🔐 Caesar Cipher Encryption & Decryption (Plain JavaScript)

A lightweight, fully functional implementation of Caesar Cipher built using HTML, CSS, and vanilla JavaScript — no frameworks, no dependencies.
It allows users to encrypt and decrypt text messages or .txt files using a simple shift key logic.

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🚀 Features

✅ Client-side only (no backend required)
✅ File upload support (.txt) – automatically reads content for encryption/decryption
✅ File download – saves the encrypted/decrypted message as .txt
✅ Responsive, modern UI with a styled interface
✅ Instant encryption and decryption using ASCII shift logic

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🧠 How It Works

The Caesar Cipher is a basic substitution cipher where each character in the plaintext is shifted by a given integer key.