Since the player in Epoch has the ability to go for a spacewalk outside Marsi-3, it was inevitable that I needed to use an 'endless' room for simulating the infinite space he drifts in. Something like the desert of King's Quest V but with a little twist: you can mark a place you already visited in a specific part of the screen. I've used water for the space map, it vaporizes immediately and then freezes as little water crystals.
On the other hand, the deserts of Titan are marked by little marking flags that the player is supposed to find earlier in the game. Of course due to the non-linearity in Epoch, you can find a map of the worlds in alternative puzzles solves, or make another character do some of the tasks you need to perform on different locations on the maps.