In 2013, nobody held their phone against a card reader. Contactless payment was not everyday life in Germany, it was a claim. At exactly that moment Deutsche Telekom built a wallet that could do all of it — with its own SIM card standard and a secure element holding the payment methods.
What I found was the real finding. Designs were made with small squared slips of paper with numbers on them. Every screen by hand, every time from scratch. That is not only tedious, it is error-prone: what is defined nowhere looks different the third time than the first.
So I built a complete UI kit. The design process in the scrum team became smooth — building blocks instead of handwork. The time this freed went into the micro-interactions. A payment product is delicate: whoever holds their phone to a terminal wants to know in that same second whether it worked. If the interface hesitates, trust hesitates.
