A Primer on Bezier Curves: finding y, given x

A small but important update to the Primer: after seven years there is now finally a section that explains how you can find a y coordinate, given an x coordinate, for functions that "look like they should just be normal functions".

As parametric curves, Bezier curves are notorious for being loopy (heck, it's _the_ reasons we use them in all manner of graphic design) but there's plenty of cases where they're not: CSS transitions, audio EQ, image leveling, etc. can all use Bezier curves as their control function, but that frickin control variable means you can't just get y, if you know x.

This new section explains exactly how to get around that. I should have written it years ago =)