startshape curve1(0.95…0.99, 0±5)

shape curve1(shrink, turn)
{
  SQUARE[]
  curve2(=)[[y 0.5 s shrink r turn y 0.5]]
}

shape curve2(shrink, turn)
{
  SQUARE[]
  curve1(=)[[y 0.5 s shrink r turn y 0.5]]
}

