HTML and CSS solution using flexbox

Replace <div class="container"> with the main tag to fix the accessibility issues. click here for more on web-accessibility and semantic html

To center .qr on the page using flexbox, replace the height in the body with min-height: 100vh. Give h1 and p the same font-size of 15px which is 0.9375rem.

Replace the height in .card with a padding value for all the sides, this will prevent the content from overflowing on smaller screens and its a responsive replacement. padding:16px

For a responsive content, replace the width .qr with `max-width and give the img a max-width of 100% instead of a width.

Use relative units like rem or em as unit for the padding, margin, width values and preferably rem for the font-size values, instead of using px which is an absolute unit. For more on CSS units Click here

Hope am helpful.

Well done for completing this challenge. HAPPY CODING

Good job AntoineReibel but you need to take responsive design in consider I tested your component on Samsung Galaxy S8+, and the design is not true my suggestion is to build for mobile first then use min-width: 768px for desktop