At any point in time, the map would look something like the following, where the player's position is a the centre of the cross (the 2 surfaces).
Code: Select all
3
1265
4
Code: Select all
5
136
2
4
I imagine that it would play something like Seablock, where if you create enough landfill, you eventually end up making the planet bigger.
An infinite-reseach that consumes an ever-increasing amount of landfill and each tier increases the size of the cube by 2 tiles on each side (so that everything remains rail-grid aligned).
It might be simpler to support expanding the planet if special underground pipes / belts are used to join the edges; when the edges are aligned they should just work, if they're not, stuff needs to be moved by script; when the planet is expanded, they should keep working if they're close enough to the edge.