This is a full-stack typing practice web application (keybr.com) built as a large TypeScript monorepo. The system provides adaptive typing lessons that track every keystroke, compute per-key statistics, and automatically generate lessons targeting the user's weakest keys. It supports dozens of keyboard layouts (QWERTY, Dvorak, Colemak, regional layouts, ergonomic layouts) and languages, with phonetic model-based word generation for practice text. The application includes a multiplayer typing race mode via WebSocket, user accounts with OAuth authentication (Google, Microsoft, Facebook), premium subscriptions via Paddle, and a theme designer for custom UI themes. The architecture is a monolith with server-side rendering (Fastr framework), a React 19 frontend bundled with webpack, a MySQL/SQLite database via Knex/Objection, and a separate WebSocket game server. The codebase is highly modular with over 50 packages covering UI widgets, charts, keyboard layout definitions, binary serialization, color science, math/statistics, internationalization, and code syntax generation for code-typing practice. While primarily an application, it also contains significant data/research components: phonetic model generation from word frequency dictionaries, statistical analysis of typing performance (learning rate, speed distributions, polynomial regression), and a C++ tool for validating user data files. The repository demonstrates high craftsmanship with clean abstractions, extensive test coverage, and reusable libraries that could be extracted for other projects.