Caesar Cipher

No — only the Latin alphabet is rotated. Cyrillic characters pass through untouched, so a Russian phrase stays perfectly readable and is not really enciphered at all. If your assignment requires the thirty-three-letter Russian alphabet, transliterate first or work the shift table by hand, because the ring has a different length.

They stay exactly where they are; only letters move. That keeps the shape of the sentence and any dates intact, which is convenient — but it is also a gift to anyone attacking the message, since word lengths and punctuation give the plaintext away almost immediately.

Yes. An uppercase letter stays uppercase and a lowercase one stays lowercase; only the alphabet position changes, which is why ATTACK becomes DWWDFN in full caps. Bear in mind that preserved case also helps a codebreaker, as proper nouns and sentence starts remain visible.

Not remotely. There are only twenty-five possible shifts, a person can try them all in about a minute, and frequency analysis breaks it faster still. Treat it as a teaching and game device — puzzle hunts, notes, homework. Anything you actually need protected deserves real cryptography.

ROT13 is the same cipher with the shift nailed to thirteen. Because the Latin alphabet has twenty-six letters, encryption and decryption are then the same operation. Here you choose the step, which is why there are two separate buttons for Encrypt and Decrypt.

The field accepts 1 to 25, and for good reason: a shift of 0 or 26 returns the text unchanged, since the alphabet turns a full circle. A shift of 27 is identical to 1, and 30 is identical to 4, so anything outside the range simply repeats a value already available.