Bulls and Cows (also known as Cows and Bulls or Pigs and Bulls or Bulls and Cleots) is an old code-breaking mind game.
A player should guess a 4-digit (can be 3 or 5-digit) secret number. The digits must be all different.
The "yellow" number means that player guessed the digit but not a place in the number.
The "green" number means that player guessed the digit and it's on correct place.
Game difficulty has been added.