Here is a very simple example of a level where we can make the balloons 

have to go through a maze of air ducts in a building...

In this second one we can have a very simple room where the walls are full

of static and you have to keep the balloons from gravitating towards 

the side walls and popping as they are rising...

In this design we can have the balloons rising between building in a city...

And lastly we can have the balloons rising between canyon walls in a desert...