Why is it that I can hyperfocous when it's the computer and be under-focused when it's other stuff, even other stuff I enjoy, like reading, and watching movies...

Because the computer is interactive/self-directed/goal-directed?

I know that with the computer I get so hyperfocused that I'm oblivious to the world around me. I could be sneaked up on and I wouldn't even know it's that bad. But when it comes to school (even with my fav classes), I can't seem to focus for ****