Some or any?

-In general, some (somebody, someone, something) is used in positive sentences:
I bought some flowers,

and any in negative and interrogative sentences:
I didn't buy any flowers / Have you got any luggage?

-But in questions, when we expect the answer is yes, we use some:
What's wrong? Have you got something in your eye?

-Also when we offer things:
Would you like something to drink?

-And when we ask for things:
Can I have some sugar, please?

-In affirmative sentences any can be used with the meaning of "it doesn't matter which":
You can catch any bus. They all go to the centre.

-Compare:
-I'm starving. I want something to eat.
-OK, what do you want?
-Anything.