The Doomsday Engine is a portable version of the classic first person
shooters DOOM, Heretic, and Hexen. It lets you enjoy the original games
using modern technology, including high-resolution OpenGL graphics, 3D
models, and dynamic lighting effects.

Data files from the original games are not included; you must acquire
a copy of the original games from id Software and/or Raven Software.
You may also use free alternatives such as https://freedoom.github.io/.