Jigsaw puzzle

Claim 1

A jigsaw puzzle, comprising: a plurality of separable solid pieces, adjacent pieces being joinable along undercut mating jigsaw surface pairs defined by respective different plural cutting lines, and each cutting line moving through a respective jigsaw locus so that said pieces when joined form a single solid; at least some of said mating jigsaw surface pairs each being defined by a cutting line moving along a jigsaw locus that is in a first plane; others of said mating jigsaw surface pairs each being defined by respective cutting lines moving along respective jigsaw loci contained in a common second plane angularly related to the first plane; one first pair of said others of said mating jigsaw surface pairs forming a first puzzle portion and a second puzzle portion that can only be assembled by relative movement in a direction perpendicular to said second plane; at least one second pair of said some of said mating jigsaw surface pairs extending entirely through said first puzzle portion and through only one surface of said first pair without extending into said second puzzle portion to form a first and a second one of said pieces that can only be assembled by relative movement in a direction perpendicular to said first plane; and said first and second jigsaw surface pairs being means for requiring said pieces only be assembled in order of assembling said first and second pieces before assembling said first and second puzzle portions.