Majority of my story takes place in a prison. The only time it takes place outside of it shortly beginning and end of it. One complaint I got was it lacked world building. The most I can do is take outside influences, culture, customs and infuse it in the prison. Basically, the world is the prison. The book is sci-fi, but the MC doesn't get to experience the glamourous sci-fi world but only in the prison. What do you folks suggest?