Problem solution

The problem I posted a couple of days ago:

An 8 by 8 square is painted white. We are allowed to choose any rectangle consisting of 3 of the 64 (1 by 1) squares and paint each of the 3 squares in the opposite colour (the white ones black, the black ones white). Is it possible to paint the entire square black by means of such operations?

( Solution below the cut. )

A plan so cunning...

Yesterday our D&D group actually did something competent!

( Read more... )