What mood is created by the scenes on the castle platform in "Hamlet"?
W.H. Auden famously said that "first things in Shakespeare are always important". If you remember that the Globe Theatre probably wouldn't have had any (or if any, very minimal) scenery, it was very important to establish in the audience's mind what sort of scene they were suppoed to be imagining.
So what sort of information does Shakespeare give us?
BERNARDO: Who's there?
FRANCISCO: Nay, answer me. Stand and unfold yourself.
First thing: it's dark. Bernardo and Francisco, although onstage together, cannot see each other.
BERNARDO: ...'tis now struck twelve. Get thee to bed, Francisco.
FRANCISCO: For this relief much thanks. 'tis bitter cold,
And I am sick at heart.
Second thing - it's midnight (the witching hour!) and it is extremely cold, the time that these soldiers should be in bed. And finally, the watch has been very quiet: not a mouse stirring. Midnight, pitch black, freezing cold, and silent. That's a pretty creepy atmosphere from which a ghost can appear! And that information is all in the first ten lines of the scene.
You can do just the same thing with the next battlement scene. I'll leave that one to you: but have a look at the first line:
HAMLET: The air bites shrewdly; it is very cold.