Back in the early 90s it kind of sucked to be a PC gamer. I mean sure you could in theory get a game to run in DOS if you played around with memory settings and sacrificed a live goat over your tower, but then if you wanted to run a different game you'd have to do the same thing all over again and eventually you'll run out of goats.
Windows 3.1 was around but really it wasn't a very good OS conducive to gaming for various reasons that I can't really recall at this juncture. So your options there were also very limited. Limited to Solitare or Minesweeper for the most part. Unless you were on that newfangled "Internet" and had the knowledge on where to look. Then you might have found "Operation: Inner Space", possibly one of the most groundbreaking games ever to exist in the history of PC Gaming, and probably not that well known. That game was Operation: Inner Space, created by Software Dynamics, who are better known for giving the world the Flying Toaster.
The concept of the game is as such. The Evil Kilokahn lives inside of computer circuits. With the help of Malcolm Frink, he designs Megaviruses to...wait I'm thinking of something else aren't I.
Ok starting again. The Inner Demon lives in your computer. He has sent out viruses to corrupt your computer and its files. You launch in a ship that enters your computer via the screen, in an attempt to secure your files, and eventually defeat the Inner Demon. What sounds like a very simple premise actually belies the much deeper game at hand.
First off, the files you're attemtping to liberate are your own files from whichever drive you select at the start of the game. These files fortunately are not in any real danger (unlike that one game that tried to present itself as a morality play, fuck that noise), but it does mean you'll see the actual icons for your files as you play and head through directories.
Also, you are not the only ship navigating "Inner Space". Ships from various factions will also appear. Some will be friendly, others will be neutral to you (most likely the cops but more on them later) and some will be downright hostile and attack you at the slightest provocation. Unless of course they're pirates, in which case they just want your precious, precious resources.
See whenever you pick up an icon, you get a resource value attached to it. Usually an icon counts for 1.0 resources, but depending on its condition (since things like weapons fire and rocks can damage the icon) you might get less than that. Resources are basically your currency in the game, which you can spend in the Ambulance (a roving ship you can summon that looks like the Software Dynamics logo).
Anyway back to the ships and the factions. Every ship is unique for the most part, be it in its paint job, its characteristics, or its secondary weapons. Weapons that range from the typical (heat-seeking missiles, flamethrowers) to the ridiculous (flying batteries that electrocute enemies, a defense system that turns incoming missiles into harmless food items).
Ships also tend to reflect what faction their from. The "Fuzzy Ones" faction for example flies ships that are all based around animal motifs. The "Speed Demons" fly ships that evoke a fast look (ranging from fighter jets to sports cars) and so on.
Keeping all of these factions in line, or attempting to at least, are the "Enforcers", the police of Inner Space. In some levels (known as "waves") you may encounter one of their patrolmen, who basically just keep an eye out for any scofflaws who do things like destroy healthy icons on purpose, steal resource packs off of dead ships, or...shoot the police officers. If any thing of that nature should happen an Interception craft will be called in to handcuff (literally) the offending ship and take them to the Hall of Justice (if I'm remembering the name correctly) to mete out punishment. If the criminal in question evades the Interceptors and continues to break laws, a Terminator might get called in. These are essentially craft designed to kill offenders who have become too dangerous. This can happen over a period of many waves.
That's what's really intriguing about this game. While not a true persistent world in a sense it does have the basics of one. Allies will remember you helping them from previous waves. Enemies will remember you fighting with them or killing one of their buddies, and the Enforcers will remember the kind of shit you pulled many waves ago. In addition, how much a faction likes you will change depending on how you interact with them.
As well as having a decent memory, the AI is pretty decent for its time as well. Allies will radio you for help, come to your aid when asked, and generally will not do stupid things like shoot you in the back or suddenly develop interest in a shiny object while you're getting blasted to pieces. About the only time AI buddies will not come to your aid is if they're in bad shape themselves, or out of fuel.
There's also other nice little touches made by the developers of this game, such as integrating the time of day with the game. The intro will say "good morning", "good afternoon", "it's late" or some other phrase depending on the time of day, and if you should be playing in the morning you may be surprised to find the fuel cans in the game replaced by floating cups of coffee (with the same effect of course).
But enough about that, what about that plot I mentioned before? Well suffice it to say the plot isn't exactly central to the game experience, and that's ok. Waves feel varied enough in layout to not get too repetitive, and there are some nice diversions (dueling, races) to break up the monotony. However if you want to end the game without collecting every file sitting on your hard drive, you'll eventually have to face the Inner Demon.
From time to time the demon will open up a rift in Inner Space, essentially a black hole that will suck you in. The object here will be not to fight the Inner Demon, rather instead to "feed" the 4 dragons guarding him at the edge of the arena. Feeding them (by shooting them, natch) will release the "noble weapons", 4 weapons that you cannot get anywhere else, and they aren't so much weapons as they are impressive defensive measures (ability to deflect weapons fire, for example). The idea being that once you have all 4 noble weapons, you can then finally confront the Inner Demon and defeat him once and for all on your own terms. But I've never done that. Usually pirates end up fragging my ship before I can reach that point. Yes I admit, I've never beaten this game. Partially because I only played the shareware version, but also because the waves do get progressively more difficult, especially if you rack up a lot of kills of enemy ships.
Aside from the game there's also a ship editor that you can get for it which is simple and intuitive to use, and adds more longevity to the game. While I'm not sure the game is worth the $25 they're still charging for it (yes, you can still get the game from Software Dynamics), and I'm not sure it'll run on a 64-bit OS (though it did run on my 32-bit copy of Vista Ultimate), I'd say it's at least worth a look at the 14-day trial, if not an actual purchase. Inner Space is one of the most overlooked gems of 90s PC gaming, and I can honestly say it's one of the few "unique" games still around.