• this-classList-toggle can be used to toggle between class to remove & add it.
• Learned about transition in CSS which used to give smooth transtion of property in given specified time.
• element > * means that the child of elements & * means to apply to all
• :root means it selects the document's root element
• There is box-shadow & text-shadow available in CSS.

• We are mainly using Flexbox, which are 3 means inside that inside that.
• We have to do transition first increasing the box size & then show the text.
• We make specific classes for open & active & toggle them when the user clicks on it.

This was pretty tough for me as it the nesting of flexbox & transition effect that I don't know much.