For the phone interview, the interviewer called me unexpectedly because the recruiter forgot to tell me the schedule. The design exercise is to design something for their existing Skillz platform. You get to present this to their team during the first session of your onsite interview If you fail to impress them, that's the end of your first onsite interview. If things go well, they will invite you for the second onsite, which they didn't tell me until I went there for the first one. After I had my second onsite, they stopped responding when I followed up. An interesting thing is only two weeks later, the same recruiter reached out on LinkedIn to see if I was interested in the same position at their company.