Sudoku Technique Walkthroughs

How to use a walkthrough

The temptation with a worked example is to scroll straight to the after-image and check that the explanation makes sense. Resist it. Reading a solution builds the feeling of understanding without building the skill, because the hard part of a technique is not following the logic once the pattern is pointed out — it is finding the pattern on a board where nobody has pointed at anything.

Get the value out of these pages by working them in this order:

1. Read the technique's definition at the top of the page, then stop.
2. Study the before-image and find the pattern yourself. Each walkthrough tells you which unit or which digit is involved, so the search is bounded — but it is still a search, and that search is the entire exercise.
3. Predict what will be eliminated before you scroll. Naming the affected cells in advance is the test of whether you have understood the deduction or merely recognised the shape.
4. Then compare against the after-image, where removed candidates are struck out in red and newly solved cells shown in green.
5. Read the notes below the boards on why the deduction is valid, how to spot the pattern unaided, and what to look at next.

What these boards show

Each walkthrough is a real puzzle from the library, captured at the exact moment the technique becomes available, with candidates fully pencilled in. Nothing is staged or simplified — which is why the patterns often look nothing like textbook diagrams. Real triplets are frequently partial, with no cell showing all three digits, and real Swordfish are usually ragged rather than a tidy three-by-three arrangement. Learning to verify a pattern by counting rather than by appearance is most of what makes it transfer.

There are three walkthroughs per technique, each on a different board and in a different unit, because seeing one instance is what teaches you the diagram and seeing several is what teaches you the pattern.

Where to go next

Walkthroughs show a technique firing once. To turn recognition into a habit you need repetition against live boards, which is what the technique practice pages provide — every puzzle in a set is verified to require the named move. For the reasoning behind the techniques rather than the mechanics, the long-form guides cover why the subsets work, why fish patterns are one idea at two sizes, and how difficulty is actually determined.