Mods introducing new content into the game.
Original credit - AnotherZach - mods.factorio.com/mod/dark-science. Adds a darker version of the vanilla science packs, such that you need to research both the vanilla pack and dark pack to progress. This mod is a lighter - lower cost - version of the original. The rework is limited to the base game, space-age is as AnotherZach wrote
Mods introducing new content into the game.
Providing the player with new tools or adjusting the game interface, without fundamentally changing gameplay.