Responsive Interactive Card Details Form using CSS Flexbox

Some suggestions:

Instead of using the keyup event, you can instead use the input event that is executed when the value of the input is changed in real time.

📖 Info: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/input_event

You could also show the default text on the cards when the inputs are empty (using the input event when they are empty).

You can validate the name input to avoid typing numbers or symbols

I hope it helped you 😄✌