Why do you think that the theme is not fitting?
It´s not just building a wall it´s about building your wall bigger so scaling it because the enemys scale too in size over the time of the game eventaly they can just walk over your wall if you are not scaling the size of your wall.
I hope i could explain from my point how we interpreted the Theme.
And thank you for your comment!
We hope that you had fun with the Game!!!