obsessed
v.v. thinking about someone or something all the time. You use this when you cannot stop focusing on one specific thing.
v. preoccupied with a single person, idea, or object to a degree that is excessive or unhealthy.
She is completely obsessed with her new hobby.
He became so obsessed with winning the competition that he stopped seeing his friends and family.
The detective was famously obsessed with the cold case, spending his retirement years scouring old archives for a single overlooked detail.
Typically functions as a predicative adjective following a linking verb; almost always takes the preposition 'with'.
He is obsessed by video games.He is obsessed with video games.While 'by' is occasionally used in passive constructions, 'with' is the standard preposition for the adjective form.