Revolutionizing the cash register receipt sounds like the worst kind of startup cliché, but indulge me for a moment. On Tuesday, Square unveiled a new feature for its digital receipts that, in and of itself, doesn’t radically change how we interact with the places where we shop. But it points us in this direction. And it starts with a smiley face. Square is best known for its new-age credit-card readers, which plug into the headphone jack on a smartphone or tablet. It’s pretty cool, but for the merchants of the world, the meat and potatoes is Square’s Register app. One of Register’s basic features is the ability to send electronic receipts. The first time you swipe a card on Register, you’re asked for an email address or SMS contact number so the merchant can send a receipt. Provide one, and every time you use that card, your contact info is right there, no matter where you are.