N currently consists of 500 levels which are divided into episodes. The episodes are then divided into columns, which are sets of 10 episodes. There are currently ten columns in the game. The 80s column is unique because it is the only one with levels not created by Metanet Software. Instead, it contains levels created by other players.
You unlock a new flavour for your ninja at the end of each column, as a reward for your hard work and effort.
Including NReality, there are 1000 levels divided into 20 columns.