[mrmummert]

Just had this idea....some sort of swinging bridge...similar to a rope bridge.
basically a suspended platform the size of a defense bottom about a inch or so high off the defense base. each corner would have a rope (or chain) attached to a post holding the this up. As you drive across it could swing back and forth. If a robot sat on it then took off the base would tend to swing out from under the robot. Driving onto it too fast would make it difficult to drive across.