Fortunately, we've created this book to teach this new language to both aspiring ActionScript developers, and experienced ActionScript developers who want to upgrade their knowledge to the new version. It doesn't aim to be an exhaustive reference, focusing on essential real world techniques to enable them to get up and running quicker. In addition, we cover how to use ActionScript 3.0 through both Flash CS3 and Flex 2/3 (open source ActionScript developers should also be able to make use of the book.)