Dissatisfied with other attempts at transmuting arguably the shooter genre's most classic title, developer Chain Studios took it upon itself to create its own tribute to id Software's Wolfenstein 3D. Over the course of four months Chain built, from scratch, the entire first episode of the game using its own "Volatile3D II" engine. Now, you can play it.
The game, which is completely standalone, served as a "baptism of fire" for the studio's engine. It's not meant to represent the technology's full capabilities, but simply the fact it can be used to quickly make decent-looking 3D games.
Bloody excellent idea as far as I'm concerned.
It's rough around the edges and Chain didn't have all the resources to do it on its own. For one, the weapon models are taken from Day of Defeat, though Chain does give the Half-Life mod appropriate credit. It expands further on the game's Mod DB page:
Architecture was left intact to keep the original atmosphere, so was the original soundtrack. Gameplay contains stealth elements like the original game did: troopers patrol corridors, react sounds player produces and can take no notice of player cloaking in shadows. There are four weapon types: knife, luger, MP40 and MG42. Amongst new features there are weapon reloading (NPCs also do that) and secondary attack (iron sight for firearms).
Concept of "lives" was abolished, but player can save game at any point and there are autosave triggers on every level. Searching for secrets, collecting treasure, fighting enemy troops, cloaking and bunny hopping -- that's Wolfram.
I don't know if "Nostalgia Monday" is a thing, but today... it can be. At 195MB, it's not a huge dent in the broadband quota stakes. Look at it this way -- you'll be able to play the original Wolf 3D with iron sights. Iron sights!