Extermination Day is a ZDoom map pack that uses many zdoom features, and allows the player to freely make use of jumping, crouching and even rocket jumping without worrying about breaking the game flow. The maps are specially aimed at Zandronum's online cooperative play. All maps will have 8 player start locations so a lot of people can join without causing telefrags at the start, and all maps will have almost twice as much monsters in multiplayer. Some maps will also feature Deathmatch and maybe Invasion versions. This wad will also feature a hidden ending, that can only be achieved by finishing the game on the Ultra-Violence skill or higher.