How would you react if when you turned around I was staring at you?

I'd tell you you are welcome

I'll smile at you.

Considering there's a wall behind me, i'd be impressed

Take a step back and say "Wah your a ninja, or just very sneaky... Hmm"

i don't know, you're like; the least intimidating person on here.

I would offer to share my lunch with you😄

I'd just smile 😁

Ignore it