What kind of pan (dark metal, shiny metal, glass...)?

The header for the question has limited characters. So you want to make questions as concise as possible. What you have for the header is adequate because it contains the main thing you are requesting. The body of your post is where you can go into more specifics. I don't believe there is a character limit for the body of any question that you post.

As to your questions: I have made this recipe in glass, dark non-stick, and shiny aluminum. The type of pan does not seem to make much of a difference for me. Because pans and ovens can perform so differently even among the same brand and model, most recipes will not specify what type of pan. No 2 persons will have the same pans and the same oven, so recipes are not going to have any of those specifics.

When it's a generic description, use what you have and adjust accordingly. For example, glass/pyrex does not conduct heat well or uniformly. But if that's what you have, you might need to adjust timing or rotate the pan to get even browning. You'll know how things go with your own equipment better than any recipe can anticipate. Just keep an eye on the brownies towards the end of estimated cooking time, and use your sense of smell for doneness.

I make this a lot and it works well in my non stick metal gold pan from Williams Sonoma.