Whitespace.  Thanks atom.io.
Additional whitespace.
Avoid the Sharpie TM and go for something more generic.
Defining imaginary functions that look like real functions adds to the confusion.  The example below is sufficient.
Missing bracket.
Use the actual order to reinforce the concept.
Minor typo.
Merge pull request #88 from bakercp/edits-intro-to-graphics

Edits and comments for intro-to-graphics.