Let’s play it.
The game involves guessing a 4digit secret number through a series of strategic guesses. If players manage to guess a certain digit, and that digit is positioned in the right place the game master will inform them on their correct guesses by means of the denomination “Bull.” If players guess the digit, but the position is not the correct one, the game master will inform them on that through the term “Cow.” The first player to find the secret number will be declared the winner and will become the game master of the next round of the game.
I played this game a lot when I was in school and there are different versions. We will play the standard version here, where the 4digit number can start with 0 but the digits must be all different. Here is the description of the game on Wikipedia:
On a sheet of paper, the players each write a 4digit secret number. The digits must be all different. Then, in turn, the players try to guess their opponent’s number who gives the number of matches. If the matching digits are in their right positions, they are “bulls”, if in different positions, they are “cows”. Example:
Secret number: 4271
Opponent’s try: 1234
Answer: 1 bull and 2 cows. (The bull is “2”, the cows are “4” and “1”.)
The first one to reveal the other’s secret number in the least number of guesses wins the game.
The game is traditionally played by two players, but here the game master will pick the secret number and give the players who post their guesses the number and quality of their matches.
I can think of two problems:

The game master can change the secret number, especially in the first stage of the game. I don’t really know how to handle this situation in a practical way. In real life, players will write down the number on a piece of paper and put it aside. Thus, the number can be verified at the end of the game.

The game master can give the wrong information on the matches. I’ve come across with the situation in real life quite frequently. My friends and I solved this problem by declaring the game null and recording it as a loss for the person who gave the wrong information. I think the same rule should be followed here: If the game master (accidentally or not) gives the wrong information on Bulls and Cows, then the game master will lose the game and the player who has received the wrong information will become the winner and the game master of the new round of the game.
Here’s the first secret number:
It is a number I have extracted from a “reliable source” that I will reveal when the round ends.
Please submit your guesses and may the best “man” win!