One of the most fun games I've seen here in a while. I liked the gameplay I liked the complexity of the upgrades, it gives you a lot to strive for. Nice graphics and action while not killing my old computer makes it altogether 5/5 for me.
Since the hellstones are calculated mathematically, maybe add a way of changing the color of each hellstone based on the calculation? Like have a formula plug it into the color for each one. Vote up if you like this idea.
I blocked out a wall with racks and a register when moving to a new city. I decided afterwards that I wanted to add a row and bought it behind the racks, This resulted in being stuck in build mode with no way to exit so I could move the racks. I decided to save and restart and try to move my ranks then. They got stuck in place and wouldn't move but then I couldn't put one back down. I tried to click on another rack and couldn't put that down either. I restarted and lost the racks and still can't move the third rack. :-/
I had to have a sit-down with one of my waitresses. Sorry, waitrons. She decided to spend a day walking into one table, depriving me of a waitron and a table. I told her that wasn't acceptable, mainly because it's insane.