Thank you very much for the answer. Now I understand. I had a look at PyGame and pyglet, but they don't seem to be available for iOS. However, if one really wanted to port the scene library to other platforms, I think they could be good starting points. So as it seems, the only thing that currently really runs on Windows, Linux, Mac OS, iOS and Android is a combination of HTML5 Canvas with JavaScript, like the demos of the cocos2d library. It would be cool if something as portable as that was also available for Python.