I like the concept of the game as well as the gameplay. The tutorial was very helpful as well.
I would recommend that you play around with sound a bit more to balance it and make it a bit less sharp. The text sounds as well as the soundtrack generates this sharp beat which is irritating if you're wearing headphones (like I was).
It would also be nice if there was some sort of timer or bar which lets the player know how far they have reached in the marathon.
Overall, I'd say its a pretty solid game. Nice work!