So that's the base of our, this purple, this, I guess, mauve or purple color is the base of it. But then it's kind of popping out of our screen. What I've drawn here in blue, you could view this as kind of the top ridge of the figure. And if you were to take cross-sections of the figure, and that's what this yellow line is, if you were to take cross-sections of this figure that are vertical, that are, I should say, perpendicular to the x-axis, those cross-sections are going to be isosceles-right triangles. So this cross-section is going to look like this if you were to look at, if you were to flatten it out. So over here it's sitting, it's popping out of your page or out of your screen, but if you were to actually flatten it out, the cross-section would look like this. It's going to be an isosceles-right triangle where the hypotenuse of the isosceles-right triangle sits along the base.