Perception

[Tastytango]

Name changed foe this. If over a long period If time someone gives you strong attraction signals but doesn't do anything about it the general thought is you imagined it. BUT I did not imagine it. Are they just playing with your mind

Not necessarily. They might fancy you but aren’t getting any signals that the feeling is reciprocated so aren't acting on it.

Agree with @DatingDinosaur
Did you give them any encouragement @Tastytango ?

I thought so, in that i responded but not overly flirty.

Maybe the other person hasn’t picked up on it? Or has, but is a bit shy with affairs of the heart.

If you like them, perhaps be a little more bold? Not necessarily ask them out but engage them in more conversation and try to be in their orbit a bit more. Make an effort to get to know them better the uncomplicated way.

Unless, of course, you know they’re married or something. In which case, do nothing and keep them at arm’s length in the friend/acquaintance zone.

If you're not actually interested and only flirted back because you've picked up that they like you and you enjoyed the interest then it's probably best not to build their hopes up.