# CALCULATOR — round-screen calculator for Xiaomi Watch S4

A calculator laid out for the circular display: tapered key rows that follow the
chord of the round screen, large touch targets, high-contrast keys (#3a3a3e on #000).
Supports chained operations, percent, sign toggle, decimals, and divide-by-zero
error recovery.

**Status: WORKING ON WATCH** (user-confirmed through v1.2; layout improved through 1.6).

## Usage

- Tap keys to compute; `AC` clears all
- `%` divides the display by 100 (plain semantics — 200+10% = 200.1)
- Back button exits (no onBackPress interception — intercepted back made the
  button feel dead on a single-page app)
- Crown does nothing (unsupported API on Vela); the original crown-selection
  scheme was abandoned for a directly-tappable list layout

## Round-screen layout (the interesting part)

- Short viewport (~300px) so rows never exceed the circle chord
- NO vertical margins on list-items (spacing baked into height — CSS/JS drift bug)
- Top/bottom spacer items so first/last keys can center in the viewport
- Focus = round((scrollY + KEYS_H/2 − ITEM_H/2 − PAD)/ITEM_H); re-centered after
  every press via scrollTo
- Geometry + contrast assertions live in `tests/visual.cjs` (parses the .ux)

## Project layout

```text
src/
├── app.ux, manifest.json   # com.example.hellovela identity (preserved for updates)
├── common/icon.png         # 192×192 circular icon
└── pages/index/index.ux    # keys list + display + state machine
tests/
├── page.cjs                # state machine: driven via press(key) sequences
└── visual.cjs              # parsed-from-source geometry/contrast contracts
```

## Build & test

```bash
npm ci
npm run release
node tests/page.cjs
node tests/visual.cjs
```

## Install

Side-load via AstroBox. Releases:
https://gitea.oimcloud.myaddr.tools/codex-bot/vela-calculator

## Bug history worth knowing (all caught by the stale-test TDD pass)

- `fresh` never initialized → first digit appended to '0' ('01')
- `=` with no pending op zeroed the display
- Operators didn't auto-evaluate pending ops (2+3×4 gave 12, not 20)
- Repeated `=` didn't re-apply the last op (2+3== gave 5, not 11)