This update tries to address a few of the issues raised by review comments, which was not my priority during development but it seems silly to keep getting the same comments! So you've now got a fire button and you can't drive through the houses.
We've also moved the game on with the inclusion of a very simple map mode, terrain height, and projectiles (and tanks actually) affected by gravity.
For the future:
The game map is intended to facilitate coordination and control of multiple different tanks, setting their destination for ai, etc.
We're also going to play around with providing turret control for the players tanks perhaps using touch to allow you to rotate a turret and alter the up/down (sure there's a technical term) of the gun.
Anyway, enjoy the new version.