CodyHouse publishes free HTML, CSS, and JavaScript components and tutorials for front-end developers.
Commenters recommend it as a useful source of modern web effects, and link its post on CSS custom properties versus Sass variables.
I recently came across this, you might find the approach interesting (even if not using the CodyHouse framework as such):
https://codyhouse.co/blog/post/css-custom-properties-vs-sass-variables
similar effects:
https://codyhouse.co/demo/reading-progress-indicator/index.html
http://tympanus.net/Development/StorytellingMap/
https://tympanus.net/codrops/ and https://codyhouse.co/ are very useful for modern web effects stuff.
https://codyhouse.co/library