Can you help me in my grumpy x sunshine situation?

Hi everyone, I hope you can help me.
I've been working for about 8 months in an all male environment, I'm the only girl. One of my colleagues, who is my age (22), immediately interested me. He is very very shy with girls, I don't think he's ever had one and I don't think he's ever had female friends either. Other colleagues told me that sometimes he received proposals from girls and simply did nothing, he avoided them. (I'm sure he's not gay)
I don't know if you know grumpy x sunshine, but that's exactly our situation. I am super sunny, chatty, funny and open minded. He is shy, lonely, distrustful and sarcastic. And that's exactly what I like about him, he seems so mysterious and I want to know what's on his mind.
We don't talk much, he avoids more private conversations, we can only talk about jokes and superficial topics. With my colleagues he talks more than me, but he never opens up to them even though they have known each other for many years. He's wary and I told him so. He smiled, as if I understood it.
Everyone understood that I like him and make fun of us for it, but both he and I play along. Sometimes he seems totally absent, other times he teases and annoys me if I don't listen to him. Often if I'm funny he tries to hide his expressions and laughs, but when I point it out he can't resist and bursts out laughing.
sometimes he makes fun of my clothing or some of my behaviors, but he is never offensive.
I don't understand what his behaviors mean. I don't think he totally likes me because I think he would have made some more obvious moves, but I don't think I'm indifferent to him. Sometimes I think he's influenced by all the other male colleagues who yes, love me, but joke about my feelings for him.
Help, how do I build a relationship with such a complicated person?
How can I get him to trust me?
How can I flirt without scaring him?
Can you help me in my grumpy x sunshine situation?
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