Two-colored tiling(s) by science writer Barry Cipra presented at MOSAIC 2000

This Pc'4 tiling has also appeared in page 286 of the October 1999 issue of the Mathematics Magazine. Rotate each square in every other SW-NE diagonal, including those containing all-black and all-white squares, by 90 degrees clockwise, and all other squares by 90 degrees counterclockwise, and you get the Pc'4mm tiling to the left of it; repeat the process rotating each square in the opposite direction this time, reversing colors in all clockwise rotated squares, and you get the Pc'4mm tiling on the cover!