Apptentive Software Developer interview questions

They give an online AP design and implementation (UFO) exercise. If you are reading this review, you might get same exercise. After that they call me for the onsite interview. They are very unprofessional. Even they (onsite interviewer) did not review my code properly. I finished the answer correctly and implemented my solution within 15 minutes. They told me the answer is correct . And when the give me feedback for the interview , the HR told me, "I am very strong in system design, but i did not discuss well". what ????. Also for coding interview I did right and implemented very quickly (within 15 minutes) . The HR said I was not collaborative in the coding interview. They are so unprofessional. Do not go there. The bad interview experience I ever had and so frustrating . And the interviewer were pretty un-experienced. One of them was joined 1 month ago and other one just 8 month ago.