Expert sudoku – today's 4 free puzzles

Reading the whole grid as a single picture

Step into expert sudoku and the scenery changes. Up to intermediate level, local observation — this row, this box — was enough. From here on the question is whether you can read patterns in candidate placement that span distant rows and columns. Instead of one cell, you look at the mesh of candidates spread across the whole board and take it in as one image. It sounds forbidding, but the catalogue of patterns is surprisingly short, and three of them do most of the work.

X-Wing: the four corners of a rectangle

When a digit's candidates survive in exactly two places in each of two rows, and those places sit in the same two columns, the four positions form a rectangle. Whichever diagonal turns out to be true, that digit cannot appear anywhere else in those two columns — so you sweep the candidate out of both columns in one move. Plenty of solvers describe finding their first X-Wing unaided as the moment sudoku changed for them.

Y-Wing: a chain of three

Three cells, each with two candidates, linked as "AB", "BC" and "AC". Whichever value the pivot takes, you can prove that C cannot go in any cell seen by both wings. It shines in the middle and late game when two-candidate cells are everywhere. Where an X-Wing looks at the geometry of a single digit, a Y-Wing looks at the relationships between cells, completely different views of the same board. Carrying both doubles the number of ways you can break a deadlock.

Swordfish: the X-Wing on three rows

Extend the X-Wing to three rows and three columns. It is harder to spot but the logic is unchanged, and it dissolves positions that nothing else touches.

Don't search for patterns — make them surface

Everyone thinks the same thing after reading a technique guide: "I understand the shape, I just can't find it on a real board." That is a problem of where you point your eyes. Scanning the whole grid vaguely shows you nothing. The trick is to commit to one digit and follow only that digit's candidates. Decide "for the next two minutes I am thinking about 3s and nothing else", and mentally mark every cell where a 3 is still possible. The 9×9 board collapses into a sparse constellation of 3s, and rectangles with two per row rise out of it on their own. Working through 1 to 9 as nine single-colour boards takes two or three minutes once you're used to it, and it is the standard response when an expert grid stalls. Finding nothing is no loss: the pass leaves you with a much sharper mental map, and the second lap reads far faster than the first.

The case against guessing

You could always place a digit at random and back it out when it contradicts. It works, in the sense that you eventually reach the answer. Most strong solvers refuse anyway, for one simple reason: a puzzle solved by guessing teaches you nothing. Every advanced technique is just an inference that would take ten steps of trial and error, compressed into one act of pattern recognition. When you stall, go back to the board believing there is a piece of logic you haven't found yet. Solvers who hold that line are the ones who eventually see the patterns lift off the page. Every expert puzzle here is guaranteed solvable by logic alone, so you can put guessing down with confidence.

A practice plan

Knowing a technique is not the same as seeing it. The most effective drill is volume at a fixed level in a short window: play the four daily expert puzzles, then work backwards through the archive a date at a time. Pattern recognition sharpens quickly under that kind of repetition. It also pays to deliberately print a grid and solve it in pencil — without a notes button you have to hold candidates in your head, which builds the wide view the advanced patterns depend on. Come back to the screen after a week on paper and the board looks a level deeper than it did. Once the three patterns feel like weapons rather than trivia, evil sudoku is waiting, where they have to be combined.