What are the signs a reserved Muslim guy is into you?

Salaam everyone,

There’s this guy I’ve been noticing for a while. We go to the same university, gym, and masjid. I've noticed he’s respectful, quiet, and doesn’t talk to girls. I finally had a reason to talk to him while volunteering for an event that needed interviews. I saw him after salah, tried to catch up, and he actually stopped when he noticed me. I said he walks fast, he smiled and apologized. The convo was short, I explained about the interviews, and he said he wasn’t comfortable but could ask around. We stood close and kept eye contact, which surprised me since he usually lowers his gaze. Two days later, I saw him at the library. I could feel his gaze, and when I looked, he literally hid behind the bookshelves. Later, he said salam to his friend group right next to mine, and that same day near the prayer room, we made eye contact again. He gave me half a smile and nodded, and I did too.

What are the signs that a reserved Muslim guy (the type who lowers his gaze, keeps things respectful, doesn’t flirt, and doesn’t even talk to girls) might be attracted to you when neither of you talk or have opposite-gender friends? When both people are trying to stay respectful and keep things halal, how can you even tell if there’s mutual interest or if he’s just being polite? For sisters who’ve experienced this, what were the small, subtle things you noticed? And for brothers, how do you usually show interest without crossing boundaries?