mujoco

<mujoco>
  <option>
    <flag island="enable"/>
  </option>

  <default>
    <joint type="slide" axis="1 0 0" damping="3" frictionloss=".1"/>
    <geom type="cylinder" size=".07 .1" zaxis="0 1 0"/>
    <site size=".015" rgba="1 0 0 1"/>
  </default>

  <worldbody>
    <site name="anchor" pos="0 0 1"/>

    <body pos="0 0 .75">
      <joint stiffness="10"/>
      <geom name="0"/>
    </body>
    <site name="side0" pos=".15 0 .75" rgba="0 0 1 1"/>

    <site name="01" pos="0 0 .625"/>

    <body pos="0 0 .5">
      <joint stiffness="30"/>
      <geom name="1"/>
    </body>
    <site name="side1" pos="-.15 0 .5" rgba="0 0 1 1"/>

    <site name="12" pos="0 0 .375"/>

    <body pos="0 0 .25">
      <joint stiffness="100"/>
      <geom name="2"/>
    </body>
    <site name="side2" pos=".15 0 .25" rgba="0 0 1 1"/>

    <body>
      <freejoint/>
      <site name="box" pos="0 0 .1"/>
      <geom type="box" size=".1 .1 .1"/>
    </body>
  </worldbody>

  <tendon>
    <spatial limited="true" range="0 1.05" rgba="0 1 0 1" width=".005">
      <site site="anchor"/>
      <geom geom="0" sidesite="side0"/>
      <site site="01"/>
      <geom geom="1" sidesite="side1"/>
      <site site="12"/>
      <geom geom="2" sidesite="side2"/>
      <site site="box"/>
    </spatial>
  </tendon>
</mujoco>