1st interview was 30 minute phone call. It consisted of some basic resume questions and technical questions from a class of my choice. I chose thermodynamics. The technical questions were pretty difficult. The second round was a presentation to the CTO/Co-Founder and 2 engineers. The engineers and CTO seemed very uninterested and didn't interact with me at all - it was basically me just talking to a wall for 30 minutes. I was rejected the next day. Overall, the first interview was a positive experience and the second was very negative.