fill project description

README.md

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 # 15 Puzzle game with Go
 
+🚀 [Play in Telegram](https://t.me/puzzle_15_bot?startapp).
+Game has [simple rules](https://en.wikipedia.org/wiki/15_puzzle).
+
+## Description
+
+The intentions of the project is to create a simple proof-of-concept demonstrating that a [Telegram Mini App](https://core.telegram.org/bots/webapps) can be developed with Go and [WebAssembly](https://go.dev/wiki/WebAssembly).
+
+✨ Graphics are made with [Ebitengine](https://github.com/hajimehoshi/ebiten).
+
+Basic "features" include: a splash screen, game move sound, a switchable silent mode without moves count,
+a players' rating table, a congratulations screen for achieving 1st place,
+a pin-code protected game statistics screen,
+and backend API requests secured through [data validation](https://core.telegram.org/bots/webapps#validating-data-received-via-the-mini-app).
+
+## Running game
+
+Local gameplay can be initiated using the following command:
+
+```shell
+go run ./cmd/ui
+```
+
+A fully functional Mini App requires a web server.
+You can use [`Dockerfile`](Dockerfile) to build a Docker Image
+containing all necessary artifacts: the server binary, the WebAssemply (wasm) binary, and html page.
+Certain environment variables should be set for the server to start:
+
+| Env                | Description |
+| -                  | -           |
+| **`BOT_TOKEN`**    | Telegram Bot [API Token](https://core.telegram.org/bots/tutorial). |
+| **`DATA_FILE`**    | Path to the file where games data will be stored. |
+| **`ACCESS_CODE`**  | Pin-code to access the Statistics Screen. |
+| **`PROJECT_LINK`** | URL to the project's source code. |
+| `SERVER_PORT`      | Port for the server to listen for API requests, defaulting to `8080` if not set. |
+| `CONTEXT_ROOT`     | Server requests URI root path, defaulting to `/` if not set. |
+| `STATIC_DIR`       | Directory where static files are located, defaulting to the current directory if not set. |
+
 ## Credits
 
-- [Gopher by gheimifurt](https://www.reddit.com/r/golang/comments/xdxb9a/gopher_ascii_art_for_bashrc/).
+- [Ebitengine](https://github.com/hajimehoshi/ebiten) game engine by Hajime Hoshi.
+- Font by [VileR](http://int10h.org) and [fly_indiz](http://old-dos.ru/index.php?page=files&mode=files&do=show&id=102798).
+- ASCII Gopher by [gheimifurt](https://www.reddit.com/r/golang/comments/xdxb9a/gopher_ascii_art_for_bashrc/).

internal/puzzle/assets/fonts/README.md

@@ -2,5 +2,5 @@
 
 Credits:
 
-- [VileR](http://int10h.org/).
+- [VileR](http://int10h.org).
 - [fly_indiz](http://old-dos.ru/index.php?page=files&mode=files&do=show&id=102798).