Expansions
Mattel released six energy cars that each came with a CD and a race for each CD collected. When all were collected a player would be awarded with a special track build and they could race on that track.
The developers intended to release a track editor for the game. This would allow players to build their own race track and race with people on their friends list. However this feature only appeared in a single player form on the site, the more complex of a track the user created the more credits they could earn.
Read more about this topic: Planet Hot Wheels