It's fairly well established now that QR codes, well, kind of suck. Although lots of people own a smartphone or gadget with a scanner now, no-one really bothers to scan them -- that's if they know how to at all. Still, that doesn't mean smart uses of the technology should go unnoticed, just like Korean Emart's big 3D QR code.

If you walk past a Emart store during 23 hours of the day, you'll just see a pretty strange art installation. But visit when the sun is shining between 12 and 1 in the afternoon and you'll be presented with a giant QR discount code.

Emart uses these "shadow QR codes" as a way of bringing more business to the store at lunchtime, when it's at the quietest point of the day. Anyone who scans the code at this time is sent to a special discount page on the store's website, plus a coupon worth around $12.

It seems the quirky use of QR worked, because according to Springwise, Emart recorded a 25% rise in lunch-hour sales and a 58% increase in membership in the month after it installed these shadow codes.

But there's one glaring question: If it's a cloudy or rainy day, does this mean there are no deals?