ZDF’s media library is one product that has to behave like five. The same content and the same functions run on a phone on the train, a desktop browser at a desk, a TV from the couch, an Android TV app and HbbTV on a broadcast-connected set. Each of these is a different interaction context, not just a different screen size.

DetLines was the design system phase of a longer collaboration with ZDF, about three years in total. The phase itself ran roughly three months and I was involved from the start. The cross-platform span was not a technical footnote. It was the design problem.

My core method was direct: take one function, capture it on every device, and compare.

I picked a function and went through each platform with it. Mobile, desktop, TV, Android TV, HbbTV. Screenshots, placed side by side. Then I documented what existed, what was missing and where the behaviour diverged. Differences that were hard to see inside each platform became obvious in one shared row.

I took every round of findings into the next client call with ZDF: what diverged, what was missing, what needed to be aligned across platforms. The open topics moved into the backlog.

The rule that came out of these comparisons: consistency means the same underlying logic, adapted to device, input and situation. Not the same screen everywhere.

A TV surface keeps the logic and changes the expression: fewer elements, larger type, targets that work from the couch with a remote. A mobile surface keeps the logic and reduces the information to what the situation allows. The function stays recognisable. The form follows the context.