Algodoo

You should explain either in the scene or in the scene description what are the control keys that make the bridge go up and down (arrow keys are the most common keys for controlling movement). Without those details other people won't be able to figure out how to make the bridge go up and down.

There is an old lift bridge not far from me that spans the width of the Saint Croix River between Wisconsin and Minnesota. Over the past 20 years the traffic across the river has become so dense that authorities had to build other modern bridges across that river that bypass the old lift bride!