We have all seen QR code implementations before. But one based on time of the day and shadows?
This innovative use of QR marketing is developed and use in Seoul for a retailer. Consumers are rewarded discounts at quieter times of the day, in this case between noon and 1pm.
http://www.springwise.com/retail/seoul-retailer-3d-qr-codes-sun-deliver-discounts-quiet-times/
