1. Caesar warm-up: brute-force all 25 shifts (the in-page tool lists them); the readable one reveals the Vigenère key is LEMON (uppercased). Why: Caesar has only 25 keys — exhaustively trivial.
2. Put the Vigenère ciphertext and key LEMON into the Vigenère decoder. Why: Vigenère is a repeating-key shift; with the key it reverses directly.
3. The decrypted Vigenère text is the flag. Enter it to confirm.
Lesson: classical ciphers provide no real security against modern analysis.