Typed Japanese

Typed Japanese is a free, interactive course that teaches Japanese grammar by modeling every sentence as a TypeScript type. Each example is a self-contained snippet whose types prove it is grammatically well-formed. The built-in analyzer lets learners explore the structure particle by particle, making grammar tangible in a way that mirrors how programming tutorials introduce concepts. Designed for self-directed learners with zero prior Japanese, the course is written in natural English and Simplified Chinese. It assumes technical curiosity but no coding experience—the type system serves as a reasoning aid, not a prerequisite. The 47 chapters progress from elementary noun sentences through intermediate keigo to advanced literary patterns, always motivating each form by a real communicative need. What sets Typed Japanese apart is its dual audience appeal: traditional language learners get a structured, dependency-ordered path with every grammar point motivated before mechanics; programmers get a fresh metaphor where sentences are types that only compile if they are correct. The entire course runs in-browser, requires no signup, and is open source on GitHub. The project also extends the same idea to an English course—Typed English—though currently the focus remains on Japanese. All examples are interactive, and the type annotations provide instant feedback that conventional textbooks cannot replicate.