Here's a starter:

- Code: Select all
`*-----------*`

|..2|..7|...|

|..4|...|..5|

|9.6|...|81.|

|---+---+---|

|...|...|34.|

|2..|.1.|...|

|.8.|..5|7..|

|---+---+---|

|.4.|8.1|.6.|

|...|...|...|

|3..|69.|...|

*-----------*

This puzzle solves with singles, locked candidates and one naked triplet. Now what if the solver cannot see the naked triplet? Here's the path Sudoku Explainer will take if the triplet is ignored:

Nishio Forcing Chains: 2

Region Forcing Chains: 3

Dynamic Region Forcing Chains: 1

Dynamic Contradiction Forcing Chains: 2

Explainer rating: 8.9

Sudocue also finds it quite hard when I turn of all subsets:

XYZ-wing: 1

APE: 3

Finned swordfish: 2

Tabling: 19

Total score: 16180

If I allow sudocue to use naked and hidden pairs, then it's enough with 10 tabling steps...

What can I say, better learn your basic techniques well! What's the tightest bottleneck you can find? Hint on finding tight bottlenecks: If suexrat gives > 400 points and gsf's program < 100, then there probably is a tight bottleneck that solves with subsets. Apparently suexrat doesn't find naked triplets...

RW