- used scaleX (-1) to flip the instance of the (left) button.

- used a mouse event (advanceClick) set up as an if/then statement to advance to the next set (based on maincount).
If it's less than 15, it advances by 4 (else it goes back to zero).
For the left button... if it's at 0, then it goes back to 16 (else it subtracts by 4). that's about it... nothing too special.