For under $10 it is surprisingly good
It is a simple game but very fun to play. It is a tower defense game and there is no workers or economy or resource buildings to worry about. But that does not mean you won't be busy! When you aren't throwing down defensive buildings or upgrading them you are using a variety of support abilities. These include raining down missiles or fire bombs or a disabling blast.
You might think it would get boring just building defenses and blasting the same bad guys over and over but there is enough variety to keep you on your toes. You play as an executive officer with a few turrets and support skills or you can customize your own. This gives you a lot of different ways to play the game. There are tons of badges and other achievements to collect which will give you new challenges on the same map. There is a good amount of depth to this game and any strategy addict will enjoy it.
Good: Cheap, I got it off Steam for $5, reg. price is $10 which is very cheap. High re-playability with 20 campaign missions, 5 survival mode levels and 3 difficulty levels. I found normal to be pretty easy but hard and intense modes to make it just challenging enough instead of frustrating like other games. There is co-op multiplayer as well although I haven't tried it.
Bad: I feel the graphics could be better and the effects mainly could be done better but this is a budget game. Sound gets repetitive and I didn't see any mods. No speed up button which makes the first minute boring but it speeds up very quickly after that.