Learning path

8 chapters, easiest technique first.

The path decides what you learn next, so you never open a forcing chain before you can spot a single. Every stop pairs a written explanation with worked examples on a real board. Browse the technique library instead.

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FoundationsSummit

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Foundations

How the grid constrains itself, and how to keep notes you can trust.

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Reading the Grid

The first stop on the path. How a sudoku grid is built from rows, columns and boxes, how every cell gets its name, what givens are, and the one rule that decides which digits a cell can still take.

3 min readReading only — no worked examples for this one yet

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Pencil MarksWhat a candidate is, how to write pencil marks and where this site puts each digit, when to mark every cell and when one box is enough, and how to cross marks out when a digit goes in.4 min

Singles

Placing digits. The only family that fills cells rather than clearing notes.

Unlocks after Foundations

3 techniquesLast Possible NumberNaked Single vs Hidden SingleHidden SingleRead ahead in the library

Locked candidates

Where a box and a line overlap, one constraint leaks into the other.

Unlocks after Singles

2 techniquesPointing Pairs and TriplesClaiming Pairs and TriplesRead ahead in the library

Subsets

Groups of cells that own a group of digits. Nothing gets placed — notes get cleared.

Unlocks after Locked candidates

4 techniquesNaked PairHidden PairNaked TripleHidden TripleRead ahead in the library

Fish

One digit, boxed into a rectangle of rows and columns.

Unlocks after Subsets

3 techniquesX-WingSwordfishJellyfishRead ahead in the library

Wings

A pivot cell that sees two wings, forcing a shared conclusion.

Unlocks after Fish

3 techniquesY-WingXYZ-WingW-WingRead ahead in the library

Chains & coloring

Alternating links that carry a conclusion across the whole grid.

Unlocks after Wings

20 techniquesSimple ColoringX-ChainX-Chain Cell GroupsShort AIC+16Read ahead in the library

ALS & exotics

The summit — almost-locked sets, uniqueness, and the techniques built on them.

The summit

7 techniquesBUG+1Restricted Common CandidateAligned Pair ExclusionAligned Triple Exclusion · Coming later+3Read ahead in the library