992798f6 ​

input = fill #0 (fill #1 black) |> rect ((#2, #3, #2, #3), red) |> rect ((#4, #5, #4, #5), blue)
output = fill #0 (fill #1 black) |> rect ((#2, #3, #2, #3), red) |> rect ((#4, #5, #4, #5), blue) |> fold (λr. rect (r, green)) #6
(VInt, HInt, VInt, HInt, VInt, HInt, UList (VInt, HInt, VInt, HInt))
(13v, 12h, 4v, 12h, 11v, 2h, {(10v, 3h, 10v, 3h), (9v, 4h, 9v, 4h), (8v, 5h, 8v, 5h), (7v, 6h, 7v, 6h), (6v, 7h, 6v, 7h), (5v, 8h, 5v, 11h)})
(15v, 12h, 2v, 2h, 14v, 9h, {(13v, 8h, 13v, 8h), (12v, 7h, 12v, 7h), (11v, 6h, 11v, 6h), (10v, 5h, 10v, 5h), (9v, 4h, 9v, 4h), (3v, 3h, 8v, 3h)})
(15v, 16h, 2v, 7h, 13v, 4h, {(12v, 5h, 12v, 5h), (3v, 6h, 11v, 6h)})
(16v, 16h, 14v, 4h, 2v, 12h, {(9v, 5h, 13v, 5h), (8v, 6h, 8v, 6h), (7v, 7h, 7v, 7h), (6v, 8h, 6v, 8h), (5v, 9h, 5v, 9h), (4v, 10h, 4v, 10h), (3v, 11h, 3v, 11h)})
(16v, 16h, 14v, 13h, 2v, 5h, ?)