This puzzle is part of the Puzzling StackExchange Advent Calendar 2021. The accepted answer to this question will be awarded a bounty worth 50 reputation.

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empty Tentai Show grid

Divide the grid into "rooms" among grid lines so that each room is 180° rotationally symmetrical and contains exactly one white or black circle, located in its centre. In the end, shade all rooms with a black circle in them to form a picture.

Paraphrased from original rules on Nikoli

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    $\begingroup$ For interested solvers, a puzz.link. No warranty expressed or implied, but I think I got it right. $\endgroup$ Dec 2 '21 at 21:02

Sorry for the formatting; I can try to clean it up and provide steps with a bit more time if desired.

full puzzle solved

At the very least, I'll point out the main "hurdle" point I faced. After initial markings, focus on the marked cell:

enter image description here

The wall blocks most points from being centers for regions containing the starred cell.


I solved the problem using the UI which Jeremy Dover linked to in the comments.

In my case, the main hurdle was when I got to this point:

Main hurdle

I kept on staring at the cell highlighted in yellow, and I could not figure out a way to make a symmetrical room that includes it and has a star in the center.

Eventually, I realized that the only possibility is a shape that reaches all the way to the top of the grid.

After I filled that in, everything else eventually fell into place.

This is what the solved puzzle looks like:

Solved puzzle


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