# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

Interactive web application that visualizes how percentage-based salary increases amplify absolute salary differences over time. Norwegian-language UI ("Lønnsforskjellen vokser" = "The salary gap grows").

## Architecture

Hosted at `forskjeller.naiv.no`. Static site in `public/` — no build system, no package manager. Serve `public/` as the site root. Each topic gets its own subdirectory (e.g. `public/lonn/`).

- `public/lonn/index.html` — Page structure: header, 4 range-slider controls, 4 stat cards, 4 chart canvases, explainer section
- `public/lonn/style.css` — CSS custom properties in `:root`, CSS Grid layouts, responsive breakpoints at 560px/480px/360px
- `public/lonn/app.js` — All logic:
  - `fmtKr(n)` / `fmtShort(n)` — Norwegian locale number formatting (nb-NO)
  - `getData()` — Computes compound growth arrays from slider values
  - `baseOpts()` — Shared Chart.js config factory for all 4 charts
  - `update()` — Reads sliders, recalculates, updates DOM and charts (called on every `input` event)

**External dependencies** (loaded via CDN, no install needed): Chart.js 4.4.1, Google Fonts (Fraunces + DM Sans).

### Key Design Decisions

- All 4 charts share `baseOpts()` — modify this for consistent chart styling changes
- Charts update with `'none'` animation mode for responsive slider interaction
- Mathematical model: gap = `(B₀ − A₀) × (1 + r)ⁿ`

## Development

```bash
python3 -m http.server 8000 -d public
# open http://localhost:8000/lonn/
```

## Language

All user-facing text is in Norwegian Bokmål (nb-NO). Use Norwegian for UI strings and `nb-NO` locale for number formatting.