compatibility of mobile apps: add code or something else?

I’ve noticed that alot of the samples don’t seem to support mobile devices, such as the truck car game or the platformer game. First, is there a way of knowing whether or not it is mobile compatible before downloading
? And also I was wondering, does the user have to add their own code to make it mobile compatible, or is there something I am missing or a simpler way to do it? Thanks.