Heels not only have to be the right height but in the right position: not too far back, but under the centre of the heel so they support your weight properly, following the natural line of your body.

When it became clear that the wealth being created on paper was out of line with the real value of the homes themselves, the pyramid fell under its own weight.

The next line says if the weight of i is greater than a w, well then I know I can't put it in.