Chess Steganography
If anything the "one-sided" mode is even more fun: <a href="https://incoherency.co.uk/chess-steg/oneside.html" rel="nofollow">https://incoherency.co.uk/chess-steg/oneside.html</a><p>It lets you interactively encode a message in your moves when playing against a player who is not in cahoots with you :)<p>(Disclosure: I made this).<p>And yeah, sorry about the lack of error-checking. If pretty much anything goes wrong it (maybe) writes an error to the console, and just does nothing.<p>I'd be interested to see if anybody can produce a short message which can't be encoded because it results in a state where the only legal moves are checkmate.