I posted this on another thread, but it's appropriate to post here as well
http://www.youtube.com/watch?v=eBSM82UO_cwThis is a proof of concept of a tank game I'm working on. This video is a few weeks old and there's a lot missing. For one thing, I hadn't written the collision detection between the enemy bullets and the tank.
I now have enemy turrets which follow your position. The tank has a shield which takes damage before the tank. And there's a health bar which shows your tank's health and shield strength. Also, the tank now has primary guns on the tank itself as well as the rocket from the turret.
The more I work on it the more I realize there is to do. To make this a playable game will take many months of focused development. (and much better artwork)