This game was so fun! Love tower defense games and just generally powerscaling so it was nice being able to save up enough gold to max everything out.
If you do intend on updating this game, I recommend maybe adding more depth to the connection system. Right now you can freely connect any gun to any upgrade as much as you'd want, but for example it could make sense if only a limited amount of guns could be connected to one node, or maybe connecting too many upgrades to one gun could cause negative synergies.