Technostein SSD is a mod for registered Wolfenstein, made by AstroCreep. It was released on May 22, 1999.
It features a handful of new graphics, supposedly giving off a futuristic vibe. No new levels are featured.
A storyline is nonetheless attached, and is as follows:
It is 2055, and you are B.J. Blazcowicz's great-grandson. You are thrust into World War III, and the Nazis have stolen microchips and toxic objects for an attack on the U.S. Since you have the same strength as your great-grandpa, you were assigned to go in the dreaded Castle Wolfenstein to face the Nazi forces. What's worse, there are rebuilt versions of the enemies your great-grandpa faced. Dr. Schabbs' grandson has recovered plans for Operation: Eisenfaust. He has rebuilt Hitler and Hans Grosse. Cyber-Hitler is in a bunker underneath Castle Wolfenstein, Schabbs is in a secret lab in the castle, and Hans is all over the place. Now, load your Allied Handgun, and go to the castle!