Sq2 is a world dominated by ruined cities. The terrain is based on two-dimensional perlin noise for speed and simplicity. It's very similar to Squaresville_c, but all done in lua. It's based on singlenode, so no matter what mapgen you pick, you get Sq2. For those who've seen my earlier mods, this mod incorporates most of Geomoria, Fun Caves, Zigg, Exeter, Passages, Chaos, Loud Walking, and Big Trees.
At the moment, it produces some nice wilderness with rivers, roads, and an occasional ragged grid of streets with ruins scattered about. There are passages, dungeons, and pyramids to explore. The cave system is unusual -- it generates large, horizontally open spaces with small and large speleothems and a variety of biomes. I plan on supplementing this with cave geomorphs in the future.
There is a chaos dimension, accessible with the Trump of Chaos, full of familiar terrain twisted into bizarre shapes, including little "planets" with soil and vegetation and "stars".
Using the geomoria-based geomorph system, you can add any sort of ruin or dungeon you can imagine with simple lua code. You can also modify or create new cave biomes as easily as surface biomes. (See the init file for the biome table.)
Note: Because of the way minetest handles multiple processors, you should set "num_emerge_threads = 1" in your minetest.conf file when using Sq2 (or any lua mapgen). This will significantly increase the terrain generation speed, and avoid any issues with overgeneration.
This is a work in progress.
Spoiler
Code: LGPL2, textures: CC-BY-SA and CC0
Mod dependencies: default, beds, doors, flowers, stairs
Download: https://github.com/duane-r/sq2/archive/master.zip