fn cube = (pos, scale) => {
  const sg = startSketchOn('XY')
    |> startProfileAt(pos, %)
    |> line(end = [0, scale])
    |> line(end = [scale, 0])
    |> line(end = [0, -scale])

  return sg
}
const part001 = cube([0,0], 20)
    |> close()
    |> extrude(length = 20)

const part002 = startSketchOn(part001, "start")
  |> startProfileAt([0, 0], %)
  |> line(end = [0, 10])
  |> line(end = [10, 0])
  |> line(end = [0, -10])
  |> close()
  |> extrude(length = 5)
