This game is a flawed gem. It's definitely unpolished, but unique and interesting in it's own way. If you're looking for a really smoooth, AAA title, you might want to look elsewhere, but I had a lot of fun with Salvation.
The game is basically a war game. You choose to play as a soldier in one of four factions, but the gameplay structure is the same for all four. Starting out in a space station that functions as a shop / hangar / communication hub, you get missions that fall in to one of two types: on foot, or in space. The "on foot" missions are pretty simplistic third person shooting sections where you run around a field and blow up buildings and enemies. Each race has three weapons: a melee weapon, a ranged weapon, and a special weapon (like an energy shield or a bomb launcher). Space missions put you in the cockpit of your space fighter, and generally play like a simplified version of a space shooter, similar to something like Rogue Squadron or Strike Suit Zero.
The game is technically open world in that you can go anywhere, land on any planet and walk around, but since there's a war happening in real-time in the background, there's not a lot of time to explore. Completing missions gets you rank points (which give you promotions to advance your career) and money, which you use to upgrade your gear for the "on foot" sections and your spaceship. You can also get skill points to level up your character. However, there isn't a lot of customization here. Each faction has only one character model, which you can't change (humans can choose a few different skin tones), and one spaceship model, which also never changes. You can't even change your name, as far as I could find, even though it's just a text string. And while you can level up your character, you'll generally get all the upgrades in the game in one playthrough. This isn't inherently a bad thing, just bear in mind that you won't be able to, say, play a stealthy commando one run and a patient sniper the next or anything.
Moment to moment gameplay tends to be pretty shallow. The "on foot" sections are pretty straightforward, just move the cursor over the enemy, hold the trigger, and use a healing item when you get low on health. Space combat is pretty similar, although movement is slightly more complicated, you're still just pounding on enemy shields and popping a shield recharging item when yours get low. Annoyingly, enemies also get health/shield restoring items, meaning that a lot of fights tend to be drawn out affairs where you beat an enemy down to five or ten percent health and he pops a potion and heals back to 100, so you beat him down to five or ten percent again and he pops a potion and heals back to 100, so you beat him down again, and so on, until he runs out of regen items. It's pretty basic stuff, but it does get the job done.
Once you get to max rank, you become your faction's leader, and can direct where you want attacks to focus on, as well as what buildings to build on colonies and so on. This isn't as game changing as it sounds, though, because you can't really control if you win or lose a battle except by going there and killing everyone yourself, and since you can't have more than one attack going at once, you may as well join in on the battle anyway. However, enemies can still attack your bases while you're out, so progress tends to be irregular. You may get back from conquering one planet only to find you've lost two somewhere else. Or, sometimes, none, since the AI's decision making seems to be random instead of adhering to a specific strategy or anything. The endgame does get a bit annoying, too. Story events basically negate the progress you made in the game up to that point, and the challenge ramps up, except "challenge" in this game means massive waves of enemies with titanic health pools that take forever to burn through.
But I don't want to exaggerate the negatives, this game is a lot of fun, especially early on. You advance in rank fast, earning new abilities and upgrades fairly quickly, but never so quickly that you feel overwhelmed. The UI is clunky and ugly, but straightforward and easy to learn. And one of the really great things this game does is gives a sense of scale: you're usually going in to combat with 20 other allies, so you feel like a small part of a large team, rather than some unbeatable lone wolf, which is a neat feeling. On those occasions when you do have to do something solo, that aspect always made it feel special to me, making that jump without a swarm of allies around me felt more dramatic and tense because of their absence.
In terms of graphics and sound, this game is pretty inconsistent, as indie titles often are. There are a few good bits, a lot of the models look fairly nice. But as a whole, the art direction is hit and miss, there are issues with lighting and materials, the environments are very low detail, and so on. Outer space is full of asteroids and fights take place at point-blank range, making the galaxy feel small and cramped, while ground fighting is almost all on a slightly hilly outdoor map with few decorations or geological features making it feel barren and empty. The UI, as I mentioned above, is functional, but clunky to use (especially if you have to use it in combat) requiring a lot of extra clicks and wasting a lot of space. Animations are inconsistent, with some of them being fairly good (the sexy swagger of a Salvation officer) some of them being really bad (the derpy run cycle of a Drone Unity soldier) and a lot of them being flat out missing (like any kind of forward diagonal movement animation, your character just animates like he's running straight forward and drifts to the side). The audio is serviceable, but doesn't really stand out. The game does run at a nice framerate, though, and never crashed or ran in to any other technical problems during my playthrough.
Overall, this is almost a poster child for indie titles. The lacklustre graphics and shallow gameplay are made up for by the fact that this game tries to produce an experience that's mostly fun and unique. It's full of issues that a larger studio could probably have fixed, but the quirky nature of it's core gameplay produces an experience that a more polished title probably wouldn't match. Overall, I can't recommend it to everyone, but I definitely had a lot of fun with this game.