Lovely Little Terraformations is a Doom 2 Mod. It's gimmick is that the terrain in each level changes as you play. The mod is in UDMF. It will need the original doom 2 wad.
Here is the newest version of LLT*. Not much has been changed. Most of what has been done is changing some of the textures in an attempt to give more diversity to the level-texturing.