I am a fan of Defcon for PC and I was searching for similar game for my iDevice. I found Deftron by Sylvain Marsault as the perfect alternative for it.
Deftron is cold war themed game where the world is divided into continents-enemies (Africa, Europe, North America, South America, Asia, ussia) and your objective, as the game tutorial says, is to destroy enemy cities by launching Nuke missiles at them, while trying to protect your own. Destroying cities (killing citizens) increases your overall score while losing your own citizens decreases it.
The game is mainly in black blue and reminded me a little of the movie Tron. 
Main menu in blue and black..
When you launch the game and after the splash screen,you’ll see the main menu. Here you can start a new battle or resume a previous one, read the tutorial, see your stats and change the difficulty level.
I highly recommend to read the tutorial before starting a new battle because it provides a lot of info about the game mechanics and controls.
After tapping on “New Battle”, you must choose your continent and after that the other continents will join your game in a random order.
Calm before the storm.
First in game screen will be your first factory and your subs. Factories provide credits to you and must be protected at all times. You can capture an enemy factory by destroying the guarding enemy units.
On the bottom of the screen the left six button are for creating new units.
The left three icons are your naval units that spawn at your factory. To select a unit simply tap on it. To select more than one unit either tap on the “Square” button or tap on one and tap on it again to select the nearby units. To move them, tap on the “Arrow icon” and then tap on the destination.
Nuke incoming. You can see the air units above the center circle.
Next icon is your anti-aircraft unit that protects your territory from enemy bomber units and enemy nukes.will be placed at the center of the screen.
The next one is you bomber units that can be used to destroy enemy anti-aicraft or scout enemy territory. Move the center of the screen over an enemy AA or territory and then tap on the bomber icon to attack it or move to it.
Cairo was nuked. You can see the blue arrows that point to the incoming nukes.
The last icon is your nukes. Move the center of the screen over an enemy city and tap the nuke button. Nuking other cities is not available all the time. There’s a timer on the bottom of the screen, that informs you when nuking is prohibited and when it is allowed. When nukes are launched you can see in the center of the screen were they are and how far they are..
Alliances Screen.
An interesting feature is the ability to form alliances with other continents. Ally with them to destroy your enemies and break the alliance to destroy them!
Overall, the game is very good and you’ll like it if you are into this kind of deep strategy games. It is challenging and you have to think your every move. Even on Level 0 you can easily be destroyed if you don’t pay attention. Also, I have to mention that I haven’t experienced any crashes and it was running smooth all the time.
Compatible with iPhone, iPod touch, and iPad. Requires iOS 3.1 or later.
Availability: 
Rating: Not enough ratings received.
Price: $3.99
Reviewed at version: 1.0
Developed by: Sylvain Marsault
