Thanks for checking it out in this early stage!
Not being “warmed up” is a great way to put it, haha. I think it’s related to a known bug in the version of Godot I was using that causes the game to freeze until it compiles shaders for the first time if they’re not cached (so the first time things like explosions or muzzle flash happen.) It’s a difficult bug to work on but I think newer versions of Godot might have fixed the issue, so I’ll try to get this working in an updated version.
Upgrades and more tank classes and vehicles are totally something I want to add! I think all of the options you listed would be great, especially helis!