What's so special over SE IV Deluxe?

The only major addition between SE IV Gold and Deluxe was that Deluxe added support for playing .MP3 files. (Gold could only play CD tracks.)

Otherwise, there were some cosmetic changes to reflect the change in publisher, and a few bug fixes.

The most important thing about Deluxe is that it's still in print. It gives people who only recently discovered the Space Empires franchise access to the huge mod community that grew up around SE IV.

Thou the mods & shipsets,races & ETC still come handy.

Deluxe added yet more tools for the modders, and brought CBMod's anti-missile missiles to life. CBMod and any others that have anti-missile missiles can only be processed (and replays viewed) under Deluxe, though for PBW purposes you could play it using 1.91 (but viewing a combat replay would crash you).

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Shrap - the original SE community

Note: Viewing the replay has no problems in 1.91.

Only the host needs deluxe to create the replay file without crashing.

As I understand it, the older version tries to do the following while generating the replay:
- Missile A (ID #X) hits Missile B (ID #Y) for N points of damage
- Delete Missile A (ID #X) since it hit its target
- Missile B is at zero hitpoints, and explodes
- Delete Missile B (ID #Y)
- Delete all missiles which were targetting Missile B, including Missile A (ID # ???)
At which point an error occurs since missile A does not exist.

If the replay was generated successfully, there is no problem with 1.91 reading it.
If the replay was not generated, there is no problem for 1.91 either... just no replay