Mobile-first design means building apps and websites with phones in mind first....

https://quebeck-wiki.win/index.php/Why_Do_Mobile_Users_Miss_Buttons_Even_When_They_Are_on_the_Screen%3F

Mobile-first design means building apps and websites with phones in mind first. It’s all about fast loading times, easy-to-tap buttons, and straightforward menus you can use without zooming