How do you play this old unix game?

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http://unix.stackexchange.com – I recently tried the simh emulator, pdp11. The disk image I used can be found on the internet, and instructions for booting it are here. Presumably it belonged to Dennis Ritchie, as the username is "dmr". In the /usr/games folder are about 20 games and amusements for wasting expensive computing resources. One game is called 'moo'. I have not been able to find info about this game, but starting it prints: MOO new game ? Every input I have tried results in the game printing 'bad guess.' Does anyone have experience with this game? Ritchie is dead, so there's no way to ask him directly. (HowTos)