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 January 9th, 2020. It was created to show 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, boss, and a reworked Icon of Sin. Although not officially devolved or published by id Software, it is official supported by them. It was released as an official add-on for the 2019 remasters of The Ultimate DooM and DooM II/The Master Levels on December 17th, 2020.