I set up my in-game UI using 2D Toolkit UI. These are 2D icons and text that are positioned using anchors relative to a tk2dCamera, all in the corners of my screen.
My intent is to use a single sprite sheet that is authored at retina pixel density. I want to layout / size my UI elements once and have the appearance of the icons and text be the same physical size across all devices and platforms. I'm only using 2DToolkit for UI in this particular project, and the UI is very simple, so I'm not interested in authoring resolution-specific variants for every piece of 2D art. I want to use a single sprite sheet for all targets.
In other words, an icon that occupies 96x96 pixels on an iPhone 4 screen (or iPad Retina screen) would be drawn in 48x48 pixel space on an iPhone 3GS, or an iPad 2, or a PC.
I'm still quite a bit confused about "native resolution" and "overrides" and so forth, so would greatly appreciate a straightforward explanation of how I can do what I'm trying to do.
Thanks!