Phenomenal art direction, audio design, and polishing, but it felt like the rest of the game was somewhat lacking.
While it was fun to combine buildings into better buildings, it all felt a bit pointless as the buildings served no purpose. I understand the goal of the game is to place as many tiles as you can, but it would be nice if certain buildings affected the gameplay. Perhaps building the big castle could add a new empty tile to the edge of the 5x5 grid, or a water refinery could clear out neighboring corruption. The shield building seems to do something along those lines, but I never figured out what it does exactly.
I understand this is a jam game, so I completely agree with your decision to limit the scope and focus on polishing the core gameplay loop, but it all falls a bit short in my opinion.
Additionally, the goal of the game is to place as many tiles as you can without any real win condition. It feels pretty bad to be greeted by 'Gameover' in big red letters after every game, even when you beat your personal best. Instead you could have used 'Results', or 'Your performance'.
The concept has potential to be a lot of fun, but I feel like you were just a bit short of reaching that point. Currently all the fun comes from the tiny dopamine rush of combining things and seeing the result, but that feeling fades away very quickly.