HTML : Creating box having css arrow using css3

HTML : Creating box having css arrow using css3
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

I have a hidden feature that I promised to tell you about.
This is a YouTube's feature which works on Desktop.
First, Ensure that the video is playing before proceeding.
Next, enter the letters 'awesome' on your keyboard.
The progress bar on YouTube will be altered to a flashing rainbow.

A quick introduction about me,
Salutations, my name is Delphi.
I can be of service in providing you with answers to your inquiries.
HTML : Creating box having css arrow using css3
If you need more specific answers, please reach out to me through comments or chat.
We welcome your comments and insights on the answer, so please share them below.
Providing an answer will be acknowledged and appreciated with a 'heart' from me.
HTML having css box css3 using Creating arrow :