OK question? If a guy flirts, makes long eye contacts, always greets me in the morning when passes my workplace and says Bye when leaves (exclusively for me) etc., one day and then after a couple of days like I'm not there, no Hi (not even a glance) in the morning, ignoring during day etc. It means he just wants to flirt on his conditions and nothing more? And we kinda were starting to hit very good lately, so that's why I was wondering what happened?
Playing games. Maybe he's trying to gauge your interest in him, and wants to see your reaction if he doesn't flirt. And see? This is your reaction. :) Don't give into him. Give him a week or so, don't react to it. If he becomes friendly again then be friendly with him. But not until then.
I just wanted to add that he could also be suddenly paranoid of rejection. I have a coworker who did the same exact flirt and ignore once the girl is interested. She ended up pursuing him anyways, and now they're together. But if you ask me, it sounds like he is a bit immature and has ego issues.
Funny...same exact thing just happened to me, and I was wondering the same thing. Could it be that he is suddenly unavailable and met someone else? By any chance are you in a relationship and he is worried about pursuing you further so he just shut off?