Consider all these features that ZDoom has that are not found in the standard Doom originally released by id:
* It runs well under all modern versions of Windows, from Windows XP to the new Windows 10. If you have Mac or Linux, it works with that too.
* Can play all Doom engine games, including Ultimate Doom, Doom II, Heretic, Hexen, Strife, and more.
* Supports all the editing features of Hexen. (ACS, hubs, new map format, etc.)
* Supports most of the Boom editing features.
* Many more all-new editing features such as:
* Colored lighting.
* 3D floors.
* Advanced polyobjects free from the restrictions of their original implementation in Hexen.
* Custom monsters, weapons, items, player classes, and other entities.
* High resolution textures and sprites.
* Translucency (regular and additive).
* Many, many extensions to ACS that were not present in Hexen.
* More music formats: Ogg Vorbis, MOD, XM, IT, S3M, MIDI, and MP3 as well as old-fashioned MUS all work.
* More sound formats: FLAC and WAVE can both be used for sound effects.
* More texture formats: PNG and JPEG are both useable for artwork.
* All Doom limits are gone.
* Several softsynths for MUS and MIDI playback, including an OPL softsynth
for an authentic oldschool flavor.
* High resolutions.
* Quake-style console and key bindings.
* Free look (look up/down).
* Jumping, crouching, swimming, and flying.
* Full-featured joystick/gamepad support under Windows.
* Up to 8 player network games using UDP/IP, including team-based gameplay.
* Support for the Bloodbath announcer from the classic Monolith game Blood.
* Walk over/under monsters and other things.