mujoco

<mujoco>
  <option gravity="1 0 0">
    <flag island="enable"/>
  </option>

  <default>
    <joint type="slide" axis="1 0 0" damping="10"/>
    <geom size=".1"/>
  </default>

  <worldbody>
    <body>
      <geom type="box" size=".05 .1 .1"/>
    </body>
    <body pos=".25 0 0">
      <joint/>
      <geom/>
    </body>
    <body pos=".5 0 0">
      <joint/>
      <geom/>
    </body>
    <body pos=".75 0 0">
      <joint/>
      <geom/>
    </body>
    <body pos="1 0 0">
      <joint/>
      <geom/>
    </body>
    <body pos="1.25 0 0">
      <geom type="box" size=".05 .1 .1"/>
    </body>
  </worldbody>
</mujoco>