Fairly fun once I figured out I had to change direction before the turns and not at them. I think more and better levels would have been fun, and maybe don't let the player crash too many times into cars. There doesn't seem to be music, but at least there's sound effects for picking up stuff. I'm not sure I like how there-and-back is used (I mean, going back to the start of each level after collecting stuff gets boring after a while if the levels don't have something that makes the trip "back" significantly different from the trip "there"), but at least the theme is there. And I like the variety of cars in the second level.
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If you can make the notes fade in rather than start at full volume immediately, that might get rid of the popping. And if you stop them without fading out, that too could cause popping. For my own game I decided to play music on real instruments and edit the recordings to remove some silence, but without cutting inside notes. So on the guitar track I only cut at the very start and end (on string instruments the notes tend to overlap, and I didn't have any too long silence inside the piece that I wanted to cut out), and I think I added a fade effect to make the last note fade slightly faster than it did when I recorded it.