Thanks for trying it! I've beaten each level separately but I have NOT beat all of them in sequence recently (like, since enemies were added!) Adding in tile decorators -- fences or cambered edges to the 'hallways' -- was a feature that didn't make the cut but I might add in this week.
The tricky thing to balance with, say, doubling the size of the blocks is that's equivalent to halving the speed of the car. I think improving the controls and adding some affordances like those tile decorators would address some of the needless challenge.