<p>A plane jigsaw puzzle has multiple plastic pieces with concavo-convex structures on side edges, where the plastic puzzle pieces are matched and connected to concavo-convex structures. A chamfer angle is set at the edge between pieces, and the height of the chamfer angle to the edge interface of the two adjacent pieces is from 5% to 50%. The contact area of the two opposite adjacent pieces is 95% to 50% of the contact area of the corresponding edges.</p>
