I haven't done anything with mobile. But I'm looking at taking a viewer for a 3D world and running it on mobile. (Probably via a cloud gaming server, but that's a side issue.) So, what should the user interface be like?
On desktop, it's arrow keys or WASD to move, plus you can zoom in with the mouse wheel. If you zoom in far enough, a targeting cursor appears and you can move that with the mouse. Straightforward.
What are the accepted conventions for doing that sort of thing on a phone? Moving around and looking around must be fluid and intuitive. For other stuff, there's menus.
The Call of Duty crowd seems to like to use game controllers on mobile, but this isn't a shooter, and I'd rather not go that far.