Activision Blizzard interview questions

Received an email for a phone interview. I had a phone interview with VPHR after one week or so.

The interview consisted of 3 phone interviews: an initial one with HR, one with a manager, followed by another one with the director. The last two interviews were technical, with questions about my projects, linear algebra, my favorite/commonly used software packages. A question about my favorite math course, and why? The final interviewer asked if I would like to have an on-site interview, I said yes, and then I never heard from them again.