Note: This game was played on a source port called ECWolf and I wholeheartedly recommend downloading it to better your experience with the game, adding a few modern features, more resolutions, and turning off the Y-axis so moving the mouse forward doesn't make you move forward as well.
I'm going to go out on a limb here and assume most people have heard of Wolfenstein 3D already, but just in case someone hasn't here is a brief history.
Though not being the absolute first of its kind, Wolfenstein 3D is a game highly regarded as the progenitor of the first-person shooter genre, created by id Software in 1992, no mater what anyone may say about how good the game is or not these days, it at least has to be respected for the creation of one of the most prolific video game genres to date.
You play as William Joseph "B.J." Blazkowicz, a Polish American spy sent on a mission to find out the nazi's plans and stop them, which usually means climbing nine floors and murdering someone at the top or bottom, along the way killing S.S. troops and undead mutants.
As you can tell, the story is not really all that important, as famed programmer for id John Carmack once said, and I quote, "Story in a game is like a story in a porn movie. It's expected to be there, but it's not that important." So given this mentality you can pretty much write off the story as just a means to let you shoot stuff, and this was back before most games even bothered to put effort in their plotlines to start with.
So that means onto the gameplay, ever played a first-person shooter before? Well then you will fit right at home, the game is simple as far as controls and objectives, you walk around and only are able to look left and right, fighting in stages of block shaped rooms and mazes, looking for keys and doors to get you to the final switch, pulling it and moving onto the next level, there are six episodes and each one has nine levels and one hidden map that is gotten to by finding a hidden elevator in one of the stage, totaling sixty levels in all there is actually a lot of game here.
You have three gun types and a knife, though the guns all use the same ammo counter and about the same damage except each one shoots faster then the one before it, levels are sometimes straightforward, and sometimes mazes you must run through, most of the level design is fun and varied up to a point, given they don't have very much to work with other then walls, floors, and sometimes hanging moss.
The big question is if it is worth playing, and actually even today, over twenty years after its creation, it is still fun to play, sure it is simple and chances are not anything you haven't seen before from more modern shooters, but it has that old retro charm to it that is hard to explain, it is bright and colorful, has treasure and arcade-like qualities such as lives and a score, and despite how old and dated it seems, I still believe it is worth taking a look at.