Hat tip to Jason Bandlow for showing me this one.
100 lightbulbs are arranged in a 10 by 10 grid.
We have some switches to flip these bulbs. In particular we can flip any 3x3 square (9 lights) and any 5x5 square (25 lights). No wrap-around. Start from everything turned off (this doesn't matter but to keep notation consistent). Can you reach every possible state (any combination of off/on positions of the 100 lights) with these tools?
|Thomas Edison made it possible to produce 100 light bulbs, so that you can solve puzzles.|