HA. Its not turn based, though you can hit spacebar to pause the game and place blocks in the world to act as impromptu ramps and girders.
I think this game is going to be leaning more towards SP and alot of really messed up challenges you need to get through. Could be some sort of online score/time board though. Head on racing will be something left for later possibly...
Depends where it goes from here, but the gameplay right now is fun enough, and tricky enough, without another player messing it up
We will have to wait, and see.