Even the two semicircular "squares" at the center of the board have four sides and four corners. These two "squares" share two sides and three corners in common. The corner between them which lies at the very center of the board is the singularity from which this chess variation takes its name.
This leads to some long-distance moves which are anything but straight as we think of straight. Notice how the rook's move can take it looping around the center of the board, and right back like a boomerang to the same side of the board it started from.