Thank you very much for your comment~
This is a great development direction, and we will try to include it in the next version. We may add features like increasing health, repair speed, possibly boosting energy accumulation, enhancing shields, armor, and more. If you have other upgrade suggestions for strengthening the castle, please let us know.
If you have any thoughts or feel there are other problems, please let us know too. We hope this game brings you a bit of joy:)
We are truly appreciative of your feedback!