I have a couple of issues with phones.
1. I usually work with windows phones, which have a lower end and a high end. Usually the high end never gives me any issue, but the lower end (512 MB graphics) collapse and crashes frequently. One way to fix this was to minimize graphics or drop the quality of those. The problem is that I'm affecting everyone. I know there is a new tutorial released for Screen Mobile sizes, so I was thinking about integrating the option to select your screen. Of course, it may make the game more heavy to download.
2. Another issue is whenever we create too many particle systems, spawn enemies, etc. A friend that works in Unity uses a pool manager and that allows him to turn on/off the particles without having to create them. (I guess visible/invisible option?). I'm not sure how it really works. Do we have something similar in C2? Are the instances the same? I'm just trying to keep learning and I'm sure that someone out there already thought about this. I also would love to optimize the code to drop the crashes to 0 (which I doubt that is 100% achievable, but... I will try!)