One day, he smiles & give attention to me. Another day, he completely ignores me, what does it mean?

So there is this guy in my class, he is my crush, i feel like even he has a crush on me. But someday he smiles at me, gives me lots of attention, talks with me and the other day he completely ignores me.
what does that mean? this is so confusing!
is he playing hard-to-get? or not interested in me?
please help me out with your opinions!
One day, he smiles & give attention to me. Another day, he completely ignores me, what does it mean?
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