On Pocket Tanks site they say:
The fastest game of artillery you’ll ever play. Pocket Tanks is designed to be easy to learn, and fun to master. All the excitement of lobbing projectiles over a mound of dirt without all the complicated details found in most artillery games. Select your angle, power, and fire over 30 distinct weapons at your opponent. There is an innovative Weapon Shop to keep the game moving fast and a Target Practice mode for experimenting with all the weapons “no holds barred!”

Its Shareware But you can try to download it on bellow link