Thanks for the feedback! Much appreciated.
The effects of upgrades are barely noticeable right now. But they're set up like this:
Wings - Increase turret rotation speed
Engines - Increase speed
Guns - Increase fire rate, fire speed, fire power
Cockpits - Does nothing now, but the idea is to increase the fire range
The copper, silver, gold "things" do nothing ; ( I thought perhaps adding a "fuel" or "energy" level that is refilled by those "things". But I want to polish the basic gameplay instead of adding more features.
Do you think the next step should be to improve the upgrades system?