My platform to export "should" be ios/android and as a third option PC.
The background image kills performance on low gamma graphic cards only. As far as i could test. In my pc with very high specs everything runs at 60 fps. But i see a noticeable slowdown on average pcs (like those on my office).
I still didn't make much experimentation around this problem, that's why i ask out of topic. Maybe there's a known way to win some fps when big background images are used (specially on smartphones).
Now for the real topic:
Your approach seems good to avoid using another sprite. I will check it since i'm using exactly your method for other unrelated feature.
(Somehow i miss your idea for this)
Since you used this method, would it hit performance more or less than using the second mask sprite to register inputs?
If you believe it won't impact performance then i will use it for sure.
Thanks you very much! :)