Make Factorio 3D. Adds special belts and power poles that allow sending items and power "up" and "down" freeing you from the limits of a 2D world.
Augmented or new ways of transporting materials - belts, inserters, pipes!
Play it your way.
How can I travel to a different level myself?
There are keybinds for traveling up and down (defaults to Control + Up/Down, I've found Control+Shift+Mouse wheel is nice).
Honestly though, this mod is still very WIP, has a number of known crashes, and will probably be changed a lot shortly. Make backups.
Perfect, thanks! :)