Following some feedback on reddit regarding the price of the source code, I've decided to offer people who'd like to get access to the source code accompanying this series of articles a few choices.
Totally free version
Click to give focus, then cursor keys control the green player character.
This versions contains the bare essentials of the game, one player character, one map, one tile type, no level progression, no enemies, no fancy graphics, or dependence on the Flash IDE. Basically, everything you see in the demo above, including the nice robust camera system.
This version is recommended for anyone who wants to get a pretty decent code framework in which to build their vision of the game or for anyone who is interested in sampling the quality of my code before making a purchase of the other, more advanced versions.
Update: this version is now available on IOS, courtesy of Gabriel Sanchez who wrote an article about the port. You can read it (and download his version) here: http://gabrieldsblog.wordpress.com/2013/12/29/2d-platform-game-ios-port-part-1/
USD 9.99 version
This version contains all the assets of the full game, but only one enemy type, no level progression, no parallax layers and no ladders.
I'd recommend this version for those who are interested primarily in having a very solid framework with a good set of features, have a strong desire to put their own mark on the game and a willingness to experiment and learn.
USD 19.99 version - SALE: reduced from $49.99!
This is the complete version, with everything included.
I'd recommend this version for anyone who wants a nearly complete game they can make their own. Just by re-doing the gfx, and adding more levels you will have a completely unique and fun game.
USD 49.99 version
This is the complete version, with graphics redone by Khan Studios.
I'd recommend this version for anyone who wants a neat tile-set and animated character set to go with the project, and to use in whatever else they see fit.