Play Light Up Online
Place lamps so every dark square is lit and no lamp sees another.
How to Play Light Up
Modes: Classic · Daily
Place lamps on empty squares to light the board.
A lamp lights its whole row and column until a wall blocks it.
Numbered walls tell you exactly how many lamps sit beside them.
Fill every empty square with light — and never let two lamps meet.
Rules
No two lamps may shine on each other.
A wall with a number 0–4 must touch exactly that many lamps.
Every empty cell must be lit by at least one lamp.
Scoring
| Solved | light the whole grid |
| Time | fastest solve wins |
History & Origins of Light Up
Light Up belongs to the family of logic puzzles that Japanese puzzle magazines popularised from the 1980s onward, the same Nikoli-style tradition that later gave the world dozens of grid deduction formats. In Japan the game is known as Akari, and its premise is easy to state: switch on lamps so that every white square glows while no two lamps ever face each other across an open line.
Part of the appeal is visual. Each lamp paints a stripe of light across its row and column until a black wall stops it, so the board slowly brightens as you reason, and dark pockets instantly reveal where a lamp is still missing. Because numbered walls count only the lamps touching their four sides, solvers juggle two constraints at once: lighting every cell while keeping each number honest.
The ThinkyPlay version turns Akari into a polished daily habit. Every board is generated fresh with one guaranteed solution, Easy boards run 7×7 while Medium and Hard grow to a denser 10×10, and the Daily Light Up hands everyone the same puzzle to race, with a running best time saved per difficulty.
Common Mistakes to Avoid
- Placing a second lamp in the same unbroken row or column as an existing one: when no wall separates them the two see each other and both are flagged red.
- Forgetting that a numbered wall counts only the lamps directly above, below, left or right of it, so a lamp placed diagonally never satisfies the number.
- Treating an unnumbered black cell as harmless, when every black cell still blocks light and the unlit white pocket behind it needs its own lamp on that side.
- Rushing past walls marked 0, which are gifts: all four neighbouring cells must stay empty and usually unlock the first safe deductions of the board.
Tips & Strategy
Zero walls are gifts — leave all four sides empty.
Corners and edges force lamps next to high-numbered walls.
When a square can only be lit by one spot, put a lamp there.
Frequently Asked Questions
- Is Light Up free to play?
- Yes — Light Up on ThinkyPlay is free, with no download and no sign-up.
- How do lamps light squares?
- Each lamp lights every cell in its row and column until a wall interrupts the beam.
- Is there a daily puzzle?
- Yes — the Daily Light Up gives everyone the same board each day.
- Do black cells without numbers still stop light?
- Yes. Every black cell is a wall that blocks a lamp beam, whether or not it carries a number. Unnumbered walls give no clue, but they matter because they split the board into separate corridors that each need their own lamp.
- Why do two lamps light up red together?
- That is the no-two-lamps-may-see-each-other rule firing: with no wall between them, the two stand in the same row or column and their beams meet. Remove or move one before the grid will count as solved.
- What actually changes between Easy, Medium and Hard?
- Easy uses a 7×7 board, while Medium and Hard play on 10×10 grids. Hard packs in more black walls and fewer numbered clues, which fragments the board into more dead ends and forces longer chains of deduction.