How do we describe an imaginary scenario? Do we use present, past or future tense?
Describing a non-factual situation to a someone
"Let's say, you are in a room, and someone comes in with a knife walking towards you. will you scream?"
or should it be
"Let's say, you were in a room, and someone came in with a knife, walking towards you, would you scream?"
I would not use a comma after 'say'.
In the first, I'd say, "; do you scream?" The second is fine.