Thank you so much for your detailed feedback - I know it takes time to write so I really do appreciate it.
I recently started on the Art of Game Design but haven't gotten that far into it yet. Very interesting game design challenge, I'm looking forward to reading more.
Holding the speed control button is a great idea.
And yes, I can't tell you how disappointed I was in myself when I ran out of time to do something more meaningful with the score! 30 more minutes and I would've had a "Your high score: " above the total; a few more hours, I would have had a leaderboard; an extra day, I would have had a couple more levels (different building layouts) you could only unlock if you met each one's target price. I thought the game was a total failure without a use for the score, until the first few positive comments started coming through and lifted my spirits :,)
The good news is I'm planning to expand this into a full game, so it can get those features and more in its next iteration.
Thanks for playing, I'm looking forward to trying your game out too soon!