Killer Sudoku
Classic sudoku rules, plus dashed "cages" that must add up to a target sum — and never repeat a digit inside.
What makes it Killer
Instead of starting with given digits, you start with cages — connected groups of cells with a printed target sum in the corner. Every cage must hit its sum exactly, with no repeated digits inside. The classic row, column, and box rules still apply on top.
Pure-cage puzzles (no given digits) test pattern recognition over rote elimination. Cage-sum arithmetic does most of the early work.
Rules
- All classic rules: no repeats in any row, column, or 3×3 box.
- Each cage's cells must sum to the printed target.
- No digit repeats within a single cage.
How Stillgrid plays
- Cage outlines and sums rendered cleanly into the grid.
- Pencil marks and auto-pencil for candidate tracking.
- Undo/redo with full history.
- Difficulty graded by the cage logic and singles a puzzle actually requires.
- Daily killer challenge alongside the classic one.
- No signup. No ads.