@freemo @trinsec mainly the problem is that the alphabet of legal characters is too small, especially relative to the length of each guess. 10 digits + 4 operations = 14 characters in the alphabet, versus 7 characters in a guess not counting the mandatory equals sign, lets you cover every possible character in your first two guesses. Yeah, you have to then figure out the permutation and watch out for duplicated characters, but it's not enough to make life difficult in the face of all the information you have by that point.