It's a nice game overall. But it could have some improvements to make it better. Such as:
-the beat spot could be at the center insted of the full left so we could see the enemies better and decide which way to shoot, otherwise we spent the whole gameplay only looking to the corner.
-The devil introduction could have a skip button and some kind of sound, for a moment i though my audio had bugged.
-And last but not least, i think the music is nice and lively but a lil bit to repetitive so as a rhythm it's not the ideal, if it started more slow and had it's high pitch it would be more exiting.
For a only 48 hour game and since you had to spent most of the time making the music combine with the keys i think you did a pretty good job. But well, i hope my sugestions can be good for a next time try ^^. Nice game and nice video!