If I was talking to someone face-to-face I would always be clear, but with something like Snapchat, you need to keep the flirty banter going;otherwise you'll be staring at an empty red arrow, cringing.
I think guys are afraid of being too straightforward, so sometimes being coy gets you nowhere.
I don't know any girls who appreciate getting a close-up snap of a guy's privates out of nowhere.
People need to be able take the hint on Snapchat, like in real life. If you're always the snapper and never the snappee, then maybe they're just not that into you.
