Developer of OpenGW, a game world simulation engines / entity component system with Model-View-Controller architecture that can be used with any rendering engine.
Developer of Kobold Kit, the Sprite Kit game engine with tilemap support, game components, scheduling and event dispatching, and all the other things missing from Sprite Kit.
Developer of KoboldTouch (commercial) and Kobold2D (free), both game engines build on cocos2d-iphone. KoboldTouch adds MVC and component support and even improves cocos2d's own features, such as Tilemap rendering.
Author of the Learn Cocos2D book series published by Apress. The latest edition "Learn cocos2d 2" uses cocos2d 2.0 with ARC enabled and also covers Kobold2D.
Steffen's main website is Learn Cocos2D.