Base Apparel coming soon page

Hi,

If you know of ways to improve on the following, I would be grateful:

• DOM manip: how to get the red alert icon and alert message to show for say 3seconds, then disappear, prompting the user to re-type a valid email address.
• Email validation: still not sure how to do this. Are additional php scripts are required? Or regex check with JS?
• The SVG background doesn't quite line up with the jpeg design, if you know how to align this, it would be interesting to know.
• The form field doesn't look great at <375px, maybe the button icon could break to a new line? Interested to see how others achieved a cleaner design. Thanks