At first glance, StormWinds appears to be a pretty typical survival shooter game -- you buy turrets, then waves of enemies attack, and you shoot them with your turrets. In between rounds, you have the chance to upgrade your turrets. Overall, it seems like a pretty standard formula, and I don't really find a generic survival shooter to be that entertaining. However, StormWinds adds enough details to the basic formula to make a pretty interesting game; it's a nice lesson in how carefully crafting the details of your design can really add a lot to a game.
Anyway, in StormWinds, you first craft your defense by laying out your turrets. You typically have four or five slots in which you can place turrets, and careful consideration is important here. Some turrets are designated primary weapons, which means that they have a high enough rate of fire to use more or less continuously, while some are secondary weapons, which can only be fired once every so often (but usually pack a punch when they do); there are also support turrets which passively do useful things for the other turrets. Being able to quickly switch between turrets (since you can only be firing one at a time) is an important skill; it also means that there's not much point in having more than one primary weapon, except perhaps as a backup. Careful positioning of turrets is also important; high turrets are useful against high-altitude bombers and to lob projectiles on enemies from above, while lower turrets can be useful for attacking the less-protected underbellies of enemy ships. Forward turrets are more exposed to damage, so you'll want to stick something there which can soak up a lot of fire, and so forth. Turrets come in a wide variety of different types of destruction, and are often operated differently: some turrets are as simple to use as clicking where you want to shoot, whereas others lob projectiles or even fire guided missiles; these latter types are harder to use but can be quite useful in certain situations.
Once you've built your defense, the enemy comes in. There's a wide variety of enemy types, and not all of them can simply be shot. Many enemies have strong or weak points, so careful aiming is important; later, you'll encounter enemies which may be entirely shielded from fire from one direction, so having guns that can hit them from unexpected angles is not only useful, but necessary. Your turrets will take damage as they are hit by the enemy, and it's not at all uncommon to end a wave with one or more turrets out of commission entirely (though, of course, if all of your turrets are disabled, then you lose), so you'll need to plan for this contingency. Between battles, you can repair your turrets, buy new turrets, sell your existing turrets, or upgrade your turrets. This last requires your turrets to gain experience (every kill grants experience to all turrets currently on the battlefield); as your turrets gain levels, you gain upgrade points to spend on an upgrade. This often creates a dilemma about whether you should spend your money to buy a shiny new powerful turret even though it starts at level 1 again, or hang on to your older turret which has already gained several levels.
The game offers five campaigns, each of which contains 10 successive waves. Overall the game moves quite quickly; unlike many survival shooters, which tend to be pretty slow (possibly because of the popularity of zombies), each wave is pretty fast-moving and also doesn't last very long, so it won't take you too long to make it through the campaigns. One occasional nuisance is that you may reach the later waves of a campaign and realize that the mix of turrets you've gone with simply doesn't work; this may require you to begin the campaign again from scratch. (Should you be defeated, however, you just begin again from the start of the wave, so you can also try different tactics to see if you have any better luck.) However, once you've figured out which turrets make the best combinations, the game is actually pretty easy; I breezed through the last campaign, which is supposed to be the hardest, without too much difficulty at all. In addition to the campaigns, there's also a few standalone challenges, which just consist of one (usually long) wave with some special properties.
Graphically, the game is very well-designed; the game has an overall steampunk aesthetic, and the individual ships, turrets, and backgrounds are all very well-crafted. The sound effects are a little repetitive, but they're also probably above average; the music is nicely martial, though, like so many games, it gets repetitive eventually. The interface is solid, although it seems like the hotkeys for selecting turrets change in different campaigns, which is a little annoying (although you can change the defaults).
Overall, StormWinds is a fun little game. It's probably a little bit too easy once you figure out an optimal strategy, although it can be quite tricky to figure that out, but it does a good job of keeping the action flowing. It probably won't take you a terribly long time to finish everything the game has to offer, but it's definitely a fun little challenge.