Further notice - the app is running in fullscreen kiosk mode. No OS built-in text input methods are allowed, just screen touches.
First, customer touches the screen to exit the screensaver (NOT included in this contest) and goes though following screens:
1) VERIFY YOUR IDENTITY - this is done by entering your phone number via screen numpad, receiving one-time code via SMS and then typing the code.
2) SELECT PRODUCTS - customer selects which products he/she would like to buy and confirms.
3) SELECT PAYMENT METHOD - customer selects among several payment methods. Please note, that no payment method requires the customer to stay in the app (SMS with short link or push notification to separate app will be sent) - these are "click-and-forget" actions. Also, currently there are 3 methods (although sketches show only 2), but there might be room for more, but not too much - maybe 4 or 5.
4) NOTIFICATION TO COLLECT THE PRODUCTS - at this point vending machine opens for customer and he/she has chance to grab their stuff. This screen simply instructs users how to pick up the products and waits to be touched - this will close the machine.
5) GOODBYE MESSAGE - simple screen, which says farewell and returns back to screensaver after a while (or when touched).
** One notable suggestion - constantly let customer know on which step he is currently and how many step there are.
The screen is longside horizontal, shortside vertical.
SEE ATTACHED UI FLOW.