My crush acts strangely; he is hot and cold, what does that mean?

Anonymous
So I have a crush on a guy in my class (I'm in uni)
It all started when I noticed that he was staring quite often at me, but I didn't know him back then so I ignored it and didn't pay much attention to it.

When we started gettin to know each other we would stare into each other's eyes deeply and not look away when we talk, like we really don't tear our eyes from each other; but I'm quite the shy type and I wanted to be lowkey about my feelings for him so I try to supress them as much as possible.

However, now that we are more or less "friend", I feel like his behavior is really odd: sometimes he is really close to me, he act playful and all he talks to me, he invade my personal space etc..
And others, he keep it short and just talks to me at few occasions (he does however answer to my question, even if they're not directed to him; he helps me and I do catvh him staring at me once or twice).

I have also figured that he acts differently with me than with other girls: he is really playful with other girls, he likes to "make fun" of them but in a nice way whereas with me he is really calm and he only throw some little jokes here and there, he acts really mature and I don't know it's hard to explain.

I know that he said that he find me cute but that we don't talk very often to his friend (he knows I have a crush on him) but whenever I try to start a conversation he seems like I don't know "distant" but not really.
My crush acts strangely; he is hot and cold, what does that mean?
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