The counter
This is what the barista sees. A real till scans the code on the pass. Here you get the card on this browser, or you can look one up by the code under its barcode. Punch it and the pass updates on the customer's phone.
This browser has no card yet. Get one on the home page, or look one up by its code above.
Redeeming resets a card to zero, so every card can go round again.