Letter to Stars
Letter to Stars is an English diary and learning platform built by Mustafa Erhan Portakal, where a user writes a diary entry in English and Gemini rewrites it at a chosen IELTS level from 6 to 9. It also extracts the new vocabulary with Turkish meanings, and marks each day with a star on a visual progress map. It is live at lettertostars.mustafaerhanportakal.com.
What it does
A user writes a diary entry in English, and the platform returns the same entry rewritten at the IELTS level they are aiming for — 6, 7, 8 or 9. Alongside the rewrite it extracts the vocabulary that was new to that entry, with Turkish meanings. Each day of writing earns a star, which builds into a visual progress map over time.
The AI response is structured JSON rather than free text: the rewritten entry, grammar corrections, new words, writing tips, strengths and weaknesses, and overall feedback. Asking for a fixed shape means the interface can render each part in its own place, instead of showing the learner a wall of prose and hoping they find the correction inside it.
How it is built
The system is split across four services, each in the language that suited it:
- Frontend — React with Vite and Tailwind CSS.
- Backend — NestJS with Prisma over PostgreSQL.
- AI service — FastAPI, wrapping Google Gemini.
- Admin and analytics — Django.
Deployment is Docker Compose.
Where it stands
Letter to Stars is live at lettertostars.mustafaerhanportakal.com.