Introduce Kletka - chess analyzer

🌐 https://andreykhrypach.github.io/Kletka/

The idea is simple: allow working with PGN, analyzing positions with Stockfish and — most importantly — exporting the variation tree directly into a Polyglot book.
Previously, working with Polyglot books required separate utilities and the command line. Kletka brings everything together in one place: analysis, PGN work, book editing and exporting the variation tree into .bin.

## What Kletka can do:

- Open, edit and save PGN files
- Full support for variations and annotations
- **Loading, viewing and editing Polyglot books right inside the app**
- **Exporting the analysis tree into a Polyglot book** — creating your personal repertoire
- Position analysis with the Stockfish engine
- Copying a position as FEN + ASCII (Ctrl+Shift+P)
- Multilingual: Russian, English, Chinese
- Customizable board themes

## Coach tools:

Kletka was created not only as an analyzer, but also as a tool for those who teach chess — coaches, parents, mentors.
**What you can do directly on the board:**
- **Draw arrows** — show plans, diagonals, key lines, weak squares.
- **Place crosses** — mark mistakes, weak squares, dangerous squares.
- **4 marker colors** — blue, red, green, black — for different types of notes.
- **Circle on a square** — to highlight a specific square.
- **Undo / Redo** (Ctrl+Z / Ctrl+Y) — instant undo and redo of the last marker.
- **Auto-clear** when changing position or flipping the board — markers don't «stick» to old squares.

**Why it's useful:**

- Reviewing a game with a student — show mistakes and correct continuations.
- Explaining opening ideas — draw a piece development plan.
- Endgame analysis — mark key squares and diagonals.
- Tournament preparation — visually capture typical mistakes.
All markers work **on top of the board** — you can draw and **analyze at the same time**. Arrows and crosses **don't interfere** with working with pieces.

## How to install:

**Windows**: download the `.exe` from the releases page - https://github.com/AndreyKhrypach/Kletka/releases and run the installer.
**macOS**: download the `.dmg` from the releases page - https://github.com/AndreyKhrypach/Kletka/releases - open it and drag `Kletka.app` into the `Applications` folder.
**Linux (Debian/Ubuntu)**: download the `.deb` package from the releases page - https://github.com/AndreyKhrypach/Kletka/releases and install it via `sudo dpkg -i kletka*.deb`.

## After installation
Open Kletka, load a PGN file or set up a position, connect Stockfish (Engine → Configure Engine) and start analyzing.
If you'd like to try the Polyglot export — analyze a game with variations, then go to Books → Export to Polyglot book. The resulting `.bin` can be used in Stockfish, Leela, ChessBase, Scid, Arena.

## Feedback
Kletka is an open-source project (GPL v3). If you try it — share your thoughts here on Lichess.

## Links
- 🌐 **Website:** https://andreykhrypach.github.io/Kletka/
- 📦 **Download (all platforms):** https://github.com/AndreyKhrypach/Kletka/releases
- 💻 **Source code:** https://github.com/AndreyKhrypach/Kletka
- 📺 **Video tutorials:**

• Windows installation - https://www.youtube.com/watch?v=OSaSA-Qm0GY
• Setting up Stockfish on Windows - https://www.youtube.com/watch?v=TWhIM4zsmIY
• Working with Polyglot books - https://www.youtube.com/watch?v=QAz95CSiDy0
• Linux installation - https://www.youtube.com/watch?v=NXeR6J0_rXA
• Setting up Stockfish on Linux - https://www.youtube.com/watch?v=m-qWoTGNIXg