Note: This page is taken from

N currently consists of 600 levels which are divided into episodes. The episodes are then divided into columns, which are sets of 10 episodes. There are currently twelve columns in the game. The a+b columns are unique, because they're the only ones with levels not created by Metanet Software. Instead, they contain levels created by other users.

The player unlocks a new flavour for their ninja at the end of each column, as a reward for their hard work and effort.