HINT: On levels where you are building above ground (as opposed to above a pit) such as level 13 you can just stick steel pillars into the ground and they will hold up the bridge ;-)
my opponent left the computer but didn't forfeit so I had to wait for the timer to run out every turn and he just passed and rested. There should be a declare victory button where the other player has 30 seconds to decline so that people can't just do this. So that it is not abused make it so that you can only use it twice per game or something.