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I installed the plus4 app, and it is just a mastermind clone.

+x means you have x numbers in the right spot, and -x means you have x numbers right, but they are in the wrong spots.  It could be that a guess would result in +2-2, meaning that you have all the right numbers, but two are in the wrong spots.

Spoiler

6437 +1

From this we can see that exactly one of these numbers is correct, and also happens to be in the right position.  Looking at the column that 6 is in, you can find another guess with 6 in the first position, so 6 cannot be in the answer.  Similarly with 4.  So either 3 is in the 3rd position or 7 is in the last position.

1875 -2  and 6872 -2

Since we know 6 is not in the answer, and switching it to 1 doesn't change the result... we know 1 is also not in the answer.

1479 -2

We know 1 and 4 are not in the answer, so 7 and 9 must be.  Since we determined only one of 3 and 7 were going to be in the answer, 3 is not in the answer.  Also, 7 is in the last position due to 6437 resulting in +1.  So the answer known so far is XXX7, which includes a 9 somewhere.

1875 -2 and 3285 -2

Since we know 1 is not in the answer and 7 is, exactly one of 8 or 5 is in the answer.  Looking at the second line I listed here, since 3 is not in the answer and only one of 8 and 5 is, 2 must be in the answer.  So the answer known so far is XXX7, including a 2 and 9 and one of 8 or 5.

Looking at the columns that 2 appears in, you'll notice that it has been guessed in each column except the third, and has always been in the wrong position.  So it must be in the third spot.  So the answer so far is XX27, including a 9 and one of 8 or 5.

2048 -2

We know 0 and 4 are not in the answer since the answer is some permutation of 297 and 8 or 5.  This means 8 must be in the answer.  So the answer is either  9827 or 8927.

1875 -2

Since 8 is in the wrong position in this guess, the answer must be 8927.

So if you happened to keep the game on and check back to brainden hoping to find an answer, you can enter 8927 and win ## Join the conversation

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