# CLAUDE.md

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

## What This Is

A typing tutor app for a child (Leo), built with React 19 + TypeScript + Vite. Uses Bun as the package manager/runtime.

## Commands

- `bun run dev` — start dev server
- `bun run build` — typecheck (`tsc -b`) then build for production
- `bun run lint` — ESLint
- `bun run preview` — serve production build locally

## Architecture

**Modes** — The app has four tabs, each a top-level component rendered by `App.tsx`:
- **LessonMode** — structured lessons with progressive key introduction; lessons unlock sequentially (90%+ accuracy required)
- **FreeMode** — free typing practice using random quotes
- **GameMode** — arcade-style falling-words game with combo system and sound effects
- **StatsView** — charts (recharts) showing WPM/accuracy trends and per-key heatmaps

**Core hook: `useTypingEngine`** — shared typing logic used by LessonMode and FreeMode. Tracks cursor position, errors, WPM (updated every 500ms), per-key hit/miss stats, and fires `onComplete` when text is finished. GameMode has its own input handling since its mechanics differ (falling words, not linear text).

**State: `useStats`** — persists `UserProgress` (completed lessons, session history, game high score) to localStorage under key `leo-typing-progress`.

**Sound: `sounds.ts`** — all audio is synthesized via Web Audio API oscillators (no audio files). Exports: `playKeyClick`, `playWordComplete`, `playCombo`, `playMiss`, `playGameOver`.

**Data files** — `src/data/lessons.ts` (lesson definitions with word lists), `src/data/quotes.ts` (free mode texts), `src/data/keyboard.ts` (key-to-finger mapping for the visual keyboard).

**Styling** — CSS Modules (`src/styles/*.module.css`) plus a global stylesheet.