fn cube = (length, center) => {
  l = length / 2
  x = center[0]
  y = center[1]
  p0 = [-l + x, -l + y]
  p1 = [-l + x, l + y]
  p2 = [l + x, l + y]
  p3 = [l + x, -l + y]

  return startSketchAt(p0)
  |> lineTo(p1, %)
  |> lineTo(p2, %)
  |> lineTo(p3, %)
  |> lineTo(p0, %)
  |> close(%)
  |> extrude(length, %)
}

myCube = cube(40, [0, 0])