Did you write everything correctly and fully. Seems like something is missing. App can be food, software application, or job application. However, I would assume food since it says “casual black tie feel.” “A casual black tie feel” means that the event did in the past, does in the present, or will in be the future an event that’s between casual and sophisticated. From the context, there’s no indication of tense. Sometimes, in order to provide someone with a description of what to expect we will say ____ feel: (give you that ____ feeling). Casual/Black tie feel: a somewhat casual but also sophisticated event