Sudoku
Game Overview
Sudoku is a constraint‑satisfaction number puzzle. Fill the 9×9 grid so each row, column, and 3×3 sub‑grid contains digits 1–9 exactly once.
This streamlined implementation focuses on legibility and quick interaction. Improve your solving speed with the core logic techniques below—no brute force guessing required on properly generated boards.
Controls
- Click / Tap: Select a cell.
- Number Keys (1–9): Enter a value.
- Restart: Generate a new puzzle.
Tip: Fill certain singles early to reduce branching complexity.
Core Solving Techniques
Naked Single: A cell with only one possible candidate must be that digit.
Hidden Single: A digit appears only once in the candidate set of a row/col/box—place it.
Candidate Elimination: Placing a number removes it from peers’ candidate sets.
Box-Line Interaction: If a candidate in a 3×3 box lies only in one line, eliminate that candidate from the rest of the line.
Strategy Guide
1. Scan & Seed
Pass through rows, columns, and boxes to locate obvious singles. Early momentum accelerates deduction.
2. Structure Candidates
Mentally track potential placements (pencil marks conceptually) to foresee forced resolutions.
3. Propagate Constraints
Every placement radiates constraints into its row, column, and sub‑grid. Systematic propagation prevents oversight.
Solving speed arises from disciplined elimination, not hunches. Method beats intuition over long runs.
Common Mistakes
- Guessing Early: Leads to contradiction backtracking—inefficient.
- Overlooking Hidden Singles: A frequent speed bottleneck.
- Column Neglect: Players often favor rows; balance scanning.
- Candidate Overload: Tracking too many hypotheticals without isolating certain placements.
Sudoku FAQ
Is guessing ever required?
Properly constructed puzzles are solvable with logic only; no guessing needed.
Fastest improvement tip?
Drill recognition of Naked vs Hidden Singles—they form most early game progress.
Why do I stall mid grid?
Likely missed a constrained candidate—rescan boxes carefully for unique placements.
What difficulty is this?
Baseline logic tier; advanced techniques (X-Wing, Swordfish) not required here.
Is there error checking?
This minimalist build doesn’t auto‑flag mistakes—accuracy discipline improves skill.