e76a88a6 ​

input = fill 10v (fill 10h black) |> fold (fold rect) #0
output = fill 10v (fill 10h black) |> fold (fold rect) #1
(OList UList ((VInt, HInt, VInt, HInt), Color), OList UList ((VInt, HInt, VInt, HInt), Color))
([{((3v, 2h, 4v, 4h), yellow)}, {((2v, 2h, 2v, 4h), red), ((2v, 2h, 3v, 2h), red), ((8v, 3h, 10v, 5h), grey), ((5v, 7h, 7v, 9h), grey)}], [{((9v, 3h, 10v, 5h), yellow), ((6v, 7h, 7v, 9h), yellow), ((3v, 2h, 4v, 4h), yellow)}, {((8v, 3h, 8v, 5h), red), ((8v, 3h, 9v, 3h), red), ((5v, 7h, 5v, 9h), red), ((5v, 7h, 6v, 7h), red), ((2v, 2h, 2v, 4h), red), ((2v, 2h, 3v, 2h), red)}])
([{((3v, 3h, 4v, 5h), teal)}, {((2v, 2h, 3v, 5h), fuschia)}, {((4v, 3h, 4v, 5h), teal), ((3v, 2h, 3v, 3h), teal), ((1v, 7h, 3v, 10h), grey), ((6v, 5h, 8v, 8h), grey), ((4v, 2h, 4v, 2h), fuschia)}], [{((2v, 8h, 3v, 10h), teal), ((7v, 6h, 8v, 8h), teal), ((3v, 3h, 4v, 5h), teal)}, {((1v, 7h, 2v, 10h), fuschia), ((6v, 5h, 7v, 8h), fuschia), ((2v, 2h, 3v, 5h), fuschia)}, {((3v, 8h, 3v, 10h), teal), ((2v, 7h, 2v, 8h), teal), ((8v, 6h, 8v, 8h), teal), ((7v, 5h, 7v, 6h), teal), ((4v, 3h, 4v, 5h), teal), ((3v, 2h, 3v, 3h), teal), ((8v, 5h, 8v, 5h), fuschia), ((4v, 2h, 4v, 2h), fuschia), ((3v, 7h, 3v, 7h), fuschia)}])
([{((1v, 2h, 3v, 4h), yellow)}, {((3v, 4h, 4v, 4h), blue), ((4v, 2h, 4v, 4h), blue), ((2v, 2h, 4v, 2h), blue), ((7v, 8h, 10v, 10h), grey), ((6v, 3h, 9v, 5h), grey), ((2v, 7h, 5v, 9h), grey)}], ?)