Admiral Gobi was made without using the expensive Flash CS, but instead written directly in ActionScript 3. Most hobbie/independent developers who create Flash games outside of the designer-oriented Flash IDE seem to do so in the free and open source FlashDevelop, which is Windows-only. Since I run Linux, I instead used the lightweight Geany editor to do my coding.
My first small Flash demo games were written without the benefits of a framework like FlashPunk, which Admiral Gobi uses. While FlashPunk makes some things easier, I think working with a framework before really developing an understanding of Flash and ActionScript 3 basics will lead to more trouble later on. I've already had some difficulty integrating a few of Mochimedia's services into the game, because FlashPunk is intended to be used with it's own classes instead of the standard Flash Sprite and MovieClip objects.
I have a copy of Essential ActionScript 3.0 by Colin Moock, which seems to be everyone's recommended ActionScript book for people who already know how to code, but I've only skimmed it so far. Reading the whole thing is going to be an endeavor, but hopefully a worthwhile one. I intend to write my next game without a framework and see how it goes.