the light on the background follows the beat of the music, it doesn't happen much during kiai time though, i found this after having some sort of glitch when playing Multiplayer, pretty cool in my opinion, did peppy finally put some math to the game? O_o (just kidding:P)
remember it's the light on the background, not from the sides of the screen
i have another video like this, i can upload it if someone want it.