Starts with 80 question mental math test in 8 minutes. Need around a 55 to move on. After this there is a pure fit interview with HR, basic questions about why optiver, why trading, etc. Then there was another online test, this time around 26 questions both multiple choice and short answer. All probability and logic questions. Needed around a 19 to pass. After this test I had a purely technical interview with a trader. A lot of mental math questions, a fermi question, and a card game question about expected value. I think usually there are two rounds of these trader phone interviews, but I was invited to the superday after just one round. Superday was long (5 hours), with 6 technical interviews, an HR interview, and a shadow with a trader. A lot of the interviews focused on online games, only one of the six interviews had any questions related to financial theory. Also, some of the interviews were more difficult than they should have been due to the lacking verbal and social skills of the interviewers... Also, the vibe of the office seemed a lot more stressful/less fun than the other chicago prop trading firms I have seen in person.