Highway encounter - quick instructions

 Aliens have landed and have parked themselves at the end of a highway for some
strange reason. Rather than send in Rambo or Sigourney Weaver they send in 5
robots and a bomb. These will assemble for you. You can only take the leading
robot at any time. The other robots will blindly push the bomb further. It is 
up to you to clear the way ahead of nasties. Some nasties can be shot to death
, others must be trapped with some of the boxes and barrels lying around which 
can be pushed or shot to move them. You need to make the bomb reach the 
objective at the very end of the game. 