This book is for ActionScript developers who are trying to create Starling cross-platform games. Prior knowledge of Starling will help, but is not necessary. The flag defense game covers some complicated topics in game development which is beneficial even for those who are already creating games with Starling. JavaScript experts who do not know ActionScript but have the willingness to try can also use this book, but it will be a steep learning curve.

I personally believe that if you are an expert at any single programming language, then you should have no trouble learning another one very easily. What matters in game development is the right application of logic, the willingness to learn, and to update, not the language of choice.