Dive into the world of Lignumis, a moon of Nauvis offering only the most basic technologies.
Mods introducing new content into the game.
New places to build more factories.
Augmented or new ways of transporting materials - belts, inserters, pipes!
Map generation and terrain modification.
New Ores and resources as well as machines.
Things related to oil and other fluids.
Furnaces, assembling machines, production chains.
My personal (and probably really lame) take is that you should be able to unlock boilers with the mine 1 iron trigger tech (instead of aai needing green science for boiler and steam engine) once you get to nauvis to make steam assemblers useful :3
