This is great fun. With a few glaring flaws...
Looks great, I haven't really seen anything that has that exact art style before. Loads of juice, good feeling of speed.
Music is waaay too short, and was annoying me after a few laps. I have no idea how you stood that for 4 days of dev!
The car goes just that little bit too fast for my tastes. I keep crashing a lot, but it's super satisfying when I managed to string a few curves together. I like the simplicity of a single button to control it. I don't know how you can possibly use the speed up thing without instantly crashing however.
You can turn the car right round in places, but since you can only turn left, you can't actually drive very far. I never actually got permanently stuck though.
Pretty amazing for 4 days! Congrats!