Great "build your base defenses" turn based strategy.
The combat in the game is very well-defined. Your units have a range, an attack strength, armor rating, number of attacks and number of hit points. When an opponent is in range, you fire. The amount of damage is attack minus armor equals damage. I know that sounds very simplistic. But I just can't tell you how frustrating it can be in other games where you can't figure out why your units do so little damage to the enemy.
In my mind, the really fun part of the game is building your base. You can built gun turrets, artillery turrets and missile turrets for defense against ground units. You can build anti aircraft turrets for defense against air units. Against sea units, well, you have to build a sea unit factory to crank out the corvettes that can detect submarines and other sea units to detect surface ships.
Each unit has a certain sight radius called 'SCAN'. One of the really fun things about the game is how the enemy will find a hole in your base defenses where you have a gap where the enemy can get close enough to damage your base defenses without being seen by your base defenses. In other words, you might have a gun turret that can fire much farther than it can see. Similarly, the enemy has missile turrets that can fire even farther than your gun turret. If you don't have your detection grid setup properly, then you may suddenly have an incoming missile destroying your base defenses without any idea where it came from.
All-in-all, it really is a fun little game that I continue coming back to play.
Unfortunately, the AI was really quite poor in the first version of the game. The developers "beefed up" the AI but at the cost of stability. Now, the game ALWAYS crashes after 'X' number of turns. Still, despite that horrendous problem, there really isn't another game like this out there.