Responsive Design: Mobile First vs. Desktop First

When I built my first responsive site, I designed it for my 24-inch monitor and then tried to 'shrink it down' for phones. It was a disaster of overlapping elements and tiny text. The industry standard now is 'Mobile First'. This approach means you start by writing CSS for the smallest screen size (mobile) and then use min-width media queries to add styles for larger screens. It’s mentally easier to add complexity than to strip it away. For example, you set your default styles for a single column layout on mobile. Then, at a breakpoint of 768px, you use flexbox or grid to transform that layout into multiple columns. This also improves performance because mobile devices aren't loading large desktop styles. Tools like Chrome DevTools' device toolbar are invaluable for testing. Remember to always set the viewport meta tag in your HTML: <meta name='viewport' content='width=device-width, initial-scale=1.0'>.