Pebble Time | 144×168 color |
| Chalk | Pebble Time Round | 180×180 color |
| Diorite | Pebble 2 SE | 144×168 B&W |
| Emery | Pebble Time 2 | 200×228 color |
| Flint | Pebble 2 | 144×168 B&W |
| Gabbro | Pebble Round 2 | 260×260 color |
~2015 — Original design (Sterling Ely) The concept was designed for the Pebble Time Round: a radial bar graph where filled wedge segments encode time, battery, and steps — readable as pure geometry without a digital readout.
December 2015 — Prototype (MathewReiss) GitHub: MathewReiss/radium
December 2016 — v1.0 release (MicroByte)
March 2026 — Radium 2 (Sterling Ely and Claude) Full rebuild for all modern Pebble platforms. Adds color customization, 40 presets, 24h mode, 4 configurable info lines, live weather, solar ring, and health metrics.
- Rebble: https://apps.rebble.io/en_US/application/69a6531826cc4f0009c65926
- Repebble: https://apps.repebble.com/en_US/application/69a6531826cc4f0009c65926
Built with the Pebble SDK via CloudPebble. No external dependencies.
pebble build
pebble install --emulator basalt
Source files:
src/c/main.c— all drawing, event handling, settings, health, and weathersrc/pkjs/config.js— config page (data URL)src/pkjs/index.js— PebbleKit JS: platform detection, settings relay, weather and solar fetchpackage.json— message keys, target platforms, version
MIT