code: func CheckerColor(colorA color.Color, colorB color.Color, size uint) ColorFunc {
  	return func(n int, x int, y int, maxN int, maxX int, maxY int) color.Color {
  		if ((uint(x)/size)+(uint(y)/size))%2 == 0 {
  			return colorA
  		}
  
  		return colorB
  	}
  }
docs: // CheckerColor generates a ColorFunc which produces a checkerboard pattern,
  // using the two input colors.  Each square is drawn to the size specified by
  // the size parameter.