Juggling just means that you have 2 'exits' in your maze. 2 parts where creeps can go out of your maze. The trick is too close off the exit where they are getting to and they will go to the other exit. Just sell the tower you placed before and place it on the exit where the creeps are getting to now. Just do this infinitine and the ground creeps will never leave your maze if you are good.
Most people use 3-way-mazes for juggling, it's easy, always keep one exit closed, open and half open. The sell timer does increase, but has a cap.
0 is to deselect a tower, but many people wouldn't use it for that.
And i got the badge.
It requires juggling though, sorry for all you juggling haterz...
http://youtube.com/watch?v=5RxFUQ_dlaw
The dark creeps have a set 15 armor meaning that they resist all hits that do less than 15 damage. They also have another armor that is based on level / 2. So if you have a level 40 dark wave, they will resist everything that does less than 20 damage.
The 100 is not possible without juggling, 10k is though. It requires lagging though, and only one person has achieved that goal so far:
[url]http://youtube.com/watch?v=nO1h7b_ojeA[/url]