adjective

directing a great deal of attention, interest, or activity towards a particular aim.

Darren knows what he wants and he’s very focused

concentrated,concentrating,attentive,absorbed,engrossed,fascinated,enthralled,enrapt,rapt,earnest,intense,studious,fixed,steady,steadfast,occupied,preoccupied,wrapped up,alert,watchful,observant,determined,resolved,firm,committed,single-minded,inflexible,obsessive,obsessed,fanatical,fixated