minetest/minetest — pull request #1 by Jeija (2012-10-24 17:08:31+00:00)
Title: Improved water physics / Improved state of matter system

The viscosity of liquids are defined using
groups = {liquid = visc}
visc is a value between 0 and infinite.
0: like gas
7: water
30: lava
... gets more and more viscous
It is not backwards compatible with the old system, but I guess there are just few mods that registered new liquids.

You can now also define that a node is solid using
groups = {solid = 1}
but you can still use the old
walkable = true
--> backwards compatible

The physics of water (and other liquids depending on their viscosity) have been improved, e.g. you don't just suddenly slow down.