Nice game
OK, HUGE piece of advice here: You've got some great music to go along with this game, it fits perfectly; now make the game block move at the same pace the music does. I want to see that little block moving with the beat! It would pick up the pace of the game a lot, and people won't get bored after only 20 levels. Plus, it's more mentally appealing to have it moving with the beat.
I like the fact that you can pick up where you left off, I might go back and play it some more later. I think the music is simple enough that you could make it repeat without stopping, might make the loop a little less noticeable. It does get a bit boring after 20 levels due to the rather slow pace of the block. Also, if I hold down a direction key, the game lags up a bit.