Duke Nukem 3D had a stock level (E2L11, "Lunatic Fringe") that did something similar. The main structure of the map was a 720-degree loop. I remember it took me

Duke Nukem 3D had a stock level (E2L11, "Lunatic Fringe") that did something similar. The main structure of the map was a 720-degree loop. I remember it took me a good long while to figure out what was going on the first time I played it.