Mobile-first design means building websites or apps starting with the phone...

https://reidwxzz567.image-perth.org/how-do-i-design-mobile-text-that-works-in-bright-sunlight

Mobile-first design means building websites or apps starting with the phone experience. It’s all about fast loading times, easy-to-tap buttons, and simple menus that make getting things done quick and painless on a small screen