type-review: Adaptive, Server‑Free Typing Trainer Open‑Sourced by Li Xiaolai

Introduction

type-review is a single‑page typing practice application open‑sourced by Li Xiaolai. It runs entirely in the browser, requires no registration, no server backend, and collects no telemetry, making it a privacy‑first tool.

Core Features

Adaptive letter unlocking based on per‑key statistics, confidence calculation, and over‑sampling of the weakest keys; new letters are unlocked only after the current set meets mastery criteria.

Benchmark mode that tests typing speed on real text, measuring word count and elapsed time to evaluate WPM, accuracy and stability.

Per‑key / per‑finger statistics panel showing WPM trends, finger‑speed breakdown, error breakdown, daily streaks and milestone tracking.

Optional visual keyboard that colors keys by mastery, shows real‑time press state, and supports Mac/Windows layouts as well as QWERTY, Colemak and Dvorak keymaps.

Optional keyboard sound packs (mechvibe synthesis, soft packs, real‑sampled typewriter sounds) generated locally with Web Audio.

Shareable result cards via a link #/share/<payload> that display read‑only results without exposing full history.

Technical Architecture

The lightweight stack consists of SolidJS, strict TypeScript, Vite, Vitest + jsdom, Biome and pnpm, with only solid‑js as a runtime dependency.

Architecture is split into three layers:

UI – built with SolidJS.

IO – DOM, IndexedDB and Web Audio adapters.

Engine – pure TypeScript.

Purity rules enforced by src/layer-purity.test.ts prevent the engine from importing IO or UI and IO from importing UI.

Key Design for Low Latency

keydown
  → InputHandler.handleKeyDown
  → Session.input
  → requestAnimationFrame
  → setSnapshot
  → UI partial update

Key events directly modify the Session state in a plain TypeScript class, avoiding reactive tracking of every 60 Hz keyboard event and ensuring a short, deterministic path.

Privacy and Security

No analytics, telemetry, cookies or third‑party fonts.

User data stored in IndexedDB with JSON export and one‑click clear.

Strict security headers: CSP default‑src 'none', frame‑ancestors 'none', COOP/COEP, disabled permissions (camera, microphone, geolocation, payment, USB), X‑Frame‑Options DENY, X‑Content‑Type‑Options nosniff, Referrer‑Policy no‑referrer.

Quick Start

Run locally:

git clone https://github.com/xiaolai/type-review.git
cd type-review
pnpm install
pnpm dev

Access the app at http://localhost:5173.

Docker image:

docker run --rm -it -p 80:80 registry.cn-beijing.aliyuncs.com/opencontainers/type-review:latest