css

 1. membuat line tree nested

https://codepen.io/bisserof/pen/nrMveb

https://www.google.com/amp/s/onaircode.com/html-css-tree-view-examples/amp/

2. responsive background 

https://stackoverflow.com/questions/485827/css-100-height-with-padding-margin

3. kumpulan animas css

https://medium.com/@skhans/20-css-tools-for-awesome-animations-in-your-designs-6828b8d8a568