Not sure if this will be fun to play with, so an option to turn it off might be good.
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This game currently does not simulate the uneven demand over the day from customers.
In a store I have worked in (irl) I noticed that most customers showed up in waves, usually in 3 waves per day: Morning (about 8:00 - 9:00), lunch (12:00 - 12:00) & evening (16:00 - 17:00). with like a +/- 1 hour random variation, during monday - friday (wasn't open during the weekends, so don't know then, probably a higher & more even demand then).
This fluctuations comes from most of the population being at work, and goes to the store either: before work, during lunch-break & after work.
But a small part of the unemployed population (kids, seniors, sick, unemployed & those who take time off from work) still comes to the shop during the "low demand" times, so it's rarely no customers at all in the store.
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This variation puts a higher demand on the player to keep a larger stock of items to be available to the customer (you will need to increase or remove the purchase limit for this).
I guess this variation also needs a queueing system, to show the amount of customers waiting to be served.
But preferably avoid the "anger system" that most games use in these kind of scenarios, most customers are very understanding about it taking time, at least as long as you’re actively working on doing your job.
For example, if you fell asleep, most customers would rightfully be annoyed. But not when working.
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It would be fun to try this kind of variation of the game too in the demo.