  The tangram and Sei Shonagon Chie no Ita are popular dissection puzzles
consisting of seven pieces. Each puzzle can be formed by identifying edges from
sixteen identical right isosceles triangles. It is known that the tangram can
form 13 convex polygons. We show that Sei Shonagon Chie no Ita can form 16
convex polygons, propose a new puzzle that can form 19, no 7 piece puzzle can
form 20, and 11 pieces are necessary and sufficient to form all 20 polygons
formable by 16 identical isosceles right triangles. Finally, we examine the
number of convex polygons formable by different quantities of these triangles.
