Here's a quick Monday morning puzzle.
Quick?? I spent several hours on it, not being able to come with anything better then this:
<Reveal this spoiler or all in this thread>
It's a bit randomized, but usually runs under 2 seconds on my machine. Run it with a filename as an argument to check the solution saved in the file.
Update: Removed forgotten debugging line.
Update2: Readmore changed to spoiler.

In reply to Re: Lights out puzzle by choroba
in thread Lights out puzzle by ambrus

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