id Tech 1 is a game engine developed by id Software in the early 1990s. It was first used in the iconic first-person shooter Doom, released in 1993. This engine introduced innovative features like 2.5D graphics, allowing for immersive gameplay in a three-dimensional environment while maintaining a simpler 2D structure. The engine's success led to its use in several other popular games, including Doom II and Heretic. Its design laid the groundwork for future game engines, influencing the development of the first-person shooter genre and establishing id Software as a leader in video game technology.