Funnily, his site has an issue that he could avoid, or would have noticed if he used Macs! If you're on a Mac, it might be why you're not fully happy with the effect. The problem is that Macs don't get Flash events when the right button is pressed, or when you're dragging on some of the browser window chrome. As you resize the window you'll see some jerky motion, because when the resize event itself happens Flash gets a chance to try to catch up. Trying his site on Windows, even in an emulator on the same Mac that doesn't do so well, gives the fluid motion you wanted. You can get the same effect on a Mac by resizing the window and quickly releasing the mouse and pointing into the window again. If you're quick enough you get some of the tweening effect. So, don't do things that way! Instead instantly move your elements to the right place when the resize event happens. Your user becomes your tween engine, and having everything instantly lay out according to to the user's window resizing movements is gratifying enough. Incidentally, there's already a request into the Flash team to solve the problem about right-clicking stopping Flash events, I'll add a note to that request to point out that browser window resizing shouldn't stop the Flash movie too.
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