ELI5: Explain Like I'm 5

Circle inversion

Okay, so let's pretend that you're playing with a really cool toy called a circle. This circle is like a big, round button, and you can move it around and draw on it with your markers. When you draw on the circle, it makes a design that's shaped like a doughnut.

Now, sometimes you might want to turn your circle inside-out. That means that the doughnut part goes inside, and the space in the middle becomes the outside. To do this, you need to press your circle onto a magic mirror. When you do this, something funny happens - the doughnut part shrinks down and gets flipped upside-down, while the space in the middle stretches out and becomes bigger.

This is kind of like what happens when we do something called circle inversion. When we have a circle on a piece of paper, we can imagine that it's sitting on top of a magic mirror. When we do the circle inversion, we're basically shrinking and flipping the circle, just like we did with your toy circle.

The cool thing about circle inversion is that it can help us solve math problems. We can use it to turn really hard problems into easier ones. It's kind of like playing a math game where you get to flip and move the pieces around until you find the answer.