3 separate interviews with increasing intensity. Overall, pretty standard

I was referred through a friend for an open position. I was contacted by the recruiter for an initial phone screen. A couple weeks later, an engineer contacted me and grilled me on technical application questions over the phone. Upon passing I was scheduled to do a group interview and presentation on the application. The group interview started with a few greetings and then I began a 30 minute presentation with questions at the end. Questions were made between my presentation and resume. Mostly the questions were made to see how I fielded tough and unanswerable questions.