There were 3 rounds. 1 technical, 1 puzzle solving and 1 was a general, 'get to know your role'. The first round focussed on programming and basics of OOP (I wasn't asked to program anything). Having a background in hardware, the interviewer also threw in some questions from computer architecture, but they weren't too difficult. The second tested logic through puzzles. The interviewers were friendly and calm, even were ready to help with an answer if I was stuck up (didnt need that)