XP, or Experience Points, are gained only when users are logged into a Facebook or a guest account. XP that is gained will contribute to reaching higher levels and acquiring new veteran skins. The amount of XP required to advance to the next level increases every level. For example, level one requires very little XP compared to level 99.
THIS INFORMATION IS COLLECTED FROM MANY TESTS, THE WAY THAT THE XP MECHANICS FULLY WORK HAS NOT BEEN RELEASED.
The amount of XP that you earn per game depends on two things:
The more mass you have the more XP you earn per second. If you have 500 mass you will generate more XP per second than if you have 250 mass. If you are twice as big you only get about 30-40% more XP.
The more you split the more XP you gain per cell. Let us say for example you have a cell with 500 mass, you will gain double the XP if you have two 250 cells.