🏮 Light Up
12 playsLight Up
Place lamps until every white square is lit, with no two lamps ever shining on each other.
About Light Up
Light Up — Akari, in its native Japan — is a puzzle of rooms and corridors. Each lamp lights its own square and throws light along its row and column until a black wall stops it. The task is to light every white square in the grid, but no two lamps may see each other along an unbroken line, and a wall carrying a number must have exactly that many lamps touching its four sides. The numbered walls are where the solving begins: a 4 is settled at once, a 0 rules out its neighbours, and every lamp placed puts a whole cross of squares beyond use for the next. Grids come in three sizes, from Easy at seven by seven through Medium at ten to Hard at twelve, each generated fresh with exactly one solution. Crosses mark the squares you have ruled out, and a hint will correct a mistake or reveal a lamp, at the cost of twenty seconds.
How to Play
Tap a white square to place a bulb, tap again for a cross marking it empty, and once more to clear it. A bulb lights every square in its row and column until a wall blocks it. No two bulbs may light each other, and a numbered wall must touch exactly that many bulbs. Solve when every white square is lit and every number is satisfied. Easy 7×7, Medium 10×10 or Hard 12×12; hints add 20 seconds, and faster solves score more.
💡 Tips & Strategy
Begin with the numbered walls that leave no choice. A 4 must have a bulb on every side, a 3 against the edge of the grid or another wall must use all three of its open sides, and a 0 forbids bulbs on all four of its neighbours, so mark those squares with crosses at once. Each bulb you place lights a whole cross of squares in its row and column, and every lit square becomes a square where no further bulb may go — the deductions spread quickly from there.
Then look for squares that only one bulb could light. An unlit white square must eventually be lit, and often only one or two squares in its row and column can see it at all; if only one of those is still allowed to hold a bulb, that is where the bulb goes. This is the most useful idea in the puzzle and solves most of what the numbered walls leave behind, especially in the corridors and pockets that a wall shuts off from the rest of the grid.
Combine the two ideas around the numbers. A 2 with three open sides, one of which is already lit or crossed, must take bulbs on the other two; a 3 forbids bulbs on all four of its diagonal squares, because a bulb there would light two of its sides at once and leave room for only two bulbs. Diagonal pairs of numbers often work together in this way, and a careful look at the two walls side by side frequently settles a square neither could settle alone.
Use crosses generously, since they record what you have already ruled out and make the next deduction easier to see. Every puzzle has exactly one solution, so a clash between two bulbs or a number turned red means a wrong step, not a trick of the grid. Hints will correct a mistake or reveal a bulb, but each adds twenty seconds, and faster solves score more.