flowchart TD
    cart([Customer opens the cart]) --> stock{All in stock?}
    stock -- No --> backorder[Offer a backorder]
    stock -- Yes --> address[Confirm the address]
    backorder --> address
    address --> pay[Charge the card]
    pay --> paid{Approved?}
    paid -- No --> retry[Ask for another card]
    retry --> pay
    paid -- Yes --> order[(Save the order)]
    order --> email[Email a receipt]
    order --> warehouse[Queue for packing]
    email --> done([Order placed])
    warehouse --> done