b0c4d837 ​

input = fill (#2.3 + 1) (fill #0 black) |> fold (λr. rect ((r.1, r.2, #2.3 + 1, r.3), grey)) #1 |> rect (#2, teal)
output = [[teal, #3, #4], [black, black, #5], [black, black, black]]
(HInt, UList (VInt, HInt, HInt), (VInt, HInt, VInt, HInt), Color, Color, Color)
(6h, {(2v, 5h, 5h), (6v, 2h, 5h), (2v, 2h, 2h)}, (5v, 3h, 5v, 4h), teal, teal, black)
(9h, {(2v, 7h, 7h), (9v, 3h, 7h), (2v, 3h, 3h)}, (6v, 4h, 8v, 6h), teal, teal, teal)
(9h, {(3v, 8h, 8h), (9v, 2h, 8h), (3v, 2h, 2h)}, (6v, 3h, 8v, 7h), teal, teal, black)
(9h, {(3v, 7h, 7h), (9v, 3h, 7h), (3v, 3h, 3h)}, (5v, 4h, 8v, 6h), teal, black, black)
(6h, {(2v, 5h, 5h), (5v, 2h, 5h), (2v, 2h, 2h)}, (3v, 3h, 4v, 4h), black, black, black)
(7h, {(3v, 6h, 6h), (7v, 2h, 6h), (3v, 2h, 2h)}, (5v, 3h, 6v, 5h), teal, black, black)
(9h, {(2v, 7h, 7h), (9v, 3h, 7h), (2v, 3h, 3h)}, (3v, 4h, 8v, 6h), ?, ?, ?)