Guys - what do these signs mean? Girls opinions okay too.?

Okay so there's this guy I really like and we're both about 18. We've gotten to be really good friends over the past few months. He told me he likes this girl and how he subtly asks her out but nothing ever happens. Lately I caught him looking at me a bit but I thought I was over reacting. Then this weekend in a reply to a message I'd sent him he asked me what I was up to that night. I said nothing much. To which he said "if that's a regular occurrence maybe we need to get you out with me". Then I said "that would be really fun" and he didn't reply. The next day at school it seemed like he was avoiding me a little, didn't look at me, walking alternate routes to cl etc. Then he did the strangest thing, he started being real immature and was playing 'mission impossible' trying to p through the corridor where I was waiting undetected by me - but I saw him and he got embarred, laughed and ran off. He then went and talked to the other girl (the one he said he likes and is also good friends with) and her friend for a while and then they all walked out of the room smiling and he came and sat and talked to me like we always do. My question is: what's he most likely thinking/feeling and what does all this erratic behaviour all mean? I know he's not a player and he's not being nasty. He is seriously the nicest guy so I don't think he's using me as a replacement for the other girl. But does he think of me as a friend, or does he like me, or is he having me on? And if you think he does like me, how can I get things moving here? Thank you so much!