Tutorials.
A short guide to variant sudoku and how to use Sudorix.
Sudoku, briefly
Standard sudoku is a 9×9 grid divided into nine 3×3 boxes. Place the digits 1–9 in each cell so that every row, every column, and every box contains all nine digits exactly once. That's it.
Variant sudoku starts there and adds extra rules — colored lines, dotted edges, killer cages, weird shapes outside the grid. The extra rules give the puzzle its flavour and make solving more than just process-of-elimination on rows and columns.
Constraint types
Common variant constraints you'll see across Sudorix puzzles. Always read the puzzle's specific rules — setters can layer constraints together or tweak the standard meanings.
Thermometer
A grey "thermometer" shape on the grid. Digits along the thermometer must strictly increase from the bulb (round end) to the tip.
Arrow
An arrow points from a circle to a line of cells. The digit in the circle equals the sum of the digits along the arrow.
Killer cage
A dashed outline around a group of cells, often labelled with a number. Digits inside the cage must sum to that number, and (typically) cannot repeat.
Kropki dots
Small dots between two cells. A white dot means the digits are consecutive; a black dot means one is double the other. Some puzzles state that all valid dots are shown — pay attention to the rules.
XV
An X between two cells means the pair sums to 10. A V means the pair sums to 5. Same negative-constraint caveat as Kropki — read whether all valid Xs and Vs are shown.
German whispers
A green line. Adjacent digits along the line must differ by at least 5.
Renban
A purple line. The digits along the line must be a set of consecutive numbers, in any order, with no repeats.
Palindrome
A grey line where the digits read the same forwards and backwards. The first digit equals the last, the second equals the second-to-last, and so on.
Little killer
An arrow outside the grid with a number. The digits along the diagonal the arrow points down must sum to that number.
Sandwich
A clue outside a row or column. The digits between the 1 and the 9 in that row/column must sum to the clue.
Fog of war
Most of the grid is hidden under fog. Placing a correct digit reveals the cells around it, exposing more of the puzzle as you solve. Wrong digits stay covered.
More constraint types (regions, killer with subtraction, sum arrows, etc.) coming as we expand this page. If a puzzle uses a constraint not listed here, the setter's rules will explain it.
Watching, learning
The fastest way to get good at variant sudoku is to watch someone good solve one and explain their thinking. The Cracking The Cryptic channel on YouTube has thousands of solves with full think-aloud commentary, sorted by constraint type and difficulty. Pick a constraint you don't get yet, find a video that uses it, watch one solve.
Importing a puzzle
Sudorix imports from full URLs. Paste any of these into the Importer in your Library:
- SudokuPad puzzle URLs (e.g.
sudokupad.app/abc123) - Penpa+ URLs (with the
p=parameter) - F-puzzles URLs
- puzz.link URLs
Short SudokuPad IDs aren't a setter feature — paste the full URL instead.
The publishing flow
Every puzzle you import or set moves through four states:
- Raw — just imported. Only you see it.
- Testing — you've approved it for testing. Still private to you.
- Awaiting publish — you've submitted it for publishing. An admin will review it.
- Published — visible to everyone in the Library.
Each step has a button on the puzzle's card in your Library that promotes it to the next state.