OK, let's get this out of the way right now.
You will die.
You will be poisoned, diseased, irradiated, blown up, and electrocuted. You will be hungry and starved, your equipment will break, your armor will fail, and your ammunition will run dry. You will be stunned, confused, blinded, and terrorized. You will be shot by crazed security robots, shredded by mutated terrors, and gnawed on by countless foes, and occasionally disintegrated.
...so, you've got that going for you.
Overview (what is it?):
Sword of the Stars: The Pit is a turn-based top-down roguelike, where you play a character exploring a hostile and ancient alien complex trying to find the cure for a plague that is running rampant through the worlds.
Well, for those unfamiliar with roguelikes - this game is not meant to be beaten in a few hours then discarded. As my introduction stated, this is a challenging game, with permanent death (the game mechanics prevent you from saving, except to exit the game) and you can only have one active game per character class at once, so you'll frequently watch as a character you've invested hours of gameplay into is wiped out or overwhelmed. Because the game is randomly generated each time, sometimes bad luck will end a good run with not much you can do about it. Your character has several limiting factors to keep in mind - ammunition is limited, and can only be replenished by finding more (which, depending on the weapon, may not be that common). Food is a concern as well, as there is a hunger mechanism that makes starving a real possibility if you can't find or make enough food to stay alive. Disease is a concern - not just from infected creatures, but perhaps by being forced to eat things you shouldn't... And, of course, there's just running out of hit points and dying at the hands of the denizens of the complex!
Gameplay itself is turn based, with you and monsters alternating turns (though, if no monsters are visible or present, your turns run seamlessly together making it easy to move around). each turn you have a limited number of movement points to move around the grid squares and explore the complex, looking for abandoned equipment you can scavenge or repair, old lockers that might contain food or items you could use - and, of course, creatures that may still be lurking! Somewhere on each level is a hatch leading to the next level below, with monsters getting tougher as you descend.
The interface is a nice balance of being easy to get used to, though does take a quick reference of the manual to learn some of the finer points. generally, you move with the awsd keys, and use the space bar to interact with objects you face. 'Interact' is case sensitive; for a locker or a freezer, it'll be 'open', a locked vault will be 'unlock', a broken piece of equipment will be 'repair', etc. Combat is similarly simple - equip the weapon you'd like (or select from available hotkeys), and click on the target. (And, yes, there is a good tutorial available to teach you all this stuff!)
Overall, though the game itself is simple, I found (and still find!) it interesting because some of the choices the gameplay provides. I'm hungry - do I dare risk eating my tainted meat, or press a little further in hopes of finding something more suitable? The room ahead is heavily guarded - is it worth the ammunition I'll use (and wounds I'll take!) to clear it in hopes of finding equipment I can use, or should I bypass it? My inventory is full - do I drop some of the parts I'm carrying in hopes of building something useful down the line, or sacrifice some of my limited food, ammo, or extra weapons?
Since I mentioned it above, a note on crafting. As you explore, you will find recipes and blueprints (or, sometimes, discover them yourself) that allow you to combine items you find to create new items. Some of these are intuitive (cook raw meat to make cooked meat. Combine certain meat with bread to make a sandwich, etc.) but the crafting system is very involved, to the point of being able to craft for yourself armor, weapons, and equipment that will drastically improve your chances for survival. How involved? Well, I'm several HUNDRED hours into the gameplay, and still am constantly finding new clues and recipes... it's certainly a rich and rewarding ara to explore -though sometimes frustrating, as the random nature of the game means you may have a great blueprint, but be short of a needed item to build what you want, and unable to find said item (or, worse sometimes, have all the items you need, but lack a workstation to assemble it!) The limited inventory space means you can't simply carry everything - you have to decide what is important to you, which again leads to some interesting choices sometimes. Anyway, know that crafting is very important in this game, and there's much to discover here!
(Also, note that I play The Pit with several DLC installed; this does add some to the crafting, but to be fair, I don't think I'm close to finding all the recipes from the original game yet!)
Your first choice when you begin a game is which character you'd like to play. The original game provides three options - a marine, who is very capable in combat but lacking in the finesse and scientific skills; an engineer who has lots of technical know-how but limited combat effectiveness; or a scout - a sort of jack-of-all-trades character, a mix of some finesse and technical skills combined with some light combat skills as well.
Available DLC (downloadable content) allows you to broaden this class list: Mind Games adds psionic powers to the game and allows you to play as a human Scion or an alien Tarka Ranger, and the Gold expansion adds four more (three immediately and one unlockable) characters.
I won't go into too much character detail here - the info is out there if you choose, but suffice it to say that each character has strengths and weaknesses, different starting equipment and skills, as well as a personal backstory for why the character is descending into The Pit.
And the choices you make are very relevant, too - for example, the marine excels at combat, so you'd think he'd be easy to play, as monsters don't really scare him. However, his lack of foraging skills mean he's more likely to go hungry from not finding food, and he may run out of ammo faster from not being able to find more - plus his limited science skills mean he's less able to craft new equipment for himself.
Overall, most of the classes are well balanced - there's one I find to be a touch overpowered, and a couple I don't play because they don't fit my playstyle (one in particular seems a little weak) but with this much to choose from it seems to me that the average player is going to find at least a couple they really enjoy.
Your character has four attributes (might, finesse, brains, and power) that you can increase as you advance, as well as various skills. Skills include weapons skills (pistol, rifle, blade, to name a few) and equally important non-combat skills (foraging, lockpicking, psionic skills, decipher, electronics, etc). The basic game has something like 20 skill areas available to your character, and the mindgame expansion adds five more (five different psionic skills) for a total of 25. Each time you gain a level, you're given a number of skill points (dependant on character class) to assign. Again, it comes down to choice - you can't be good at everything, so what's important to you? Skills will level with use to a certain point - but to be really good takes some added skill points.
Your character also has various other values (hit points, armor, etc) that are fairly self-evident, but I do want to make note of the hunger mechanism. Each character has a 'food' bar, similar to a life/hit points bar- eat some food, this goes up to a certain maximum.