How Swudoku helps you warm up for competitive chess

If you play chess, this is a short warm-up. It is not study, and it will not move a rating.

What it is: a daily 9×9 Swap Sudoku with no timer, where the only score that matters is how few swaps you needed. If you want your brain in “think, then move” mode before a club game, that’s a decent shape of warm-up. It will not replace tactics books, endgame drills, or sitting at a real board.

Same habit as a slow game

Blitz rewards the first idea that doesn’t lose on the spot. A long game rewards the second look.

Swudoku is built like the second kind. The board is already full. You swap. You don’t fill. Nothing is counting you down. You can stare at two grey tiles until you’re sure they want each other’s cells. A Double Swap (both tiles correct in one move) feels a bit like finding a tactic that does two jobs. A shrug-swap that only parks one tile is the cheap check that creates a new mess.

If you play chess, you already know this muscle: calculate a line, decide it isn’t worth the tempo, look again.

Patterns, then a concrete move

You don’t need opening theory. You need to see.

Grey means the number is in the wrong cell. Yellow is home, but the row, column, and block are unfinished. Green is home plus any one of those three complete. Dark green is all three. You’re scanning for collisions the way you’d scan a file for a loose piece, then you spend a move.

Working a 3×3 block until it lights up is similar to fixing a sector of the board before you invent a kingside attack. Undo exists if the line was wrong. How to play covers that. It doesn’t cost rating points, because there are none.

Why no clock matters here

A chess clock is part of the sport. A puzzle timer is just someone else’s idea of pressure.

Warming up without a flag hanging over you is useful if your actual match will have a clock. You get a few minutes of clean calculation, then you walk to the board. Most people spend about 3–5 minutes on a Swudoku.

Everyone gets the same daily grid, so you can compare swap counts with a training partner the way you’d compare a shared tactics set. Signed-in finishers may see a How you compare histogram for that puzzle. It is still not a rating.

Classic sudoku logic shows up because rows, columns, and blocks still want 1–9 once each. The mechanic is swapping. That is the whole analogy.

Play on the web or in the iOS app. Same account syncs game stats both ways. Archive (past days) is on the web when you’re signed in; iOS is today’s board.

Warm up on today’s board

If you’ve got a match later, do one quiet grid first. Play today’s Swudoku, take the swaps you need, then go play chess.

Colours and scoring, without the chess talk: FAQs.