Very casual and friendly. Zero behavioral questions. One short excel test on sumif/sumifs. I think they most of all want to hire well intentioned people who can contribute positively to the company culture. I was referred, spoke briefly to the hiring manager, then spoke to the recruiter through a phone screen, then had a formal video interview with the hiring manager, and lastly an in-person interview with the hiring manager's manager. Very friendly great people. It's very important to dress formal, the dress code is business formal daily.