Extremely casual. Lots of joking, lots of laughter. The questions were mostly to get to know personality rather than technical knowledge. After being hired, realized the way the job was explained in the interview wasn't super similar to the actual day to day of the job I ended up taking. Phone interview first- phone interview was honestly two questions about when I could start if I applied and if I wanted to work at Brooks. In person the week after with two hiring managers. Offer came in about a week after offer.