There are some pretty clever guys out there in South-Korea! Emart, a Korean retailer market invented shadow QR-Codes, a marketing gag which allows people on the street to capture QR codes which are only visible at lunchtime, when the sun shines in a specific angle on the installation. According to the video in the source they could raise the conversion rate during their "sunny sale" enormously. I wonder when we will see something innovative in Austria.