A great idea and a very fun game!
I like the music (and how there's more than 1 track), but the motorbike engine sound could be improved, maybe change the pitch based on your speed?
Graphics are veery nice, it really shows that two people worked on this game.
I even like the implementation of the theme, because when you're low on time, and you finally find an "order" to pickup to increase your time, and it's not real? Causes a lot of panic, which in my opinion is pretty neat.
Also, I would make the invisible walls more clear, because right now you can't really tell where you can go.
Really, great job!