Light Up
Play Light Up free online: place light bulbs to illuminate the whole grid while satisfying numbered wall constraints. A bright logic puzzle with Retro Coins.
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How it works
Play, earn points and Retro Coins: the shared currency across every RetroPlayNow game. Unlock badges and climb the leaderboard! Your progress is saved automatically on this device.
Light Up, also known as Akari, is a puzzle of illumination and shadow. A grid contains black walls and white rooms. Your task is to place light bulbs in white cells such that every white cell is illuminated — either containing a bulb or being in the line of sight of one (horizontally or vertically, until blocked by a wall).
Two constraints make the puzzle challenging. First, no two bulbs may illuminate each other — if two bulbs are in the same row or column with no wall between them, they conflict. Second, numbered black cells (0-4) indicate exactly how many bulbs must be placed in the four orthogonally adjacent cells.
The solving logic is deeply satisfying. A 4 surrounded by four white cells forces all four to have bulbs. A 0 forces all adjacent cells to be empty. A 3 next to a wall (with only three adjacent white cells) forces all three. From these forced moves, the rest of the puzzle unfolds through elimination.
Our RetroPlayNow version features puzzles at multiple sizes, a tap-to-place bulb interface, real-time conflict highlighting (bulbs that shine on each other glow red), and a satisfying light-spread animation when you solve each puzzle. Every completed puzzle earns Retro Coins.
How to play Light Up
- Illuminate every white cell. Place bulbs so that every white cell either contains a bulb or is lit by one horizontally or vertically (walls block light).
- No conflicting bulbs. Two bulbs cannot illuminate each other. If they share a line of sight with no wall between them, that is a conflict.
- Satisfy numbered walls. Each numbered black cell must have exactly that many bulbs in its four orthogonally adjacent cells.
- Start with forced cells. A 4 forces all four neighbors to have bulbs. A 0 forces all neighbors empty. A 3 against a wall forces its three open neighbors.
- Earn Retro Coins. Complete puzzles to score points based on size and solving time. Faster solutions earn more Retro Coins.
