a3f84088 ​

input = fill #0 (fill #1 #2) |> fold (fold rect) #3
output = fill #0 (fill #1 #2) |> fold (fold rect) #4
(VInt, HInt, Color, OList UList ((VInt, HInt, VInt, HInt), Color), OList UList ((VInt, HInt, VInt, HInt), Color))
(13v, 13h, black, [{((2v, 2h, 10v, 10h), grey)}, {((3v, 3h, 9v, 9h), black)}], [{((2v, 2h, 10v, 10h), grey)}, {((3v, 3h, 9v, 9h), red)}, {((4v, 4h, 8v, 8h), grey)}, {((5v, 5h, 7v, 7h), black)}])
(6v, 6h, grey, [{((2v, 2h, 5v, 5h), black)}], [{((2v, 2h, 5v, 5h), red)}, {((3v, 3h, 4v, 4h), grey)}])
(16v, 16h, black, [{((2v, 4h, 13v, 15h), grey)}, {((3v, 5h, 12v, 14h), black)}], [{((2v, 4h, 13v, 15h), grey)}, {((3v, 5h, 12v, 14h), red)}, {((4v, 6h, 11v, 13h), grey)}, {((5v, 7h, 10v, 12h), black)}, {((6v, 8h, 9v, 11h), grey)}, {((7v, 9h, 8v, 10h), red)}])
(19v, 19h, black, [{((2v, 2h, 18v, 18h), grey)}, {((3v, 3h, 17v, 17h), black)}], [{((2v, 2h, 18v, 18h), grey)}, {((3v, 3h, 17v, 17h), red)}, {((4v, 4h, 16v, 16h), grey)}, {((5v, 5h, 15v, 15h), black)}, {((6v, 6h, 14v, 14h), grey)}, {((7v, 7h, 13v, 13h), red)}, {((8v, 8h, 12v, 12h), grey)}, {((9v, 9h, 11v, 11h), black)}, {((10v, 10h, 10v, 10h), grey)}])
(30v, 30h, black, [{((2v, 2h, 26v, 26h), grey)}, {((3v, 3h, 25v, 25h), black)}], ?)