Noodle Mod
What is Noodle?
Noodle is a minimalist Minecraft modification that makes small changes to the vanilla game code. The main function of the mod is adding a new world type where practically nothing generates except inverse caves. These are like tubes made of stone or netherrack, inside which you can find various ores and minerals.
World Generation Features
To create a world with the Noodle type, follow these steps:
When creating a new world, click here:

Then cycle through the available world types until you find the option called "Noodle"

Technical Details
The mod also works in the Nether. Development took less than 2 hours, so some errors and bugs may be present.