This is a nice little game! I think something that could add just a tad bit more to the player experience would be the line constantly speeding up as the player does better and better. But great work here!
I tried to add three different difficulties to choose from in the menu but couldn't make it work, cause lack of experience, and with more challenging choice, add a multiplier to the score. If I will keep working on it I could do something like you said :)
