Tank Riders from Polarbit Games is a pretty decent top down tank shooter with some strategic gameplay elements. The graphics and sound are well done, and the game can be great fun, but clunky controls and a myriad of bugs and issues really bring the experience down. Still, it may be worth looking into if this kind of game appeals to you.
The game features a single player campaign with 30 missions split up between two chapters and a tutorial section. Missions basically consist of roaming around a level and stepping on or shooting switches to lower gates, or using teleporters to get around. Along the way, various enemy tanks will impede your progress. There are plenty of destructible boxes with collectible goods, secret paths, and some cool power ups to keep things interesting. Weapons range from your normal canon, to a very useful mortar, an upgraded cannon that shoots bouncing projectiles, and the ridiculously overpowered missile launcher. It may be overpowered, but it doesn't come along often. It's a blast when it does. Levels are rated out of three stars based on your performance, tracking things like accuracy and completion time.
The rather blocky campaign levels were pretty well designed, and I would have enjoyed them the entire time if not for other issues. You play the game by moving with the left stick and tapping in the direction you want to shoot. This can lead to some problems, as it's hard to strafe and dodge enemy fire while your fingers obstruct your view of the screen. You can change the control options to utilize two sticks, but the new firing stick is really wonky and also kind of hard to use. There's a multiplayer mode, but you'll have to register an account to use it. Not only is this annoying, especially because the keyboard they make you use is not the standard iPhone keyboard, it wouldn't even work for me no matter what I did.
The blocky graphics are sharp and the colors are vibrant. The music is also surprisingly very good. There are in game achievements to nab and leaderboards to climb if you can get online. The game also froze and crashed on me way too often in the short amount of time I played it. It's a pretty decent game if you're really into the arcade style gameplay, but otherwise you should probably hold off on this one until it's fixed. You can download this iOS Universal game for two dollars.