Function
The first lesson's runtime in whole minutes, or null when it has none
It repeats the action rather than adding a new one, so a visitor who has
scrolled past the questions and the levels still has one obvious next step.
The home passes the same StartCourseLink the hero carries, so both always
lead to the same place. The band inverts the page's surface in the light
theme and glows in the dark theme, so it separates from the ground in both.
The landing's closing band: the offer restated once more, and the hero's primary action repeated.