Beyond elementary school, kids are more apt to enjoy challenging puzzles that appeal not only to younger members of the family but adults as well. The Ravensburger Krypt Silver 654 Piece Blank Jigsaw Puzzle is one of the most unique and challenging jigsaw puzzles available. The entire puzzle is a single color and the pieces are shiny metallic. Rather than creating a picture, this puzzle is about identifying the types of pieces and how they fit together. The puzzle set includes a puzzle map.