Cool game and very cool idea! I think it is also a cool educational game for a first computer science class.
I did not hear any sounds, eventhough the setting for effects is there. Maybe it simply did not work for me... What I would improve is the feedback which lines are squashed. When I squashed multiple lines I sometimes had the feeling a wrong line (just the one above the last one) was also squashed, but I think it just looked like that as a line a few lines above was squashed.
I had really fun playing it! Congrats to your innovative game!