The restaurant is trying to attract more customers, and the new menu is an important 'piece of the puzzle'. [=an important part of what is being done]
Ecologists no longer view different species as independent, but instead see them as pieces of the same 'jigsaw puzzle'.
His strange behavior is a 'puzzle' to his friends. [=his friends don't understand the reason for his strange behavior]
(..) Salvatore, my love. A whole summer with my family, far from you, my days here go on forever. l see your name everywhere in a book, a crossword puzzle... a newspaper. You're always before my eyes. Today, alas, l have bad news. ln October we move to Palermo, where l'll go to university. (..)1988 Cinema Paradiso