Great idea, horrid execution
While the theory behind the game is sound, it has several flaws that will prevent it from reaching any heights beyond "notable flash game".
First and foremost, the mechanism for adding a new song. Simply pressing buttons while the song plays is a terrible idea for the following reasons:
1) People have input lag.
2) People never, ever, ever have PERFECT rhythm. Maybe close, but close doesn't cut it in a timing game.
3) If you mess up once you have to do everything all over again.
4) There's absolutely no way to edit a song once you've made notes, or continue from a point, or otherwise do anything aside from "note" the entire song start to finish.
So adding new songs is pretty much bad. But how about playing songs? Well, we've all seen the DDR ripoff format, the second format is apparently from Elite Beat Agents, and I haven't seen the third one. The DDR one doesn't work because of the poor song adding mechanic I alluded to above. I played some songs that were alright, but every last one had issues that prevented it from being enjoyable (including timing and choppiness of the game). The Elite Beat Agents one just does not work, at all. It's 100% impossible on a laptop and very difficult on a desktop. Until a touchscreen laptop comes out, that's not going to work.
Suggestions?
First, simply copy DDR's format of making your own steps for a song. You select the BPM and just put notes on a grid. Since songs are just a pattern with sounds, the ability to precisely place (and copy/paste or edit) the notes is just a given.
Get rid of the Elite Beat Agents thing and replace it with something else.
Fix the time-honored "the game jumps every five seconds" tradition of Flash rhythm games.
Add an ability to set the quality above Atrocious.
Add saving a song's custom notes locally (into a cookie or something) so you can spend as much time as you want on them.
And no, it's not my computer. At all.