applications.collages.collageAlgebra:
{
  dark = const(0),
  light = const(1),

  tri = { filledPolygon((-1,0),(1,0),(0,sqrt(3)))<(#light + #dark)/2> },
  trii = { filledPolygon((-1,0),(1,0),(0,sqrt(3)))<1 - (#light + #dark)/2> },
  S = #tri,
  T = #tri,
  Ti = #trii,
  
  f1 = similarity((-1,0) -> (-1,0), (1,0) -> (0,0)),
  f2 = similarity((-1,0) -> (0,0), (1,0) -> (1,0)),
  f3 = similarity((-1,0) -> (-.5,sqrt(3)/2), (1,0) -> (.5,sqrt(3)/2)),
  f4 = scale(-1,-1) . use(f3),
  F = <f1,f2,f3,f4>,
  
  c1  = colourOperation(r|.5:#dark,g|.5:#light,b|.5:#dark),
  c2  = colourOperation(r|.5:#dark,g|.5:#dark,b|.5:#light),
  c3  = colourOperation(r|.5:#light,g|.5:#dark,b|.5:#dark),
  c4  = colourOperation(r|.5:#dark,g|.5:#dark,b|.5:#dark),

  c1i  = colourOperation(r|.5:#light,g|.5:#dark,b|.5:#light),
  c2i  = colourOperation(r|.5:#light,g|.5:#light,b|.5:#dark),
  c3i  = colourOperation(r|.5:#dark,g|.5:#light,b|.5:#light),
  c4i  = colourOperation(r|.5:#light,g|.5:#light,b|.5:#light)
}
