Responsive web design with flexbox and media queries

I'm afraid you need to rewrite quite a bit of this, especially the CSS. The scale property has made this inaccessible and non-responsive. It is unreadable. You don't need to do any of this complicated stuff you've added. It's really important to build robust solutions that everyone can access. Don't try to micromanage the code.

• In HTML all content should be contained within landmarks. This is a single component demo but it's good practice to still wrap it in a main landmark so you build the habit and don't miss it out later.
• The image on here is the most important content on the page. That means it must have an alternative description that is accurate. This needs to say what the image is (QR code) and where it goes (to FrontendMentor.io).
• as this is a single card that would never serve the main title of the webpage that tells you it should not have an h1. Choose a level with a lower importance like H2.
• get into the habit of always including a full modern CSS reset at the start of the styles in every project you do. Andy Bell or Josh Comaeu both have good ones you can look up and use.
• the body doesn't need width 100vw. As soon as you add that anywhere all that can do is cause overflow problems. Because viewport units don't account for Device notches or the width of scrollbars, meaning 100vw actually equates to the full width of the screen plus the width of the scroll bar when it's present.
• the body also doesn't need overflow scroll. Let it overflow be automatic.
• to centre a component on the page use flex column properties. That wrapping element such as body main can have a small amount of padding in pixels so that the content never hits screen edges.
• don't style on IDs. That's not what they're for. IDs have very important purposes in html. Keep CSS specificity low by using Single class selectors as much as possible.
• the image doesn't need most styles you've added. All it needs is border radius and the standard styles that would be part of a CSS reset anyway Display block and Max width 100%.
• components max width should be in rem and not pixels. This allows the layout to scale correctly for all users including those who have a different text size setting in their browser or device.
• the component should have some padding on all sides.
• main shouldn't have background colour or a shadow.
• remove the huge padding from main.
• remove all scale properties.
• remove all media queries.
• remove all position relatives and directional properties.
• make sure you understand the difference between padding and margin. The usage here is unusual. I've written a post about this if you want to read more: https://fedmentor.dev/posts/padding-margin/

I hope this is helpful. Take your time and refactor this fully, all of these changes are pretty much essential. The key learning points are to focus on keeping everything simple, think through the HTML elements carefully, use a CSS reset at the start, and only add the minimal styles that you need.

I like the way you used the media query and the scaling.