This was genuinely fun. The hints in the book took me a minute to figure out, and even then I had to experiment to see which combo did what before I could start making sales. I'm a bit ashamed to say my first playthrough very nearly tanked because I opened the store before I was ready. My only real complaint is the arrow buttons for switching screens. Half the time I clicked on them they didn't work, costing me a lot of sales late-game.
EDIT: Not sure if it matters, but the in-browser version is the one I played.