I'm able to read upside down as fluently as right side up. Is this normal?

Recently i was sharing a textbook in class and was reading out loud upside down. People freaked out about it, thinking that it was creepy and strange. I can also read backwards, backwards upside down, and normally. All of these have approximately the same fluency. I know that this is probably not normal, but is there any research on this? Is my brain wired differently? I am musically and mathematically gifted.