The demo worked. Now give it to someone else.
I like prototypes because they interrupt convincing conversations with something we can actually try.
Then I watch someone use it—ideally without explaining where to click. That part can be uncomfortable. Especially when they ignore the feature I spent the most time polishing.
Their hesitation often tells me more than their compliments. What did they expect? Where did they lose confidence? Did they understand the result?
I try to decide what we need to learn before building the prototype. A sketch may answer a navigation question. A technical experiment may reveal an integration problem. Neither necessarily needs a login page, a settings panel and our final choice of font.
Although choosing the font is an excellent way to avoid the difficult questions.