Hi, i'm just wondering if it's easy to make you're game Multiplatform later in development, say you are about to release you're game on the IPAD and you decided you want IPhone users to be able to play aswell, would you have to change things such as a programming language or are C#, Boo Java compatible on any platform?
Thanks For Reading
Whether your game will work on multiple platforms is more about the features you use and your content than about the language. C# and Javascript will work on all platforms (though some platforms may be on different .NET version). Boo is not supported on Android and iOS. Have a look at the license comparison page for more information.
Also consider your content -- lower-end platforms will require lower-poly models and smaller textures.
Input will also need to change, for example to replace keyboard and mouse input with touch input.
It's best to consider all your platforms up front, and even if you don't implement for all of them at once, at least keep the capabilities and limitations in mind as you design your game.
It is best to decide these things during the design phase because what you would normally want to do is create your game engine with an entry point. This entry point is how you talk to it.
You can then create a "wrapper" for any OS or platform you want because the engine will speak the same language no matter what. The wrapper translates that information between the OS and the engine. (ie. input, creating windows, setting up the display environment) The engine doesn't really need to know about these things it just needs to be able to tell the front end what is going on.