They sighted along the diagonals of the room and pressed buttons.
The snail can move up, down, and across the board and through the diagonals.
Every column, every row, and each of the two diagonals now add up to 12.
A Parallelogramme is equall to his diagonals and complements.
The best way to test for squareness is to measure the diagonals with a stick.
Crease and fold ...