1. You read obsessively about the game from all the game sites.
2. You read and re-read the walkthroughs regarding the parts that you get stuck.
3. You rant about not being able to kill the boss, everywhere.
4. Playing the game just before bedtime will make you dream of it. Everything, from boss fights to the monsters.
5. You go out and look for the soundtrack because, you know, the game isn't just enough.