Techniques

The contains field of a card lists techniques by three-letter code, Andrew Stuart's (sudokuwiki.org) where he has the strategy. A step is named by the most specific shape found: a Skyscraper is SKY, not X-Chain. Special case of names the next more general technique: an X-Wing is a special case of a Skyscraper, so if you know Skyscrapers you can solve an X-Wing step. Each family is sorted by band. The links go to explanations on other sites.

This page is generated from pencilmark/data/codes.csv, techniques.csv and docs/technique_links.csv (tools/gen_techniques_md.py).

Singles

Code	Technique	Band	Special case of
`FHS`	Full House	Very Easy	`HSI`, `NSI`
`HSI`	Hidden Single	Very Easy
`LSI`	Line / dot read without notes (variant)	Very Easy
`CSI`	Last cell of a cage / line (variant)	Very Easy
`NSI`	Naked Single	Easy

Intersections and rule combinations

Code	Technique	Band	Special case of	Learn
`CFX`	Clue Facts (variant)	Very Easy
`PPR`	Pointing / Box-Line Reduction	Easy
`SNY`	Snyder notation (box pairs)	Easy
`CGC`	Killer cage combinations (variant)	Easy
`SUM`	Sum clue combinations (variant)	Easy
`ARW`	Arrow sums (variant)	Easy
`RNB`	Renban runs (variant)	Easy
`IOU`	Innies & outies (rule of 45) (variant)	Easy
`PWC`	Pair rules (dots, whispers, anti-knight...) (variant)	Easy
`TBL`	Allowed combinations of a rule (variant)	Easy
`LNR`	Line ranges (thermo / whisper bounds) (variant)	Easy
`LNS`	Local line scan (variant)	Easy
`LNC`	Line classes (low/high, odd/even) (variant)	Easy
`SWC`	Sandwich sums (variant)	Easy		sugurupuzzles.com
`XSC`	X-Sums (variant)	Easy
`SKC`	Skyscraper clues (variant)	Easy
`CNT`	Counting clues (variant)	Easy
`CSH`	Clue Shape (variant)	Easy
`EQD`	Equal cells (same digit) (variant)	Medium
`DGC`	Digit counting (variant)	Medium
`LOL`	Set theory (law of leftovers)	Medium
`IOV`	Innies & outies as a virtual cage (variant)	Medium
`IOM`	Innies & outies over several houses (variant)	Medium
`EQS`	Equal sums (zipper / region-sum lines) (variant)	Medium
`CBL`	Must-contain digits (cage / line) (variant)	Medium
`RUL`	Two rules together (variant)	Medium
`IMH`	Hidden regions (implied houses) (variant)	Medium
`DOM`	Domino pairs (dots / XV) (variant)	Medium
`CLC`	Odd/even & high/low counting (variant)	Medium
`SBD`	Min/max sum bounds (variant)	Medium
`PHI`	Phistomefel Ring	Hard	`LOL`
`PHV`	Phistomefel Variant	Hard	`LOL`
`SAL`	Sum algebra (house totals) (variant)	Very Hard
`WEI`	Weighted sums (variant)	Very Hard

Subsets

Code	Technique	Band	Special case of
`MSI`	Pair / triple in the head	Easy	`NPR`, `NTR`
`NPR`	Naked Pair	Medium
`HPR`	Hidden Pair	Medium
`NQD`	Naked Quad	Medium
`HQD`	Hidden Quad	Medium
`NTR`	Naked Triple	Medium
`HTR`	Hidden Triple	Medium
`CPS`	Cage combination positions (variant)	Very Hard
`CLI`	Clique house (all-different cells) (variant)	Very Hard
`RNS`	Renban sets in a house (variant)	Very Hard
`OCL`	Outside clues together (variant)	Very Hard

Fish and wings

Code	Technique	Band	Special case of
`XWG`	X-Wing	Hard	`FRK`, `FXW`, `SKY`, `SWF`
`SWF`	Swordfish	Very Hard
`FXW`	Finned X-Wing	Very Hard	`XCL`
`FSW`	Finned Swordfish	Very Hard
`YWG`	Y-Wing	Very Hard	`XYC`
`XYZ`	XYZ-Wing	Very Hard	`ALS`
`URC`	Unique Rectangle	Very Hard
`BUG`	BUG	Very Hard
`JLF`	Jellyfish	Very Hard
`FJF`	Finned Jellyfish	Very Hard
`WXZ`	WXYZ-Wing	Very Hard	`ALS`
`FRK`	Franken Fish	Very Hard
`FIR`	Fireworks	Very Hard
`GSY`	Gurth's Symmetry	Very Hard

Chains and colouring

Code	Technique	Band	Special case of
`CCL`	High / Low and Odd / Even Colouring (variant)	Medium
`SKY`	Skyscraper	Hard	`TUR`
`KTE`	2-String Kite	Hard	`TUR`
`TUR`	Turbot Fish	Hard	`XCL`
`SCL`	Simple Colouring	Hard	`XCL`
`MCH`	Short chain in the head	Hard
`ERE`	Empty Rectangle	Very Hard	`TUR`
`RMP`	Remote Pairs	Very Hard	`XYC`
`XCL`	X-Chain	Very Hard	`AIC`
`CRP`	Chute Remote Pairs	Very Hard
`BAN`	Band set theory with cages (variant)	Very Hard
`CAL`	Equal-digit colouring (variant)	Very Hard
`AIC`	Alternating Inference Chain	Expert	`AAC`
`NLP`	Nice Loop	Expert	`AIC`
`CAS`	Case analysis	Expert
`XYC`	XY-Chain	Expert	`AIC`
`MCL`	Multi-Colouring	Expert	`XCL`
`3DM`	3D Medusa	Expert

Almost locked sets

Code	Technique	Band	Special case of
`ALS`	ALS-XZ (almost locked sets)	Expert	`AAC`
`AXY`	ALS-XY-Wing	Expert	`AAC`, `DEB`
`SDC`	Sue de Coq	Expert
`APE`	Aligned Pair Exclusion	Expert
`AAC`	ALS chain	Expert
`DEB`	Death Blossom	Expert

Trial and forcing

Code	Technique	Band
`EWY`	Either way (case split)	Expert
`WIF`	What if…	Expert
`STR`	Short trial	Expert
`FCH`	Forcing Chains	Extreme
`FNT`	Forcing Nets	Extreme
`NFC`	Nested Forcing Chains	Extreme
`NIS`	Nishio	Extreme
`POM`	Pattern Overlay	Extreme
`TRL`	Trial and error	Extreme

Singles​

Intersections and rule combinations​

Subsets​

Fish and wings​

Chains and colouring​

Almost locked sets​

Trial and forcing​