sentences:  To get these parts players could buy specially marked Hot Wheels cars that came with a code that upon entering it into the site, would unlock either items for the player to use or the car itself to use in some of the website's games.Users could race and play mini-games to earn credits, the currency of Planet Hot Wheels, and purchase items and cars with them.Mattel released six "energy" branded cars, based on the six weapon energy types usable in the main game types of "Planet Hot Wheels" (Electrical, Cyber, Particle, Protonic, Geothermal, and Chemical) that each came with a CD and a level from Stunt Track Driver 2 for each CD collected.