engrossed
So focused on something that you ignore everything else.
Engrossed describes being so completely absorbed and focused on something that everything else fades away. If you're engrossed in a thrilling book, you might not hear your parent calling you for dinner. When a scientist becomes engrossed in solving a difficult problem, hours can pass without them noticing.
The word suggests a level of concentration where you're pulled in so deeply that the activity captures your whole mind. A chess player might become engrossed in finding the perfect move, studying the board so intently that they forget the crowd watching. Students sometimes get engrossed in building an elaborate project, losing track of time as they work.
Engrossed describes that wonderful state when you care so much about what you're doing that distractions disappear. You might become engrossed in writing a story, practicing a musical instrument, or even watching an exciting movie. It's the feeling of being completely inside an experience, where nothing else seems to exist for those moments.