She never names a drink
Vivian sits down and does not look at the menu. She says something like "I want something dark, like I shouldn't be drinking it", or "something creamy, but with teeth", or "make it smooth, surprise me". None of those is an order. Each one points at a mood, and your job is to hear which one.
Ten moods, sixteen bottles
Every drink resolves to one of ten moods: warm, bold, sweet, dark, floral, sharp, smooth, dangerous, forbidden, desperate. The bar stocks sixteen ingredients, from vodka and whiskey through St-Germain, Chambord, Kahlua, Midori and absinthe. The same bottle reads differently depending on what it is next to, so there is no lookup table to memorise — only a vocabulary to learn.
Three tries is the entire design
You get three attempts per night. That single constraint is what makes the game a game. With unlimited tries it becomes a brute-force exercise and the conversation stops mattering. With three, you have to actually listen, and a wasted guess costs something. Most nights that go wrong go wrong because someone stopped reading and started sampling.
Progression per person
Correct reads move her through seven tiers, from Bar Vibes up. Progress is tracked per character, so a bad night with one person does not undo work done with another. Escalation is earned by understanding someone rather than bought with repetition, which is the same principle running under CELLBLOCK from a completely different angle.