I'm making this up from memory from sometime in the mid 1970s.

I'm hope I am not stepping on anybody's copyright. If it turns out I am, I'll refer to and point to the source if that's ok, or delete this altogether if not.

This game uses some of the same synapses used in debugging computer programs and digital designs.

Both players make up a 5 digit number where none of the digits repeat. The number is the secret number and is not revealed.

In turns, each player makes a guess of the other's secret number.

The player guesses the other by coming up with their own 5 digit guess. The guess can't have any repeated digits. 12456 is a valid guess. 12315 is against the rules.

The defender answers by telling the count of digits matching the secret # and in the correct place, and the count of digits which were found in the secret # but are in the wrong place.

The code used for the answer is ** Fox** is a correct number and in the correct place.

Each number in the guess is only counted once. So if the secret number is 12345 and the guess is 12459 then the answer is Fox Fox Hound Hound for two correct digits in the correct place, and two correct digits in the wrong place.

We abbreviate the result as FFHH when running the game over a text medium like packet, or when making notations during play. It is ideal to put the Foxes first, and hounds after, to obscure the order in which the digit matches are discovered.

Time limits during play should be negotiated up front. Generally speaking a meticulous player will want as much as 15 minutes per step when they are about to pounce and win. Limiting them to 2 minutes is cruel so go ahead and do that.

So... Player A makes up 24680 and Player B makes up 21905

etc..A guesses 12345 B guesses 12345 A answers FHH B answers HH A guesses 34589 B guesses 67890 A answers HH B answers HH A guesses 35891 B guesses 67345 A answers HHH B answers HH A guesses 16705 B guesses 23467 A answers FFH B answers FHH

As the player answers each guess, they have to be really careful. The players must keep track of their secret number, the apponent's guesses, and the answers given.

If player A discovers that there must be a mistake in one of player B's answers, player A can call a foul.

There can be several resolutions to this.

- Player B finds the mistake and player A gets to make all of his guesses after the mistake, over again.
- Player B claims there is no mistake and convinces player A. If Player A concedes there is no mistake, player B gets to take a # of free moves equal to the number of moves player A has taken so far.
- Only if Player A maintains there is a mistake and player B maintains there is no mistake, then PLayer B releals his secret number.
- If player A discovers and proves the mistake, Player A wins.
- If player A cannot show the mistake, Player B wins.

Experienced and meticulous players can take 10 guesses to complete, while new players can take 20 or so.
In order to win in the fewest guesses, the players will take maticulous notes of their own guesses and what they can determine from the responses.
For instance, if a guess of 12345 gets a response of HHH (i.e 3 correct digits out of the five) and a followup guess can be made of 54326, if the response is FH (i.e. 2 correct digits out of the 5) then the player can see that swapping a 1 for a 6 reduced the number of correct digits.
This would indicate that the 6 is not a good digit, and the 1 *is* a good digit. Five such successful swaps would indicate all 5 required digits.
Now the ordering of digits is the key.

Have fun!