"When I said 'engrossed' it seemed that it was somehow different than what Redhead23 said about 'blocking', but maybe they're just different views of the same thing? I mean, you would have to 'block' certain inputs in order to pay relatively more attention to something else, wouldn't you?"
Where did I say anything about blocking?
I don't think hyperfocussing is a conscious
As far as obsessing vs. hyperfocussing is concerned,
AFAIK hyperfocussing is when you are actually *doing* something (e.g. reading, thinking about something, playing a game, working on a hobby) at the exclusion of everything else (as in "being unaware of anything else), you hyperfocus on a given task or action, but it's more of a temporary thing (although many have certain things they know they hyperfocus on whenever they do them), e.g. you are hyperfocussing on a book that "sucked you in" and forget the time, but once you finished the book or put it down because you are tired, you are not still "stuck" on reading.
Obsessing is more *intrusive* and relates more to "not being able to stop thinking about something while you are doing [or meant to be doing] something else".
Hyperfocussing is more "being lost in thought about something, unaware of your surroundings", it can be daydreaming or staring at a pretty thing or playing a game and not hearing your Mom calling you for dinner.
Obsessing is being sat at the dinner table and not being able to talk about anything other than your obsession (or refusing to eat not because you are unaware of it being dinner time but because you "can't stop" playing), or trying to get to sleep and not being able to sleep because you can't stop thinking about something.
Of course if you hyperfocus on something for a long time (esp. if it is a negative thought) it can become "obsessing" but hyperfocus as and of itself is not a conscious or deliberate thing (although it can be welcome in many situations) and relates more to a "one-off" event (even if that lasts hours) than to a more permanent theme like with obsessions.
but if so that's like hyperfocus, except I think hyperfocus is more like getting 'engrossed' or 'driven' to 'un'distraction. To stretch the skating analogy further, the distracking-retracking of ADD can go on just like in skating-- all the time, so imagine your thoughts streaking along and then * there's a dis-track-tion and then ** there's another and then maybe *********** there's a longer one. So, don't be thinking too much about how nice it would be on that south sea isle away from the daily grind while you're doing the daily grind, well too***********much! 
Linear Mode
