applications.collages.gridAlgebra:
( 3,
  {
    F1 = 0ab-2ba-4ab,
    F2 = 0ab-1ba-2ab,
    F3 = 0ab-1ab-2ba,
    G = 0ab-4ab-8ab,
    S += { filledPolygon((-17,-17),(0,0),(17,-17))[.5,.5,.5] },
    D += { filledPolygon((-17,-17),(17,17),(17,-17))[.5,.5,.5] }
  }
)
