I really like the music as well as the sound effects, too bad there's only two levels, the idea of a rhythm game and top down shooter works well but I sometimes panic XD, the art might need some work as it's only square and circles, but the particles are fine since I can guess where the enemies are, you could use something like post processing to compensate for the lack of art, a pause menu would also be good since I accidently click the restart button, so yeah need improvement is art, more music and a feature to create you own music.
Good job I enjoy that :D