You will get to notice anyways during the compilation process, because usually compiling with the wrong tool version, will spit out tons of compilation errors. If you, for example, decompile CS4 files and recompile them CS6 (which is perfectly feasible if you're upgrading, but not downgrading), they will create bugs in game, like weird symbols and messed up UI elements. You will need to keep in mind, that if you compiled/decompiled a file with either CS6 or CS4, you will need to recompile it with the same tool. swf/.gfx I recommend, by proposal of SkyUI team and due to personal experience, using Flash CS4. To create Widgets from scratch, I recommend using Flash CS6, to modifie existing. You can download Sothink Decompiler to speed up decompilation and do basic stuff on. Tools like Trilix, SWiX or Sothink are good for basic 'code hacking', but not for serious development of Flash elements. You will need Adobe Flash tools, this is inevitable. Prepare for a long, long journey So let's begin: This tutorial will, more or less, teach you how to create a basic widget with Flash tools. But now that my wife isn't home, I think it's a good opportunity to fulfill a promise and make this tutorial by popular demant. Lately I had to keep a low profile due to various issues, probably all related to me spending to much energy into our all most famous hobby, modding.