katsu

Katsu is a conjugation practice web app for Japanese verbs and adjectives.

The name is an abbreviation of the Japanese word 活用 (katsuyō), which means conjugation.

Conjugations can be practised for verbs, i-adjectives and na-adjectives.

The following forms can be practised:

• Formal or informal
• Past or non-past
• Positive or negative
• Te-form
• Volitional
• Tai-form
• Tari-form
• Potential
• Imperative / prohibitive
• Conditional
• Passive
• Causative
• Causative-passive

Demo

Use the app at katsu.arthurhoek.nl.

One app, two trainers

Katsu is growing a second trainer next to conjugation: kanji writing. The pattern for living together is one shell, sibling features:

• The shell (src/app) owns everything both trainers need: routing, the navigation menu, the home page, the options page, i18n bootstrapping, theme, settings persistence, service-worker updates and analytics. The cross-cutting services live in src/app/shared.
• A trainer is a lazily-loaded feature: its own routes file, pages, services and storage namespace, and its own translations installed when the feature is entered. Nothing of it lands in the initial bundle - that is the one boundary worth keeping.
• Sharing is the point, not the exception: features use the shell's services and components freely, and the shell reaches into a feature where that reads best (the options page shows the kanji pad switches next to everything else). Lazy loading already keeps the bundles apart; the code does not need to be kept apart as well.
• Settings split by reach: app-wide options (theme, language) belong to the shell's SettingsService, so a change made anywhere holds everywhere. Options only one trainer understands keep their own service (the kanji pad annotations, the conjugation forms), and the shared options page shows them all, grouped by reach.

The kanji feature already has the target shape. Conjugation is still interwoven with the shell (home, review and summary are its pages); the way to unify is to extract it into a sibling feature - conjugation.routes.ts, its pages moved out of the shell, SettingsService reduced to what is app-wide - and to do that the next time conjugation needs real work, not as a rewrite for its own sake.

Tech stack

• Angular 22 with standalone components
• Ionic 8 for the UI
• wanakana for kana input and conversion
• ngx-translate for i18n (English, Dutch)
• Installable as a PWA with offline support (Angular service worker)

Development

Requires Node.js 24 or newer (nvm use picks the right version).

git clone https://github.com/ahoek/katsu.git
cd katsu
npm install
npm start

The app is served at http://localhost:4200/.

Tests and lint

npm test    # unit tests (vitest)
npm run lint

Build and deployment

npm run build

The production build is written to dist/browser.

Every push to master is built and deployed to GitHub Pages automatically by the deploy workflow. The same workflow deploys the sync service for the kanji writing feature - a Cloudflare Worker configured in wrangler.toml - when the Cloudflare secrets are present. Its one-time setup is in src/kanji/README.md.

Acknowledgements

The word definitions were retrieved from the online dictionary Jisho.

License

MIT