Doom (1993 video game)
The ability for others to create custom levels and otherwise modify the game using WAD files turned out to be a popular aspect of "Doom". Gaining the first large mod-making community, "Doom" affected the culture surrounding first-person shooters, and also the industry. Several future professional game designers started their careers making "Doom" WADs as a hobby, among them Tim Willits, who later became the lead designer at id Software.
Doom (2016 video game)
In all of its platforms except the Nintendo Switch, "Doom" includes a built-in level creation tool called "SnapMap" which allows players to create and edit maps with their own structure and game logic. With SnapMap, players can create maps for different modes, ranging from single-player levels to co-operative or competitive multiplayer maps. When players are building a level, the game will shift to a top-down view. Players can place rooms and hallways to form a level and connect them together. If they are not connected together, the color of the construction pieces changes to notify the player. Players can also use the X-ray camera which temporarily removes all the walls to allow players to view the objects inside. Players can also place enemies into their maps, with the exception of the campaign's bosses. Their artificial intelligence and stats, and the player's own movement speed can also be modified. Players can also add additional particle effects, lighting effects, and other gameplay items, such as health packs and ammo pick-ups. Only in-game assets can be used, and players cannot create or import their own models into the game. Levels can be tested before they are published online.