With scan-n-go, your smart phone is to scan the bar code on all your purchases as you walk thru, then at the end, you tap "checkout", it gives you your total, and you have a button to "slide and pay" so the entire transaction goes to the card stored in the app. A QR code shows on your screen to confirm successful payment. Then just walk out the door. Yeah, that big arch gets excited if there's some type of error or mis-click. And, if you've bought alcohol, the QR thing on your screen after paying is red instead of black, and you're stopped to confirm you're over 21.