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Light Up

Place light bulbs in the grid so that every white square is illuminated. Light bulbs illuminate all squares they can see horizontally and vertically. They are blocked by black squares. Light bulbs are not allowed to see each other. Number clues in black squares tell you how many light bulbs there are in the 4 squares touching it.

Example

There can't be any light bulbs around the 0 in row 1. The square in the left top corner can now only be illuminated by a light bulb in the first square of row 2. The square in the right top corner can now only be illuminated by placing a light bulb on it.

Now there's one lightbulb next to the 1 in row 2, so there can't be a lightbulb under it. Now the square in the right bottom corner can only be illuminated by placing a light bulb on it.

There can't be a light bulb on the second square of row 3 as there wouldn't be room to place a second light bulb around the 2 in row 4. This light bulb would then see the light bulb in row 3, which isn't allowed. Thus the second light bulb next to the 2 in row 3 has to be below it. Now we can place the final light bulb above the 2 in row 4 and the puzzle is done.

Background

This genre was invented by Nikoli and is also known by the name Akari.


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