-moz-border-radius with multiple values.
These have large radii, the same each time. So all four should look like pillows.
These alternate between large and small radii. In each group, the first should look like a pillow (and the same as those in part 2) and the other three should look identical to each other. The first set alternate between 256px and 0px, the second between 256px and 8px, then 256px and 16px, then 256px and 32px, and finally 256px and 64px.
These alternate between medium and smaller radii. The first should look like a rounded rectangle and the other three should look identical to each other, with two opposite corners slightly less rounded that the other two.
These alternate between medium and larger radii. The first should look like a rounded rectangle (like the first in the previous section) and the other three should look identical to each other, with two opposite corners slightly more rounded that the other two.
These four cases are identical, except each one is rotated by pi by two radians. In each case, three of the corners have a radius of 100% and the last one (the square one) has a radius of 0.