Special notice! While MC Tween is a nice extension and it will continue to work for AS1 and AS2 until the end of time, it is my duty to inform all citizens that I have switched the focus from further development on MC Tween to a new AS2 and AS3 extension, a real Class this time, called "caurina.transitions.Tweener" (or just Tweener). Tweener doesn't have as many features as MC Tween yet (for example, it doesn't have native filter tweens), and the documentation isn't 100% done, but it features a complete, more solid redesign with a few additional syntax features that were impossible to achieve with MC Tween. And it works the same for AS2 (including Flash Lite 2+) and AS3.
So, if you use MC Tween, or you're thinking about using it, I'd like to suggest you try Tweener instead. It follows all the principles of simplicity I tried to feature on MC Tween, but with a more powerful syntax. Tweener download, examples and documentation are available on Tweener's page. You can read more about this change on this blog post.
Thank you for your attention and sorry for this ugly box. And don't worry, this website will not be deleted or anything.
Notice for October 2008: also note that, if you are still interested in MC Tween and don't want to use class-based AS2 or AS3 solutions, Larry Benedict has taken the matter into his hands and updated MC Tween with some filter features that are not available in the latest version. You can read more about it (and download his version) here or here.
All you need to install and run MC Tween is its MXP file. This MXP file is understood by Macromedia Extension Manager - it's already installed with your normal Macromedia product installations. If you download it and it doesn't run, be sure to download the extension manager from here. This extension is 100% compatible with Flash MX, Flash MX 2004, Flash 8, and Flash CS3; from the Extension Manager, you can select which version of Flash to install to (if you have two or more versions of Flash installed).
If you are installing to Flash CS3, however, you will need the new Adobe Extension Manager, available here.
After installing, the include file (mc_tween2.as) as well as the XML syntax/help file (mc_tween.xml) will automatically be added to your Flash installation. You can then use #include "mc_tween2.as" to use it, as instructed on this section of the site.
To learn what's new on each version, please read the source .as file itself. The complete changelog is at the beginning of the code.
A quick note about version numbers: the first number is the major version of this extension - it's on version 2 now, and probably there will not be a version 3 (the change to '2' was needed when I changed a lot of the internal workings of the extension). The second number is changed when a new feature (like a new method or a new shortcut) is added; and the last number is changed when there is update with no actual new features (like a performance increase or a bug fix).
There's also a separate help file download. This file installs this documentation inside of Flash itself, so you have it available when you press F1. The documentation was converted with help by Alfredo Santamaria.
Apart from the normal installation, separate files are also available. They're useful for quick pasting, or if you don't have Macromedia Extension Manager installed and don't want to install it. If you download the normal installation file (above), you don't need any of the following files!
There are also other(alternative) versions of MC Tween available. To use them, download the selected .as file, place it on the corretc include directory (or your movie's directory), and #include it on your Flash movie. They should be used in place of the standard MC Tween include file. See the files themselves for more information.