📖 Number Cell

Akari Puzzle Glossary — All Terms

Number Cell — A number cell is a black cell in an Akari puzzle that displays a digit from 0 to 4. This number tells you exactly how many light bulbs (or cats, on GridPaw) are placed in the four orthogonally adjacent cells — up, down, left, and right.

⚙️ How It Works

Number cells are the primary source of logical constraints in every Akari puzzle. A "0" means none of its neighbors can hold a bulb. A "4" means all four neighbors must contain one. A "2" means exactly two of the four adjacent cells have bulbs. The number never counts diagonal neighbors — only the four orthogonal directions.

⚖️ Pros & Cons

✅ Advantages

  • Provide clear, unambiguous constraints that drive solving forward
  • Create cascading deductions — solving one number cell often reveals the answer to others
  • Make puzzles solvable through pure logic without guessing

⚠️ Trade-offs

  • On sparse grids, too few number cells can make puzzles feel under-constrained
  • Beginners sometimes confuse orthogonal (4 directions) with diagonal (8 directions)

🎯 Who Should Use It?

Every Akari player needs to understand number cells. They are the foundation of all solving techniques. Start by scanning for "0" and "4" cells — they give the most information with the least effort.

🚀 Step-by-Step Guide

1

Find "0" cells

A "0" cell means none of its four neighbors can hold a bulb. Mark all four adjacent cells with X marks immediately.

2

Find "4" cells

A "4" cell means all four neighbors must be bulbs. Place cats in all four adjacent cells right away.

3

Count remaining spaces

For "2" or "3" cells, count how many adjacent cells are still available. If a "3" cell has one neighbor already blocked, the other three must all be bulbs.

4

Propagate consequences

After each placement, check what new constraints are triggered. Newly placed bulbs illuminate rows and columns, which may force or eliminate other placements.

❓ FAQ

What does a "0" mean in an Akari puzzle?

A "0" means none of its four adjacent cells can contain a light bulb. It immediately eliminates four positions, which often triggers a chain of further deductions.

Do number cells count diagonal neighbors?

No. Number cells only count orthogonal neighbors — up, down, left, and right. Diagonal cells are not counted.

Can a number cell be wrong?

No. Number cells are fixed clues placed by the puzzle designer. They are always correct. If your bulbs conflict with a number cell, the error is in your placement.

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