Technical questions in different difficulties, along with personal questions about my past and my degree, had to tell about a project in my studies in hardware and VLSI , then they asked a further question about it, wanted to improve something in the implementation

I entered into a room with two engineers and after they asked me about myself they started with the professional questions. First I was asked to implement a circuit which calculate 20x+7. Each time they added new limitations and difficulty that i had to deal with and change my circuit according to them. After this question they asked me some logical questions/ riddles