Nixie — watch face for Wear OS

A nixie tube clock for round Wear OS watches (built for the OnePlus Watch 3, 466×466). Four IN-14 style tubes with glowing wire digits, the unlit cathode stack visible behind them, a hex mesh in front, and a neon battery gauge on the base.

The animation is rendered from the face's own layers.

Features

• Hours and minutes on four tubes, following the 12/24 h system setting
• Each digit glows at its own depth in the cathode stack, as a sheath of light around a darker metal core, and lights the cathodes, mica discs and rods next to it
• Hot core, orange halo and a faint violet haze that spills through the glass; the lit digit reflects in the curved walls and onto the base
• Tubes drawn as cylinders seen slightly from above: dark thick walls, a cage whose cells bunch up toward the sides, elliptical collars and discs, contact shadows
• Tilt parallax: the far cage, the near cage and the reflections on the glass slide against the digits as the wrist rolls (accelerometer), on both axes
• Tubes warm up each time the watch wakes: the glow spreads over the cathodes in patches, each tube at its own pace
• The outgoing digit ghosts for a second when the minute changes
• On the hour every cathode is lit in turn for 2.5 s, the anti-poisoning routine of real nixie clocks
• Tap the tubes to see the date (DD:MM) for three seconds
• Two bar-graph tubes on the base: battery and steps toward the daily goal
• Customisable: gunmetal, walnut or mahogany base; neon orange, deep red or amber glow
• No two tubes are alike: brightness, glass tone, dust and scratches differ per tube
• Neon colon bulbs
• Dimmed always-on (ambient) mode: digits only

How it is built

Pure Watch Face Format v2 — the APK contains resources only, no code. Every bitmap is rendered procedurally; there are no photos or stock art.

• tools/NixieRender.cs draws the tubes, digits and glow (System.Drawing with a custom blur/erode and layered additive glow). tools/render.ps1 compiles and runs it into res/drawable.
• tools/gen-xml.ps1 writes res/raw/watchface.xml — one image per digit per tube, switched by an alpha expression.
• tools/mock.ps1 composites a test frame locally, without a watch.
• build.ps1 builds the APK without Gradle (aapt2 → zipalign → apksigner, debug key).

.\tools\render.ps1              # regenerate bitmaps
.\tools\gen-xml.ps1             # regenerate watchface.xml
.\build.ps1                     # build\nixie.apk
.\build.ps1 -Install            # build + adb install on the connected watch

Requires PowerShell 7, the Android SDK (build-tools 37, platform android-34) and a JDK.

Install

Grab the APK from Releases and sideload it:

adb install nixie.apk

Then long-press the current watch face and pick Nixie. Needs Wear OS 4 or newer.

Font: Oswald, under the SIL Open Font License.