This is an advanced sudoku client built for puzzle enthusiasts who want a single tool that handles classic puzzles as well as the many popular modern variants. You can create puzzles, solve them, and switch between editor and solving modes whenever you need to.
The app supports six rule variants, three constraint types (killer cages, sandwich clues, thermometers), pencilmarks, cell coloring, automatic pencilmark generation that respects all active rules, OCR import from image files, and persistent settings — all in one self-contained page that works offline once loaded.
The app has two distinct modes. You start in Editor mode, where you can place the puzzle's given numbers, define cages, add sandwich clues, and draw thermometers. When the puzzle definition is complete, click 🔓 Lock board to switch to Solve mode.
In Solve mode, the given numbers and puzzle structure are locked. Any digits you place are shown in a different color (yours, not the puzzle's). Pressing Reset in Solve mode clears your progress but keeps the puzzle structure intact. To edit the puzzle itself, click 🔒 Unlock board to return to Editor mode.
Click a cell to select it, then type a digit 1-9. Three input modes determine what the digit does:
Switch modes by clicking the tabs at the bottom of the board, or press Space to cycle through them. Typing the same digit again removes it from a pencilmark cell. Backspace or Delete clears the selected cells.
The variant dropdown in Settings chooses which extra rules apply when solving. The variant determines what counts as an error and affects auto-pencilmarks.
Enable "Killer cages" in Settings to activate cage support. A killer cage is a group of cells whose contents must sum to a target value, with no repeated digits within the cage.
To create a cage: select the cells (drag or Ctrl+click), then click + Add cage from selection in the left panel. You'll be prompted for the cage's sum. To edit an existing cage's sum, click any cell of the cage to select it, then click Edit sum of selected cage. To remove a cage, click any cell of it and choose Remove cage from selection.
Cages are drawn with a dashed perimeter and the sum displayed in the top-left corner of the cage's smallest cell.
Enable "Sandwich clues" in Settings to add margin clues. A sandwich clue is a number outside the grid that gives the sum of all digits between the 1 and the 9 in that row or column.
In Editor mode, click the clue area in the left or top margin to enter a value (0-35). Click the same clue again to edit or clear it. Sandwich clues are validated as part of solving when the row or column is complete.
Enable "Thermometers" in Settings to add thermo support. Values along a thermometer must strictly increase, starting at the bulb and moving outward along the bar.
To draw a thermometer: in Editor mode, click the cell where the bulb should go and drag along adjacent cells (king-step adjacency — orthogonal or diagonal). A live preview shows the planned thermo. Release to confirm. To remove a thermometer, click any cell of it and use the Remove option in the thermo panel.
In Editor mode, you can import a sudoku puzzle from an image using OCR. Either drag and drop an image into the "Drop image here" area, paste an image with Ctrl+V, or click 📁 Choose image file.
The OCR reads the given digits and places them in your grid. Cages, sandwich clues, and thermometers are not auto-detected (auto- detection from images is unreliable in practice) — you'll add those manually afterwards using the editor tools described above.
When importing a killer-sudoku image (with the Killer toggle on), the OCR automatically ignores the small sum-text in the top-left corner of each cell, so cage sums won't be mis-read as digits.
Click the ⚙ button in the header. Settings persist between sessions in your browser's local storage.
Inspired by puzzles featured on Cracking the Cryptic and the wider sudoku-variant community. This is an independent hobby project and is not affiliated with, endorsed by, or sponsored by Cracking the Cryptic or any other puzzle platform.