Here is a very simple application of GeoGebra that I created this morning in about half an hour.
Simply created, yet totally impossible when I was a student, and largely impossible and generally improbable when I was a teacher. It depends on the correct technology and a teacher who can make it or at least use it.
Little technological things like this have the potential for creating those "aha!" moments, the presence of which are mileposts in the life of the mathematician, the absence of which create the dead ends of the math phobic.
We need to go out of our way to enable these "aha!" moments.
Improving the mathematical skills and knowledge of our country requires it.
If you wish to download the file itself and make your own modifications, you can get it here.