Logic puzzle
Sudoku Nio
Sudoku that never runs out of puzzles, because it makes them on your phone. Each one is proven to have exactly one solution before you ever see it.
UNDER THE HOOD
Every puzzle is proven, not assumed
Each board starts as a finished grid. Cells are removed one at a time, and a cell is only allowed to go if a solver confirms the puzzle still has exactly one solution — it counts solutions and stops the moment it finds a second. Because the check happens at every step, there is no path through the code that can produce an unsolvable or ambiguous puzzle.
Difficulty measured by technique, not by holes
A second solver plays the puzzle the way a person would, working through singles, locked candidates, pairs, triples and X-Wings. The hardest technique it needed is the difficulty. Easy means singles are enough; Master means our technique set runs out and you will need to reason further.
Hints that teach
Ask for a hint and the game names the technique — "hidden single", "locked candidate" — and points at the square, but leaves the number for you to write. After a few of those you start seeing the pattern before the hint does.
SPECIFICATIONS