Hi guys,
Im new around here and very much interested in Unity. Im very interested in “multi platform” side of unity. Is it actually possible to have a game and then port it to web, desktop and mobile platforms? If possible, how difficult would that be to do that ? Is there any potential problem I need to aware when portting a game to various platform ?
Just the different model details, and if your using touch screen or not 
at least I think thats it …
Its very possible especially if you are as reasonable as you seem as you mention “port it to” (not as others expect 1 click works everywhere).
But as spmedia mentiones, you will need to have assets opted for the platform and correspondingly optimized and focused input methods. but other than that, its only a matter of doing it and buying the licenses and addon licenses depending on platform 