On the difficulty of your songs:
The game is good, I'll grant you that. The songs were good, the arrows were well timed, and the premise was fun enough that it kept me playing. But let me tell you something that none of the "Rock Out" artists seem to understand when they make a rhythm game:
You need more notes on the offbeats! In DDR when Medium goes to Hard, it's not because there are just MORE buttons to press, it's that the buttons had to be pressed FASTER, even though they remained in beat with the song. Every time an arrow hit the top, except from some minor cases where triplets and things in the songs were matched, it was on the beat. You have to use offbeats to improve the difficulty of the song, not just more notes. Thus, I found the last (Hard) song to be just as simple as the first (Easy) song, only twice as long and a bit more difficult to get a grip on the beat.
In layman's terms, for the non-musically inclined:
Instead of DA-da-DA-da, there could be DA-da-da-DA-DA-da-da-DA all taking place in the same four count. THAT'S what makes hard "Hard," not just sticking in more Da's.
Be unforgiving in your difficulty. If you make a good game, and you make it right, people who complain that they can't do well just aren't good enough. Hard NEEDS to be hard, and Easy easy. That's where the fun comes in.
