Turing's Last Cipher — decrypt a message no one ever actually wrote (opens in new tab)

This is a submission for the What I built Turing's Last Cipher is a text-based cipher/puzzle adventure. A plain envelope arrives, postmarked June 21st, full of jumbled letters and one typed line: "For whoever still cares to listen. — A.T." Your terminal blinks awake, an AI assistant introduces itself, and together you start decrypting what Alan Turing supposedly never finished saying. You solve real ciphers — Caesar, Atbash, Vigenère, a dial-it-yourself Enigma — across four chapters. But the ...