Phone interview with one of their front end engineers who explained more about the company and then asked one sorting algorithm question and one vertical center css question, both via HackerRank/CodePair.

Applied through a referral from a friend. Started with a recruiter screen, then went to a 1 hour technical interview over the phone, and ended with an all day interview onsite. Overall the interview was very practical and mostly involved building things in Javascript, HTML, and CSS. There were more CSS questions than I expected, so make sure you're comfortable positioning items and building layouts under time constraints and while being watched by an interviewer.