Two players each choose a five digit 'number'. The object of the game is to discover your opponent's 'number' before he or she discovers yours. 'Numbers' are strings of five digits. selected from the possibles 0..9. The five digits in a 'number' have to be different. The players take turns to make a 'guess'. In response to a guess, the opposing player gives a score as two numbers described as "Bulls" and "Cows". You score a bull for each digit in the guess that matches the corresponding digit in the target 'number' — same digit in the same position. You score a cow for each digit that matches a digit of the target but in a different position.

For example:
If my 'number' is "01234" and your guess is "13794", you get one bull and two cows. The "4" is a bull and the "1" and "3" are cows.

In this computer version, the computer will always give the human the first guess. This is an advantage.

Operation of the computer version should be pretty intuitive. Input is through the virtual numeric pad. You can also use a connected physical keyboard, use return/enter for "ok" and delete/backspace for "cancel".

Bulls and Cows — Rules