Important! What is a quick and easy way to style up an HTML form for smartphones? Look here.
20180714/DuckDuckGo css style form for smartphone screens
20180714/DuckDuckGo css style html form for smartphone screens
20180714/https://www.sanwebe.com/2014/08/css-html-forms-designs
20180714/https://stackoverflow.com/questions/25681278/how-to-make-a-html5-form-responsive
Important! Make sure you also set the viewport width to your device width for pages that are designed to render on mobiles.
20180714/DuckDuckGo css responsive chrome mobile 20180714/https://webmasters.stackexchange.com/questions/85522/mobile-google-chrome-not-resizing-responsive-website#85718 20180714/DuckDuckGo browser mobile device viewport meta 20180714/https://developer.mozilla.org/en-US/docs/Mozilla/Mobile/Viewport_meta_tag
But, the best point in hand. Want to do accurate testing on mobile devices from desktops and laptops? Make sure you use the same browser that will be running on the mobile device, and then put that into mobile device emulation mode.
Also, don’t forget. The terminology that pundits are coining today for CSS that works on smartphones (as well as tablets, desktops, and laptops)? Responsive design.