SudoCue Users

Let me try to recover from my XYZ wing SNAFU. :roll: :oops: Here's an implication attack through MJ's UR 'B' to show that r4c5 = 4 only if the puzzle is invalid. First use MJ's XYZ wing to clear 4 from r4c46, then suppose that r4c5 = 4: r4c5?=4 -> r4c1=5, exposing the bottom of 'B'; r6c3 is the corn...

Don't worry about the notation. Mine is not standard either. I don't see how r8c6, r9c5, and r5c6 legitimately kill a 4 in r4c5. In order to be killed, the target candidate needs to see all of the 4's in the xyz-wing cells, right? r4c5 cannot see the 4 in r8c6. I think this xyz-wing should only be ...

Also, there's an XYZ wing at r8c6: r9c5, r5c6 (sorry 'bout the unconventional notation) which kills the 4 at r4c5. If you happen to find this one first, it reduces the original XYZ wing to an XY wing. IAE, after both wings the result is that r5c6 = 4 and, except for one instance of coloring, it's al...

An alternative solution appears when you notice that block 7 is a crossroads for several implication chains, for which R8C3 can be taken as a root. Setting R8C3 to 7 forces a contradiction in '5' at R3C57 so R8C3=5, leading directly to the solution.