Difficulty ratings in Sudoku Explainer v1.2.1

Summary

1.0: Last value in block, row or column
1.2: Hidden Single in block
1.5: Hidden Single in row or column
1.7: Direct Pointing
1.9: Direct Claiming
2.0: Direct Hidden Pair
2.3: Naked Single
2.5: Direct Hidden Triplet
2.6: Pointing
2.8: Claiming
3.0, 3.2, 3.4: Naked Pair, X-Wing, Hidden Pair
3.6, 3.8, 4.0: Naked Triplet, Swordfish, Hidden Triplet
4.2, 4.4: XY-Wing, XYZ-Wing
4.5 - 5.0: Unique rectangles and loops
5.0, 5.2, 5.4: Naked Quad, Jellyfish, Hidden Quad
5.6 - 6.0: Bivalue Universal Graves
6.2: Aligned Pair Exclusion
6.5-6.9: X-chains/X-cycles (common 6.5-6.8; rare 6.9)
6.6-7.0: Y-cycles (common 6.6-6.8; rare 6.9-7.0)
7.0-8.0: Bidirectional Cycles (common 7.0-7.2; rare 7.3+)
7.1-7.5: Forcing Chains (common 7.1-7.3; rare 7.4-7.5)
7.5: Aligned Triplet Exclusion
7.6-8.1: Nishio (common 7.6 and 7.8; semi-rare 7.7 and 7.9; rare 8.0-8.1)
8.2-8.7: Cell/Region Forcing Chains (common 8.2-8.5 (8.2 only for region); rare 8.6-8.7)
8.8-9.6: Dynamic Forcing Chains (common 8.8-9.4; rare 8.7 and 9.5(9.6?))
9.1-10.1: Dynamic Forcing Chains(+) (common 9.4-10.1; rare 9.3 and 10.2; ?9.1-9.2)
9.9-11.0: Dynamic Forcing Chains(+Forcing Chains) (common 10.2-10.7;
          rare 10.1 and 10.8 - 11.0; ultra rare 9.9-10.0)
10.8-11.5?: Dynamic Forcing Chains(+Multiple Forcing Chains) 
11.4-11.9: Dynamic Forcing Chains(+Dynamic Forcing Chains) 12.0-12.7(Pencilmarks)

Details

Difficulty ratings are represented by a positive number rounded to the tenths digit. Rating is formed by

• Base difficulty for the used technique.
• Complexity modifier accounting for details within the used technique.
• Preceding technique modifier accounting for relationship between currently used technique and the technique from the preceding step.

In addition to the rating number, a rating ordering attribute is used to distinguish the preferred technique within the possible techniques that evaluate to the exactly same rating number.

After resolving particular cell to particular value, direct eliminations of the potential values for all 20 cells that share the same Row/Column/Box are always applied and not considered as solving technique.

GUI

The hints in GUI are given in ascending order considering the above rules.

Batch processing

The top technique is automatically chosen and applied until the solution is found.