You can download the standard Pocket Tanks for free legally. It includes 45 weapons and full online/WiFi multiplayer capabilities. How to Play on PC
If you want to play Pocket Tanks on your modern computer, there are several official paths: Pocket Tanks Deluxe - Download pocket tanks deluxe 500 weapons pc free
As of recent updates, the game features over 400 unique weapons through various expansion packs. You can download the standard Pocket Tanks for free legally