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BoringTime Games
Sudoku
A 9×9 logic puzzle you can start from a printed page. Photograph the grid, confirm the outer frame, then solve with hints that teach the technique instead of dumping the next digit.
Rules Photo scan Powerful hints Difficulties Techniques Leaderboard
How to play
Fill the 9×9 grid so that each row, each column, and each of the nine 3×3 boxes contains the digits 1–9 exactly once. Given clues are fixed. Every move should follow from the clues — guessing is not required on a well-posed puzzle, and BoringTime only serves puzzles with a unique solution.
Start with cells that have a single remaining candidate. When the easy placements run out, look for locked candidates, pairs, and larger patterns. The app’s hint system is built around those same human steps.
Photo scan
You do not have to type a newspaper puzzle by hand. On the Sudoku difficulty screen, choose scan:
Camera or gallery
Take a new photo or pick one you already have. Fit the full outer Sudoku frame in view — the thick border around the whole 9×9, not just a few boxes.
Confirm the four corners
Drag corners 1–4 so the overlay sits on the outer grid line. Pinch to zoom if the page is skewed. Tap confirm when the frame is aligned.
Read, check, play
The app reads the digits, rejects grids that are not valid Sudoku, and rejects puzzles with more than one solution. If the photo is accepted, the game starts at a difficulty that matches the grid. If reading fails, take a sharper shot of the whole border rather than cropping into the inner boxes.
Powerful hints
Hints come from a human-style solver in the HoDoKu family. They are not a computer “fill this cell” cheat. Each hint names the technique, marks the cells, rows, columns and boxes that matter, and lists the digits to place or eliminate — including the implication chain when the step is a chain.
- Named techniques from singles through pointing, pairs, fish, wings, uniqueness, colouring, X/XY-chains, nice loops, ALS, and forcing chains on the hardest packs.
- Teaching layout: you can read how the technique works, then apply it yourself. Apply writes the placement or the draft eliminations.
- Quota by cell: tapping hint reserves that empty cell. You may open the same hint again without spending another slot. A different cell uses a new reservation.
Difficulties in the app
Easy and Medium puzzles are generated on the device. Hard, Expert, Master, Extreme, and Monster come from packed libraries. Monster appears after you meet the Extreme clear requirement. Monthly leaderboard records are kept for Extreme and Monster. Replays are saved from Hard upward.
Technique catalog
The full list of named human techniques, with number-grid examples in six languages, lives on a dedicated page:
Sudoku techniques — singles, pointing, pairs, fish, wings, chains
- Singles — naked/hidden single and full house (Easy through Hard).
- Locked candidates and subsets — pointing, claiming, pairs, triples, quads (typical Expert).
- Fish and wings — X-Wing through WXYZ-Wing, uniqueness (Master / most Extreme).
- Chains and ALS — colouring, X/XY-chains, nice loops (AIC), ALS; forcing chains on Monster.