Fun game. It's actually hardest in the beginning. After you reach a certain point between the survivors increasing your health and eventually maxing out your upgrades it gets an autopilot mode where your turrets kill everything for you. I don't think I actually did anything the last 5 or 6 waves. Should work to make the difficulty scale through all 20 waves.
$5000 on the last level. Fun but too short. It would interesting to have different weights or test for max weight to see who could build the strongest or strongest/cheapest bridge.
 "Candy Conveyor"){kind=icon}
 "Try to Survive"){kind=icon}
 "Blocks With Letters On 3"){kind=icon}
 "FWG Bridge"){kind=icon}