Crossover has limitations, restricting where you can go. West of the Variable Sea is a strange, stretchy barrier that keeps you from traveling far in that direction. Everything north of the Crossover valley is cut off by something called the Black Billow, a dark, thick substance no one can make their way through. To the east and circling around to the south is a high, extensive ridge known as the Rim. No one has managed to reach the top to see what lies on the other side. Those who try are stopped at a point where everything—rocks, turf, and the ground underneath—start to grow insubstantial.

That’s not quite all. There’s the Jelly Wall too, a short section between the western end of the Rim and the Variable Sea. The Jelly Wall is the last barrier stopping exploration. It has this advantage, however: you can run towards it, fling yourself against it and get harmlessly thrown back. Great fun, unless it rains. When it rains, the Jelly Wall goes slick.

“Baby gates,” David Mahaffey calls these barriers, “like someone or something feels we can’t be trusted and wants to keeps us restrained.”