Curve-shortening flow

Curve-shortening flow is like when a leaf or a twig on a tree grows. When the twig or leaf on the tree gets bigger it bends because of its own weight. Curve-shortening flow is like that, but with shapes that start out as circles instead of twigs and leaves. When curve-shortening flow is used, it changes the shape of a circle into something different. The idea is that the shape gets shorter, but not wider or taller. It's like the shape is shrinking but it keeps the same size. This makes it look like the shape is becoming more and more round.