It was a little hard to get in but game play was addictive. UI was fine but needs some refinement.
When you scale up your whole system gets screwed up because if you use all your money now you can't combine the production to sale because you can't buy belts.
Now there was 2 major things I would 100% change.
I would make the scaling part side by side so the first room you start does not change. I would still use the larger rooms for new levels though.
I would either make belts free and make their upgrade system apply all of them or make each part adjustable lengths with a max limit to length.
Overall it is a good game kinda like "Cookie Clicker" but in a much more better way.