Race game - suggestion needed

So, I got this Collision Detection Kit thing (http://coreyoneil.com/portfolio/index.php?project=5) and merged it with my keyboard controlled car.

Here you can see the result: http://www.esnips.com/doc/fea0306c-4d28-4ed7-afca-45fbd2e3edfe/Corrida---hardcoded
(Arrow keys to move)

When I realized the track creation process was incredibly easy, I made a little drawing game out of it: http://www.esnips.com/doc/1d6987a4-09ae-46ce-878e-6889ed18461b/Corrida---drawing
(hold and drag to draw, click the car to clear. Arrow keys to move)

So it’s kinda a line rider with a racing car.

What I want now are suggestions. Let your gamer side speak. What can be done with this thing? Same-keyboard multiplayer? Track sharing app? Racing game (with highscores, upgrades, race and drift modes and everything) with track editor?

Also, I’ll gladly release the source once I find a use for this and organize the code better, or if anyone is really interested.