In the book The Greedy Triangle, a triangle is dissatisfied with his shape. The triangle complains to the shapeshifter, who changes him into a new polygon by adding another angle and another side. Soon the shape is not content being a quadrilateral, and returns to the shapeshifter to have another angle and side added. This continues until the shape has so many sides and angles that it rolls as easily as a circle. The book introduces the correct geometric terminology each time the triangle is changed into a new shape.