I don't know the exact definition of an idea being started on, so yeah... I'd say it's fine. If you had build a prototype, that would have definitely crossed th

I don't know the exact definition of an idea being started on, so yeah... I'd say it's fine. If you had build a prototype, that would have definitely crossed the line. But you don't even have a landing page up, right? I have only been to one (in Berlin) before, and there have been a couple of pitches where people did spend time previously researching. It's fine with me, if you are willing to leave some creative freedom and not force everything pixel-specific onto people.