I've posted on this before but I can't find my old post so I'm reposting sorry. Once again, if this has been posted on elsewhere direct me there and I'll go there.

I've noticed that in every Sudoku I've solved there is a pattern that forms with each pair of 3X3 boxes directly opposite the center box (top and bottom, left and right, etc.) Each box seems to be the horizontal and vertical opposite of the other in relation to number positions, i.e. if you flipped each box horizontally and vertically the numbers would be in the same places as its pair but the numbers wouldn't necessarily be the same.

Example (X means no number):

Upper left box

3 X X

X 4 6

X X 5

Upper right box

2 X X

7 1 X

X X 8

1. Flip 1st box horizontally

X X 3

6 4 X

5 X X

2. Flip 1st box vertically

5 X X

6 4 X

X X 3

The numbers are in the same position as the 2nd box (see above) but the numbers themselves do not match.