First a phone screen with a recruiter, then two one on ones, then a half-day and presentation. As others have said, the design challenge is a bit odd in that it's independent - definitely not a whiteboard challenge - and that there seems to much more emphasis on a polished final product/presentation vs seeing how you think, work and collaborate. Maybe that's what's most useful for them in determining who is going to be successful there, but it was definitely way more unpleasant and stressful than a typical technical interview.
In general, everyone seemed really nice and my one-on-ones just felt like relaxed discussions. Culture-wise, it does feel like more of a consultancy and business-casual vibe than a startup/creative/design-led vibe, but that's just an assumption from a couple of remote calls (and not necessarily a bad thing - if you're in consulting you're probably used to/expecting that), but wasn't really the right fit for me. I was also kind of disappointed they just sent an automated rejection email after all that time and conversation.