This design is known as a "dish piston," characterized by its concave shape, and is used primarily in high-compression ...

You can get pyramids with different shaped bases. Triangles, pentagons, hexagons, any shape. And a circle becomes a sphere with just one large, curved face, like a ball. Perfect for, uh ...

Have a look at these three shapes. One of them is not a polygon. Can you work out which? A circle is not a polygon because it doesn’t have straight sides. Polygons can look quite different ...