rompecabezas

noun
  1. A puzzle, typically a jigsaw puzzle, that requires assembling pieces to form a complete picture or solve a problem. noun
    She spent the afternoon working on a 1000-piece rompecabezas.
    The rompecabezas was challenging, but it was satisfying to see the final image come together.
  2. A complex or difficult problem or situation that requires careful thought and effort to solve. noun
    The mystery novel presented a rompecabezas that kept readers guessing until the end.
    The engineer faced a rompecabezas when trying to design the new system.