Thanks again!

At first the portals showed a simple preview of the level using render-to-texture but somehow this did not work out and it looked pretty bad. Now I will just put a level preview in the background as stated above (I used to have preview images before the hub world but I found that to be too old school/ antiquated).
You cannot really "select" a level in the hub world, instead you move around freely and when you want to enter a certain stage jump into the corresponding portal (and hold Up + Action key).
I've tried my text3D approach which I posted some weeks ago first but the text was either too huge or too unreadable (because of no/ FXAA, in both cases bad), especially on screen resolutions below full HD (EDIT: The stage and coin numbers are still text3D, though). As a result I had to draw it onto the screen instead. The level info box visible in the screen shot fades in smoothly when you approach a portal but I don't like the placement of it yet. Maybe I will try to implement a vertical information bar at the left/ right side of the screen (which could look disconnected and/ or inconsistent, though).

The ultimate goal of course is to get the game on Steam first, then add other options such as Desura and the like later, one at a time. This is obviously no easy task, especially the former, but I have some sort of plan I build my hope on to get enough publicity.