Typically, all later versions of flash players (11 and above) are only able to display 30FPS (33.333 millisecond) or 60FPS (16.667 millisecond) frames. For SM63, this means most frames are 30FPS, with a few 60FPS frames thrown in. The new, modified versions allow any frame lengths, which means all frames are pretty close to the mean value of 31.125 milliseconds, giving a smoother experience. Either version can be used and is allowed on the leaderboards.