Responsive card and checkout pop-up with VANILLA JAVASCRIPT/CSS

Hi, guys!

This is my solution to this challenge. But if you take the closest look, you'll see that it is a bit different from the one proposed.

Since I am learning Javascript I used this challenge to practice it. I know that are some challenges here that have Javascript, but using this one wasn't in my plans when I started doing it. It turns out to be something bigger than what I expected, and I still have some ideas to implement, but since I can not see the final version of it yet I decided to publish it already before it differs a lot from the website challenge. But I will keep using this template to practice some Javascript.

I know that the CSS file is too big, because of it, I will use SASS instead so it will be easier to maintain.

This is what I implemented:

• Change between dark and light mode
• Interact with the 'Change' button on the card to select the type of the plan (Annual Plan or Monthly Plan) and therefore see its price -Click on the 'Proceed to Payment' button and go to a checkout pop-up where the user could enter their details and change the Billing Cycle -Go back to the card by the 'Back' button

The dark mode was inspired by some solutions from @correlucas who makes very creatives ones

All feedback is appreciated!