That can mean several things. The first being the obvious, he thinks your attractive and wants to stare at you. Not to sound pessimsitic but it makes it alot worse if you have a large chest or a nice body in general. and How can you be sure he's a nice guy when you don't talk to him? You really can't. Don't assume any guy is a nice guy because that's how girls get in trouble. I'm not saying assume he's mean, but rather, don't make any assumptions. Learn the truth for yourself.
bubbleemogirl_._