We assume you know some object oriented programming and we do teach you all the Objective-C you need to know to make an iPhone game with Cocos2D. Our last tutorial/project involves making a one-level Angry Birds clone. All of our games (https://app.makegameswith.us/) so far were built by students who learned through our tutorials. Nobody had touched a line of Objective-C before we got to them as far as I know.