So, in the tools area of the deck building part of this app, what is the gravity for?
It takes all the *pips* of your deck, and generic costs, and creates a motion-sensitive bubble-pool. *pips* being the colored mana symbols in the casting costs of your spells.
While it is fun to just play around with, it also gives a nice visual to the relative amount of pips you have in your deck. This can aid in determining your mana base.
Thanks!