I like the katamari effect, and how the added cars weighed you down. I ran into some bugs, however, after losing on the third level and restarting. The counter persisted from the last level, so when level one restarted, it had 1 cars left despite there being 2 in the scene. After hitting both those cars, the counter was at -1, and the level did not end. The cars were added to an invisible stack that also persisted from the failed third level, the clock counted down and I failed it. By the third run, the strain of phantom cars was debilitating, and by the fourth, the suspension gave out altogether.
Anyway, probably just some values need resetting. Fun idea, and great work on your game!