# 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 + Bun fullstack server. Uses Bun as the package manager, runtime, bundler, and server.

## Commands

- `bun run dev` — start dev server with HMR (`bun --hot server.ts`)
- `bun run build` — typecheck (`tsc -b`)
- `bun run lint` — ESLint

## Architecture

**Server** — `server.ts` is the entry point using `Bun.serve()` with HTML imports. It serves the React app and API routes. The HTML file (`index.html`) is the client entrypoint — Bun's built-in bundler processes all referenced scripts/styles automatically.

**Auth** — Passkey (WebAuthn) authentication via `@simplewebauthn/server` + `@simplewebauthn/browser`. Server-side auth logic in `server/auth.ts`. Sessions stored in SQLite via HTTP-only cookies.

**Database** — SQLite via `bun:sql` (`server/db.ts`). Tables: `users`, `credentials` (passkey public keys), `sessions`. DB file: `leo-typing.db` (gitignored).

**Frontend Auth Gate** — `src/components/AuthGate.tsx` wraps the app. Shows login/register screen if not authenticated, otherwise renders the main app. Uses render-prop pattern to pass `user` and `onLogout` to `App`.

**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** — game selector with two games:
  - **Falling Words** — DOM-based falling words with combo system
  - **Missile Strike** — Canvas 2D missile flight game with interceptor dodging
- **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.

**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`, `playLaunch`, `playDodge`, `playMissileHit`, `playExplosion`.

**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.

**TypeScript config** — `tsconfig.app.json` covers `src/` (client code, DOM types), `tsconfig.server.json` covers `server.ts` + `server/` (Bun types).