scrose wrote:Animator, help me see what I'm missing in column 3.

It's not an immediate error... (there might be one but I haven't found it).

I was able to reach this grid with r6c9 = 1: (you can fill in some more numbers too but they are irrelevant)

4 * * | * 9 1 | * * 8

3 * * | 2 * 8 | * 1 *

7 1 * | * 5 3 | * 6 *

-----------------------

* * 3 | 1 * 7 | 9 * *

* * 1 | * * 9 | 7 * *

* 9 7 | 5 * 2 | 3 * 1

-----------------------

9 6 4 | * 1 5 | 8 2 *

1 * * | 9 * 4 | 6 * 5

5 * * | * 2 6 | 1 9 4

With this grid there is only one place for the number 8 in box 1, r3c3.

And the only candidate for r9c3 is 8. This means that you have the number 8 twice in column 3. (or the number 8 and an empty cel).

I'm pretty sure there are other ways to show that this grid is impossible... as in, at one pointed I reached an error in column 1 but I no longer have that grid.