Changing the background color of buttons

Question

Why won't the background color of the buttons change even after clicking the button
https://sololearn.com/compiler-playground/Wtkous9Ff2Y4/?ref=app

Answer 1

DO NOT put the link in the tag section. The tag section is for indicating the relevant programming language.

Answer 2

id must be unique. you cannot have to elements with the id #hi.

Also, wherever you got the code from, the div with class="Div-2" are not closed properly