Arm Graduate Engineer Systems IP interview questions

I applied for the job through the Arm Careers page by submitting my CV and Covering Letter around Novemeber time. About 1-2 weeks later, I received an invite to a video interview which had to be completed within 3 days. The video interview was very straightforward with questions like "rate yourself out of 10 for..." and a surprise simple coding question. I found the video interview to be a lot less stressful and easier than a telephone interview. After another week or so, I was invited to a Face-to-Face interview in January which was originally scheduled when I had an exam. When I contacted them to rearrange the interview, they were very understanding and changed the interview to a more convenient time for me. On arrival at the office, I was greeted by the receptionist and asked if I wanted anything to drink which I thought was a really kind gesture. The two people who interviewed me were also very warming and didn't make me feel like I was imposing. Firstly, I was asked about my project I was working on for University. They then quickly started the technical questions which involved deriving the functions of a complex CMOS circuit. I was then asked to draw a half adder on the whiteboard using logic gates and then describe the circuit using a HDL (I used VHDL). Further questions about the adder were asked which included latching the outputs and how you would appropriately test the outputs. I was then given a piece of paper which explained a scheduling problem and was asked to derive pseudocode for an implementation. Finally, I was asked about OOP and what it is used for. Throughout the entire interview, the interviewers were really nice and made me feel comfortable. Once the interview was over, the receptionist reimbursed the travel expenses to get there. The only criticism I have is when I asked at the end of the interview “whether there was anything that they were concerned about me as a candidate”, the interviewer politely declined. A few days later, after the interview, I was sent an offer rejection email but with no explanation on why I was rejected which left a bitter feeling for the whole application process especially since I asked.