Update
This mod is currently in "maintenance mode" as I am working on a complete rewrite. This means I will not add any major features to this mod, but any feature you suggest will be considered for the new mod. Also not that I'm usually quite busy with university, so it may take a while for me to fix issues or make progress on the new mod.
More information about the new mods can be found here:
About this mod
This is a port of the Surfaces mod by Simcra for 0.17, based on Surfaces_remake by Erdbeerbaer. Initial efforts for porting were made by DeltaNedas and further changes were made by Danacus.
The Surfaces mod offers you the opportunity to exploit the natural resources of the planet through the ability to dig caverns of limitless depth (granted this may seem a little crazy, the time required to find resource nodes gets exponentially larger, especially when using RSO or other resource altering mods). In addition to adding underground resource-rich surfaces, this mod also allows players to create surfaces above the main surface ("nauvis") and will require them to build tiles before they can start utilizing sky surfaces. This mod provides the means to successfully transport liquids, items, electricity, players and circuit signals between these surfaces without requiring constant player interaction.
Source code: https://gitlab.com/Danacus/surfaces-redux