Amazon Developer interview questions

I was first contacted by their HR in late October about the possible position in Amazon. I had two phone interviews with them. Both interviewers are friendly. They asked mostly CS and programming related questions as well as the OOD problem. I did well in the phone interviews. After a week, I was informed that they want me to go on-site for a formal interview. The onsite interview was tough, I've talked to seven interviewers. Each one for one hour. Most interviewers are friendly. Some questions are really tough and open. I know I still have so much to improve interms of my technical skill. After all, I am a fresh graduate trying land my first job. I didn't get the offer as I expected. But I feel I learned a lot.