💳 Animated Interactive Card with validation using Vanilla JS

Here's my Interactive Credit Card challenge and yes... it was challenging 😅

I started using absolute positioning for the cards and of course this ended up being a bad idea for a responsive website and (of course) flexbox and grid made everything to work and respond to smaller screens (lots of divs required).

I tried to incorporate as many validation and restrictions I could think in the form using JavaScript, and also added a Major Industry Identifier for major credit card networks. If you feel like it, I encourage you to play around to see it working and maybe to spot some unoticed bug? 😬

My question for this challenge Does anyone knows how to acchieve that rounded border with gradiend for input:focus?

Any suggestion of how I can improve my project will be appreciated! Thanks in advance 🌻