> 
Zebbi did you ever hear back on this other than in this forum?
>
Unfortunately, no, it looks like it's going ignored, I'm afraid! Maybe we can ask 
Ashley nicely again.
Being able to ignore specific solid/solid types seems like a no-brainer, especially in terms of optimizing collisions. Unity has layer-based collision (https://docs.unity3d.com/Manual/LayerBasedCollision.html), and it's not hard to imagine why similar functionality, or some kind of tag system for collisions (also in most other engines), would be useful in a 2D game as well. Every little bit of optimization can help, across all platforms. Hopefully Ashley and co look into this. Even extending it to other objects types, like bullets, would be great - bullets may not need to track if they're colliding/overlapping with each other at any point, for example, so that check could be ignored - though I suppose any benefits arising from that scenario would depend on how C2 is checking for collision/overlap in those circumstances to begin with. Heck, just being able to manually set collision cell size (this matters a lot when the "camera" zooms in/out) instead of having it set automatically to theoretically avoid misuse by less experienced users would be a big step...I've never understood the "we don't include this feature because some people may be confused by it" mindset that exists around C2 development.