# Nexus Calculator POC — Evidence

POC 1.0 for the first-party Nexus Calculator in Ninja Nexus Shell (not Windows Calculator).

## Scope

- 420×620 centered glass window with Nexus cyan/purple styling
- Standard mode: digits, `+ − × ÷`, `%`, `.`, `=`, `C`, `CE`, backspace, `±`
- Keyboard: numbers, operators, Enter=`=`, Esc=`C`, Backspace=delete
- Launcher wiring via `nexus:calculator` (`app-calc` in `apps.manifest.json`)
- Lockdown blocks `calc.exe` with message: **Åbn Nexus Calculator i stedet.**

## Architecture

| Layer | Type |
|-------|------|
| `NexusCalculatorView` | WPF UserControl |
| `NexusCalculatorViewModel` | MVVM binding |
| `NexusCalculatorService` | Orchestration |
| `NexusCalculatorEngine` | Pure logic (unit tested) |

## Screenshot checklist

Capture from a Release build with `--safe-poc` or `--overlay`:

- [ ] `calculator-open.png` — Nexus Calculator window on desktop (title + Standard Mode + display)
- [ ] `calculator-operation.png` — Visible expression line and result after an operation (e.g. `10 ÷ 2 =` → `5`)

Store screenshots in this folder next to this README.

## Manual verification

1. Launcher → **Nexus Calculator** (pinned app-calc)
2. Click `1 + 1 =` → display `2`
3. Press Esc → display resets to `0`
4. Type `10 / 2` and Enter → display `5`
5. With lockdown active, attempt Windows Calculator → blocked message suggests Nexus Calculator

## Automated tests

```powershell
dotnet test "source/nexus-shell/NexusShell.Tests/NexusShell.Tests.csproj" -c Release
```

Covers: `1+1`, `10/2`, `5*5`, `10-3`, percentage, decimal, clear, backspace, division by zero.

## POC-only limitations

- Standard mode only (no scientific / programmer / history)
- Single-window instance; no dock tile yet
- No Nexus Console command (`calculator-test`) in this POC
- Percent uses simple `/100` or `% of accumulator` when operator pending
