1: Design challenge that was supposed to take 30 minutes, 4 different configurations of a system. Presumably impressive enough to continue wasting my time. 2: Phone screen with COO that went well. Another 30 minutes. 3: Video call, which the interviewer was 15 minutes late to, in which I was asked a few generic mechanical engineering questions and how I would approach some common day to day issues. This interviewer gave good feedback. Another 45 minutes. 4: Another design challenge, this time open ended in length. Essentially a homework set this time. 1 design problem, a camera holder with very specific specifications. 1 technical problem. The technical problem took a bit to complete, never received any feedback on this. The design problem wasn't too hard to meet their specifications. Received feedback saying it didn't pass their test. Provided 4 more specifications (that were not stated prior) and asked me to resubmit. Provided a second embodiment of their concept. Only piece of feedback I received was it met all requirements however did so in a way that wasn't useful for them. Complete waste of time, really terrible communication from the CTO. I should have stopped responding at the 2nd design challenge. They had all the information they needed to make a decision based on my qualifications at that point regarding an in person interview. Definitely dodged a bullet working for the CTO, so all in all would not recommend.