Responsive newsletter signup with form validation

Hi,

I made this project for fun, the most difficult part was positioning modal window after submitting form. It was a nightmare, because when it was working on desktop it wasn't working on mobile and vice versa. I would like to get some code review, becase I think my CSS especially isn't very clean. I would like to improve it :D. Also I am not sure about the JS, precisely in throwError() and reset(), I feel like I could use the toggle() method and it would work, but it wasn't so I left it like this. I think like I overcomplicated all the positioning stuff. I would like to get some advice about this positioning if it was necessary or not :D.

Thanks for responses!