Added a Vignere cipher extension to the Ceasar cipher py file

Caesar_Cipher/Vignere_README.txt

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+<!--Please do not remove this part-->
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+
+# Vigenère Cipher: Classical Text Encryption
+
+<p align="center">
+<img src="assests/main.png" width=40% height=40%>
+
+## 🛠️ Description
+
+This script implements the **Vigenère Cipher**, a classic polyalphabetic substitution encryption technique. It accepts a keyword from the user to encode and decode messages. The same keyword must be used to decrypt the output, making it a lightweight reversible encryption tool. This is a great intro project for learning about ciphers and key-based text transformations.
+
+The script demonstrates:
+1. A `VigenereCipher` class with methods to encrypt and decrypt alphabetic strings
+2. Character-level transformation based on a repeating keyword
+3. Custom `transform()` logic that handles both encryption and decryption
+
+Feel free to enhance it with non-alphabet support, file-based encryption, or use it inside a larger pipeline.
+
+## ⚙️ Languages or Frameworks Used
+
+- Python 3.x standard library only
+- No external packages required
+
+## 🌟 How to run
+
+To execute the script, run the following in your terminal:
+
+```bash
+python vigenere_cipher.py
+```
+
+When prompted:
+- Enter a **keyword** to serve as the encryption key
+- Enter the plaintext you'd like to encrypt
+- The script will output the encrypted text and decrypt it back immediately
+
+Use `CTRL + C` to exit at any point.
+
+## 📺 Demo
+
+An example prompt might look like:
+
+```
+Enter encryption keyword: lemon
+Enter text to encrypt: hello world
+Encrypted text: siprb xbpqe
+Decrypted back: hello world
+```
+
+<img src="assests/colorgame.png" width=40% height=40%>
+
+## 🤖 Author
+
+Script by Dr. rer. nat. Nenad Balaneskovic.
+
+Nenad Balaneskovic → [GitHub Profile](https://github.com/NenadBalaneskovic)
+
+Feel free to contribute your own enhancements or port this into other encryption schemes!

Caesar_Cipher/vignere_cipher.py

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+class VigenereCipher:
+    def __init__(self, keyword: str):
+        self.keyword = keyword.lower()
+        self.alphabet = 'abcdefghijklmnopqrstuvwxyz'
+
+    def shift_char(self, c, key_c, encode=True):
+        if c not in self.alphabet:
+            return c
+        shift = self.alphabet.index(key_c)
+        if not encode:
+            shift = -shift
+        return self.alphabet[(self.alphabet.index(c) + shift) % 26]
+
+    def transform(self, text: str, encode=True):
+        text = text.lower()
+        result = []
+        key_len = len(self.keyword)
+        for i, c in enumerate(text):
+            key_c = self.keyword[i % key_len]
+            result.append(self.shift_char(c, key_c, encode))
+        return ''.join(result)
+
+    def encrypt(self, text: str) -> str:
+        return self.transform(text, True)
+
+    def decrypt(self, text: str) -> str:
+        return self.transform(text, False)
+
+if __name__ == "__main__":
+    keyword = input("Enter encryption keyword: ").strip()
+    cipher = VigenereCipher(keyword)
+
+    plaintext = input("Enter text to encrypt: ").strip()
+    encrypted = cipher.encrypt(plaintext)
+    print(f"Encrypted text: {encrypted}")
+
+    decrypted = cipher.decrypt(encrypted)
+    print(f"Decrypted back: {decrypted}")