How do you develop games for multi-platforms in 1 single project

don't forget about using #if in the preprocessor

http://docs.unity3d.com/Documentation/$$anonymous$$anual/PlatformDependentCompilation.html

regarding UI many people use one of the various "gui" packages because it's just such a nuisance doing different sizes

if you use 2DToolkit, it now automatically makes sprite sheets for different platform sizes

unfortunately there is no solution (fundamentally) other than just to program it, ultimately using "screen.width" and so on. again in general many people use one package or another to do UI and similar problems, for just this reason

eg http://answers.unity3d.com/questions/384623/setting-font-size-according-to-screen-dpi.html

Thanks Fattie. But I wonder how to distinguish iPhone4 iPhone5 iPad IPAD $$anonymous$$INI in Unity3d, since they all belongs to RuntimePlatform.IPhonePlayer.