SIO2 iPhone Game Engine is a great game engine for your iPhone or iPod Touch.You can use SIO2 for free or for commercial product. The SIO2_SDK comes with a set of 20 tutorials, and video tutorials, documentation, online support through forum, email and IM, and also include outsourcing services.SIO2 iPhone Game Engine is by far the best overall solution for 3D Game Development for iPhone and iPod Touch available out there!The free version have been used in over 30 game titles on the app store, and the indie version have been used in more than 50 titles including well known Top 10 App.SIO2 is a proven, stable, complete, easy to use where everything is working out of the box and allow you to create state of the art iPhone and iPod Touch game in a breeze.Here are some key features of "SIO2 iPhone Game Engine":