[let | MODEL [ 0.5 0.1 0 1 <range> ] |

  [let | VIEW    [ MODEL [ first round number>string ] <filter> <label-control> ]
         CONTROL [ MODEL <x-slider>                                             ] |

    <pile> 1 >>fill
      VIEW add-gadget
      CONTROL add-gadget
    "test" open-window ] ]