Add Caesar cipher project with Doxygen docs

README.md

@@ -1,2 +1,76 @@
-# 008-caesar_cipher
+# 🔐 Caesar Cipher
 
+A beginner-friendly Python program that encodes messages with the Caesar cipher.
+
+## 📚 Table of Contents
+
+- [Overview](#-overview)
+- [Requirements](#-requirements)
+- [Setup](#-setup)
+- [Run](#-run)
+- [Tests](#-tests)
+- [License](#-license)
+- [Links](#-links)
+
+## 🧭 Overview
+
+The Caesar cipher shifts every letter by a fixed number of places (with a shift of 3, `E` becomes `H`). This project, from Udemy's *100 Days of Code: The Complete Python Pro Bootcamp* (Day 8), finds letter positions with `list.index` and wraps around the alphabet with the modulo operator. Part 1 covers encryption; decryption and a combined program follow in later parts. Code lives in `src/`, tests in `tests/`, docs in `docs/`.
+
+## 📋 Requirements
+
+- Python 3.13 or newer
+- `pytest` (development only; no runtime dependencies)
+- Optional: [Doxygen](https://www.doxygen.nl/) to build the API docs
+
+## 🛠️ Setup
+
+Create and activate a local virtual environment, then upgrade pip and install the project:
+
+```bash
+python -m venv .venv
+```
+
+Activate it:
+
+```bash
+# Linux / macOS
+source .venv/bin/activate
+# Git Bash on Windows
+source .venv/Scripts/activate
+```
+
+```powershell
+# Windows PowerShell
+.venv\Scripts\Activate.ps1
+```
+
+```bash
+python -m pip install --upgrade pip
+python -m pip install -e ".[dev]"
+```
+
+## ▶️ Run
+
+```bash
+python -m caesar_cipher
+```
+
+or, after installation, `caesar-cipher`.
+
+## 🧪 Tests
+
+```bash
+python -m pytest
+```
+
+Build the API docs with `doxygen Doxyfile` (output in `docs/doxygen/html`).
+
+## 📄 License
+
+GNU AGPL-3.0 – see [LICENSE](LICENSE).
+
+## 🔗 Links
+
+- [Repository](https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code)
+- [Documentation](docs/index.md)
+- [Issue tracker](https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/008-caesar_cipher/issues)