be94b721 ​

let bg: (Int, Int)
let ps: OList (Color, (Int, Int), (Int, Int), OList (Int, Int))

let input = fill (bg.1) (fill (bg.2) black)
  |> fold (λ(c, l, bg, ps). fold (λp. point (p + l) c) ps) ps

let output = ps
  |> sort (λ(c, l, bg, ps). -len ps)
  |> dot 1
  |> (λ(c, l, bg, ps). fill (bg.1) (fill (bg.2) black)
    |> fold (λp. point p c) ps)