Directions on the page are no longer explicit enough.
Codepen has revised the CSS inclusion list of versions so that saying one should apply “Bootstrap” is no longer explicit, since it includes versions 3 and 4.
Source page URL:
Get Set for our Front End Development Projects
Source page text description:
Click the gear in the upper left hand corner of the CSS box, then scroll down to “Quick add” and choose Bootstrap. Now give your h1 element the class of text-primary to change its color and prove that Bootstrap is now available.
Codepen quick add option image:
#codepen::tag #bootstrap3::tag #bootstrap4::tag