1 on 1 Orbital
This map seems rather sparser than the previous two in Icedude's "1 on 1" series, 1 on 1 Amateur
and 1 on 1 Sequoia - to me that made it seem rushed, though Icedude assures me that he just wanted to have a less cluttered effect.
That darker circle near the cursor's cross-hairs is a teleporter, which moves you up to that rather nice-looking blue-and-nothing walkway. Each end leads you to a window into space. Step through one and be prepared to go "Whoaa!" as you drift off to your doom - much the same can happen with the other one if you are not careful, but a simple jump gets you across to a small and very simple "space shuttle" provided by the Rockheads, which acts as this level's "hidden room", with the usual sort of pick-ups.
So, I suppose this ought to play pretty well, taken in the right attitude. Still, I prefer the other two in the series... The textures, if minimal, are suitably orbital, and the "step into space" effect is nicely authentic, so you may like it better than I do!