ba97ae07 ​

let bg: (Int, Int)
let l1: (Bool, Int, Int, Color)
let l2: (Bool, Int, Int, Color)

let input = fill (bg.1) (fill (bg.2) black)
  |> fold (λ(f, a, b, c). rect (if f (a, 1, b, -1) (1, a, -1, b), c)) [l1, l2]

let output = fill (bg.1) (fill (bg.2) black)
  |> fold (λ(f, a, b, c). rect (if f (a, 1, b, -1) (1, a, -1, b), c)) [l2, l1]