Responsive Mobile First Landing Page using HTML5 and CSS3

yeah, besides displaying both hero background img, you did good.

Hey! The desktop layout it's pretty good. But in resolutions below 1284px, the image starts to overflow and becomes less and less visible. Then, around 1040, the image gets duplicated and fills all the width of the screen, looking streched.

You're displaying both the hero-desktop and hero-mobile images.

The only other detail, it's the button. It looks a liiiiitle bit bigger than the text field. In the prototype they're the same size.

Try to play with the property box-sizing: border-box, and try to manually set the height of both the input field, and the button.