Bridges...
	Signs...

The red or blue material will break your bridges. Look for a way around or change the length this if this material is breaking your bridge. Destroy unused bridges so they do not get in your way. Destroy bridges as your citizens walk across them to allow them to fall onto platforms that are closer to the goal.

The signs that appear before each level reveals the level that the citizen will be holding. Those signs have helpful hints about how that level can be completed.