I totally agree with Generatoror on the different points he raised. So I allow myself to put an opinion on another aspect. The construction, I think that some additional tools would be welcome.
So I'm thinking of a shortcut to upgrade an object directly to the highest possible level. It avoids spamming u for long minutes when rebuilding a ship from zero.
I also sometimes suffered from the lack of possibility to switch from build mode to upgrade mode without having to F5.
Otherwise, this little game is really fun to pass the time. The new XP x2 and PvP mode surpasses the old Duel mode, I hope it will continue to evolve in this direction, with better customizations, etc... Good luck with the rest.
Ps: Very good choice of avatar!