Devolved by Iruka Software for the 25th anniversary of Doom II, Doom Zero, stylized as DOOM Zero, is a mod for Doom II released on September 30th, 2019. It was created to push the boundaries of the vanilla Doom Engine. Its gameplay is heavy with puzzles, multiple pathways, and surprise encounters. It also features a brand new enemy and a reworked Icon of Sin. Although neither developed or published by id Software, it's officially supported by them. It was released as an official add-on for the 2019 remaster of The Ultimate Doom and Doom II/The Master Levels on December 17th, 2020.