Bonus Puzzles from the UKSC

So the 2025 UKSC has been and gone.  Here are a couple of variations of puzzles that appeared on the contest, created by removing some given digits and cages. I checked with solving tools that each had only 1 solution, but to me both seemed too hard to understand fully.  What I can say is that both of these puzzles were set with particular attention paid to the grid geometry - in particular using intersection theory/SET patterns.

On the classic - perhaps there's more to be done with Phistomefel ring?  However as far as I can tell you end up losing the two sets of hidden pairs that set up the solve for the competition puzzle.

On the classic - there's all sorts going on with the larger 2x2 checkerboard combination - but it also seems to me that there's some stuff that limits the permutations within those 2x2s.  The configuration doesn't work with a pure 2x2 grid - you need the L trimino cages in order to disambiguate the solution; that said I think they should be working with the larger checkerboard layout in exactly the same way.  Or not!

It would be interesting to see if any of my dearest readers is able to share any insight.  I would say enjoy, but in this case I'm not 100% sure that experience is guaranteed!

    #363 Sudoku – rated 10/10 [Extra Hard]

    #364 Killer Sudoku – rated 10/10 [Extra Hard]

All puzzles © Tom Collyer 2009-25.