Steganography Cipher

How it works: Enter your cover message (null text), define rules with hidden messages (plaintext), and the ciphertext is automatically generated with plaintext embedded at rule-specified positions.

Two-level targeting: First select words, then select letters within those words.
- Word: all + Letter: all = replace every word
- Word: every 2 after punct + Letter: all = replace 2nd word after each punctuation
- Word: all + Letter: every 3 in word = every 3rd letter of every word
- Word: every 2 after punct + Letter: every 3 in word = 3rd letter of 2nd word after each punctuation

Formulas: all, first N, every N, fib, prime, n^2, 2n+1

Punctuation: . ! ? , ; : ' (includes apostrophe, so "can't" triggers the next word)