I assume that you, the reader, have some experience with HTML and HTML5 documents. One of the most important new features in HTML5 is the canvas element for drawing. I describe briefly the drawing of filled-in paths of the appropriate color and filled-in text. Next, I describe coordinate transformations, used in this project for the two parts of the logo itself and for scaling, changing the size, of the whole logo. Lastly, I describe the range input element. This produces the slider.
Canvas is a type of element introduced in HTML5. All canvas elements have a property (aka attribute) called the 2D context. Typically, a variable is set to this property after the document is loaded: