Typically I think of tower defense games as a cycle: build your towers, wait to money to accumulate, build or upgrade more towers, wait for more money, rinse and repeat until the level is finished. It's possible to play Sol Survivor that way, but you will lose. The key to victory in Sol Survivor isn't just you tower defenses, but also a wide selection of support abilities. There are 19 diverse support abilities in all, ranging from orbital lasers and mines to more eccentric tools like poison gas and tornadoes. The towers are still your primary means of defense for most situations, and they have a healthy variety of their own, but the support abilities are a welcome addition to the genre allowing you to take a more active role in the battlefield than other tower defense games. It completely changes the way you play and strategize in a very refreshing way.

Of course, as with most strategy games, Sol Survivor really shines brightest in the multiplayer department. There are five multiplayer modes to choose from: Versus, Cooperative, Co-op Campaign, Duo Campaign, and Wars. The Versus mode puts you and up to 7 other players, in teams or individually, against the same set of foes in a contest to see who can last the longest. Cooperative mode puts players into teams and gives each member of the team a section of the map to defend. Both Versus and Cooperative modes feature unique maps designed specifically for that game type, which can be a bit annoying if you find a favorite map or two in one mode and want to use them elsewhere, but the levels are well balanced and fit the mode they are used in. Next up is the Co-op Campaign and Duo Campaign modes, which give you access to all 20 single player campaign missions for multiplayer use. Co-op Campaign is for up to four players, with each additional player making the enemies you face that much stronger. Meanwhile Duo Campaign is for just two players, putting one player in charge of tower building while the other handles support abilities. Duo Campaign will probably get the least amount of play time since the support abilities don't stand on their own as well as the tower defense part of the game, but works well as a way to allow action fans and strategy gamers to play together in a unique way. And then there's the last multiplayer mode...

The Wars mode is so spectacular that it deserves mention independent of the standard multiplayer offerings. It takes the action/tower defense gameplay of the other modes, and adds an RTS element on top of it. So not only are you and up to five other players building towers and launching support, but you're also in control of sending enemies for your opponents to defend against. Since you'll be buying both towers and creatures, an income has been added to help you afford all of the units. Balancing your income becomes a game in and of itself. If you build more towers you'll have a higher upkeep, which takes away from your income. On the other hand, sending creeps at your opponents will increase your bounty, which earns you a higher income. All of this keeps the Wars matches very focused on offense, which works surprisingly well in a tower defense game.

In case you couldn't tell, I absolutely love Sol Survivor's multiplayer modes. However there is one fairly major problem with playing online: there's hardly anyone else to play against. I almost feel bad including this aspect in my review because it's really an element that is out of the game's, and the developer's, control. And to their credit, the developers have been great about arranging community playtimes where the dev staff will be online, ensuring that there will be someone to play against. But they can't be on all of the time, and when they aren't the multiplayer lobbies are pretty barren. On Steam there is a Sol Survivor community group that helps in organizing matches, and it helps, but still isn't perfect. Considering that the multiplayer is such a strong part of the Sol Survivor package, the lack of people to actually play against is a little disappointing.

But that isn't to say that multiplayer is the only way to enjoy Sol Survivor. The single player campaign is quite long, with several difficulty levels for added replay value. All told there are 10 different officers to control (available from the get-go in multiplayer or gradually unlocked in single player) and each one has a unique loadout of towers and support at their disposal. No two officers play alike, so it's actually a fun and fresh experience going back and playing the single player campaign with a different officer. There are also badges to strive for, which are specific level challenges separate from the Steam achievements. These badges could range from beating a level with every officer, to only spending a certain amount of money on towers, or defeating a majority of enemies with support rather than towers. But these level badges are only available on the higher difficulty settings, so it seems that they're more in place as an extra challenge once you've well familiarized yourself with the game and beaten it once. Additionally, as you make your way through the single player campaign you will advance your rank and unlock new tower upgrade levels. You can then go back to previously completed missions with those tower upgrades to get some of those badges you may not have been able to get the first time around. And in case you needed even more gameplay, there is also a Survival mode featuring five additional maps with their own online leaderboards and badges.

So what exactly is different between the PC and 360 versions of Sol Survivor? The 360's radial menus for selecting towers and support return, which were an excellent solution for the game on a console controller but aren't quite as tailored to PC play. To make the controls more PC-friendly there are also now HUD icons as well as customizable hot keys for access to all of your towers and support. And if you do happen to prefer using a controller over mouse and keyboard, Sol Survivor still supports Windows compatible Xbox 360 controllers. The graphics seem to have received a slight upgrade, though they were already nice to begin with whether zoomed in on the action or from a high bird's eye view. Menus and other art such as character portraits, on the other hand, have all received HD makeovers over the 360 version. Also new for the PC version are all of those badges mentioned in the above paragraph that add so much replay value, as well as an additional difficulty setting for expert players. The biggest enhancement though is the post-release support. The folks over at Cadenza have been excellent about constantly improving their game based on their own development plans and user feedback. This includes six new multiplayer maps, the Co-op Campaign multiplayer mode (also not found in the Xbox 360 version), and a colorblind option to make the game playable for everyone. Not to mention that there is even more of a "where did everybody go?" effect for multiplayer in the 360 version without community groups, so the PC version is really the way to go.

I'm just going to go ahead and say that Sol Survivor is the best tower defense game I've yet to play. Between the unique officers and the way both towers and support abilities are used, the strategic options are rich and rewarding in ways that I haven't seen from the tower defense genre before. It says something strong about the game's quality that the only real fault of the game is outside of the game itself. Unfortunately, it's a pretty big downside. The single player campaign is still more than fun enough to easily justify Sol Survivor's $10 price tag, so if you're a fan of single player strategy then this one's a no brainer. That doesn't mean that gamers who have their sights set only on multiplayer should pass up Sol Survivor, seeing as it offers some of the best and most unique multiplayer that the genre has to offer. But if multiplayer is your thing, then hopefully you have some strategy gamer friends that can download the game along with you.