Bulls Cows: classic

This is classical logic game Cows&Bulls. The Computer make a 4 digit number. The digits are all different. Then, in turn, the player try to guess the number. If the matching digits are in different positions, they are "cows", if in their right positions, they are "bulls". Example: Secret number: 4271 Opponent's try: 1234 Answer: 2 cows and 1 bull. (The cows are "4" and "1", the bull is "2".) The first one to reveal the other's secret number wins the game. If you will guess number for 10 attempts you will win. Opposite, the computer show you number and ther make a new.