Responsive layout with CountUp.js, html and css

This one was interesting! some surprises found while dealing with dates and how to properly validate the corner cases (February with 28 days, or 30/31 days)

I've used a mobile first approach with vanilla JS and CSS, the data validation is done with JS and the error feedback has been introduced using the :invalid and ::before / ::after pseudoelements.

The count up is animated using a lightweight library, https://inorganik.github.io/countUp.js/

Quite happy with the result, feedback is more than welcome!