Your mockup imposes limitations, mainly having to do with canvas (or also window sizes)
This only applies to mobile, and I think you said you were developing for mobile (correct me if I'm wrong)
Your picture implies (if I'm correct) that you also want the canvas to change in size, but if you're on a mobile device, this is not a good idea, generally speaking. You can change the canvas size in System (and therefore, the window size), but with mobile devices, this is a bad idea.
It has to do with one, phone resolution (varies between model/brands) and two, while the following is a general guideline: there is a widthxheight limit defined as a 'safezone', this describes if as long as said limit is not surpassed, a game will display fine on almost any mobile device.