Kudos for the artists. The 3D models look pretty good if indeed they’ve been made in only 3 days.
The car mechanics however are, as you mention, indeed very buggy. So much so that the game just doesn’t work out because of it. Also, I believe it lacks a satisfactory win state.
For a game with such a cartoony ambience, I’d sugest increasing the battery time each cell gives you, because as it stands right now I think the difficulty curve is initially very steep.