I put the word custom in quotation marks because although you do get to create your own racer, there isn't really a full character creation system in place. (cogconnected.com)
The game ships with a full level creation system in place, and it is powerful. (snackbar-games.com)
To help the process along, the company released a 28 - page document for formatting in order to help authors get through the web - based creation system. (macnn.com)