Can you figure out my* rule? Drag the vectors in the graph to the left (or change the numbers below it) and watch how the vector in the graph to the right changes.
*This webpage was designed in response to a tweet by @mpershan. So technically, this is Michael Pershan's rule (though it is a very popular rule; others could lay claim to it as well).
This page uses the Desmos API, MathQuill (both of which were new to me), and Tangle.js