Replying to Guitar Hero induced Hallucinations

Yesterday, I played Guitar Hero 2 for the first time in my life...needless to say, I sucked, but something odd happened after watching my other friends play for a good half hour. It must have something to do with the constantley moving screen, because I noticed after watching for long periods of time and then looking at something stationary that it would grow and shrink. If you have ever done that thing where you look at the spiraln top for thirty seconds and then look at your hand and it appears to shrink or grow...it was just like this. I wasn't on anything and it kept happening as long as I watched the game for a while. It kinda freaked me out at first until I realized it was just the game messing up my vision. Anyone else experience this? I can only imaging what would happen if your were on something...imagine playing guitar hero while shrooming.