- Click on empty cells to place light bulbs
- Bulbs illuminate their row and column until blocked by black cells
- Numbered black cells show how many bulbs must surround them (0-4)
- No two bulbs can illuminate each other
- Light up all white cells to win!
Light Up: Illuminate the Grid
Place bulbs to light up every cell without crossing their beams. A pure logic challenge governed by numbers.
How to Play Light Up
The goal of Light Up (also known as Akari) is to place light bulbs on the grid so that every empty white square is illuminated.
Bulbs shine light horizontally and vertically until it hits a black wall or the edge of the grid. Every white cell must be lit by at least one bulb.
Some black walls contain numbers from 0 to 4. This number indicates exactly how many bulbs must be placed adjacent to that wall (horizontally or vertically, not diagonally).
Two light bulbs can never shine on each other. You cannot place a bulb in a cell that is already illuminated by another bulb.
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→What is Light Up (Akari)?
Light Up, also known under its original Japanese name Akari, is a logic puzzle created by Nikoli. It is played on a rectangular grid of white and black cells. The objective is to place light bulbs in white cells such that the entire grid is illuminated.
A bulb illuminates all cells in its row and column unless its light is blocked by a black cell. What makes the game challenging are the numbered black cells, which act as strict constraints, and the fundamental rule that no two bulbs may shine on each other.
Like Sudoku or Minesweeper, Light Up requires no arithmetic, only pure deduction. It rewards forward-thinking and careful analysis of spaces.
History of Light Up
Light Up was invented by Nikoli, the famous Japanese puzzle publisher known for popularizing Sudoku. It first appeared in Nikoli's puzzle magazine in 2001 under the name Akari (which translates to 'light' or 'illumination').
It quickly became a favorite among logic puzzle enthusiasts due to its simple rules but deep emergent strategies. Today, it is a staple in logic puzzle collections worldwide.
Difficulty Levels
Light Up scales beautifully from small, breezy grids to massive, intricate challenges.
~2–5 min
Perfect for learning the rules. High density of clues and numbers helps you find placements quickly.
~5–12 min
Requires combining multiple clues. You will need to start marking cells where bulbs definitely cannot go.
~10–25 min
Features sparse clues and large open areas. Demands advanced strategies and looking several steps ahead to avoid dead ends.
How to Solve Light Up Efficiently
Start with 4s and diagonals
A '4' means all four adjacent cells must have bulbs. Place them immediately. Also look at diagonal adjacent black cells; they often force specific placements.
Mark empty spaces
Use the right-click (or dot tool) to mark cells where a bulb definitely cannot go. This is crucial for visualizing where remaining bulbs must be placed.
Satisfy the 0s
A '0' means no bulbs can touch it. Instantly mark all 4 adjacent cells as empty (dots) to prevent accidental placements.
Check unlit corners
If a cell is unlit and has only one possible adjacent cell that can illuminate it, a bulb must go there.
Tips & Tricks
Cornering numbers
A '3' against an edge or a '2' in a corner functions identically to a '4' in the center: all available adjacent cells must be bulbs.
Chain reactions
Placing a bulb illuminates a long line. Immediately check if this new light fulfills the requirements of any other areas or forces a bulb into a specific spot.
Look for trapped cells
Sometimes an unlit cell is surrounded by illuminated cells or walls. If it's the only way to light itself, the bulb goes exactly there.
Why Play Light Up?
Light Up is a brilliant exercise in spatial reasoning and constraint satisfaction.
Visual logic
Unlike number-heavy puzzles, Light Up is highly visual. You instantly see the impact of your moves as beams of light shoot across the board.
No guessing required
Every Light Up puzzle can be solved with pure logic. You never have to guess.
Flow state
The immediate feedback of lighting up rows and columns creates a highly satisfying flow state as the board rapidly fills up.
Light Up vs Other Logic Puzzles
If you enjoy illuminating grids, see how Light Up compares to our other favorites.
Light Up vs Minesweeper
ExploreSimilarities: Both use numbered clues on a grid to deduce the locations of hidden items (bulbs or mines).
Differences: Minesweeper clues count all 8 surrounding cells and involve avoiding mines. Light Up clues count only 4 orthogonal cells, and you are actively placing items to 'fill' the board with light.
Verdict: If you prefer spatial mechanics and line-of-sight logic over purely adjacent counting, Light Up is for you.
Light Up vs Sudoku
ExploreSimilarities: Both are pure logic puzzles with a single unique solution.
Differences: Sudoku uses abstract symbols (numbers) and overlapping sets (rows, columns, boxes). Light Up uses spatial geometry and line-of-sight.
Verdict: Play Light Up when you want a visual, spatial puzzle rather than a numeric one.