What does it mean when a guy waits to respond to messages?

Anonymous
There's a guy I've known for many years that I'm interested in and he's generally very hesitant with initiating contact with other people. Recently, he messaged me out of the blue, something he rarely ever does, and since then we've been messaging back and forth everyday.

But there's one thing I've noticed that's confusing me. With the messaging system we use, it indicates whether the last message I sent was read or not. Usually, he reads the messages within the hour, but he always waits a few hours before he replies. And just 2 days ago, I replied to his question and asked back a similar one. He read the message right away, but still hasn't responded.

Does this mean anything? Was he ever interested? If so, has he already lost interest? I know lots of girls play hard to get, do guys do it too?
What does it mean when a guy waits to respond to messages?
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