Most "responsive" sites are desktop layouts squeezed into media queries. Here's the build checklist we run at aimEncoders to ship genuinely mobile-first frontends.

1. Write base styles for mobile, enhance with min-width

Your unguarded CSS should be the phone layout. Every min-width media query is a progressive enhancement, never a repair. If you find yourself writing max-width overrides to fix the desktop design on phones, the cascade is backwards.

2. Use fluid type and spacing

clamp() for type scale, relative units for spacing, and container query units where components need independence from viewport. Hardcoded pixel values at desktop sizes are where mobile layouts go to die.

3. Responsive images are a build step, not an afterthought

srcset + sizes on every content image, modern formats (WebP/AVIF) with fallbacks, loading="lazy" below the fold, and explicit width/height (or aspect-ratio) to kill layout shift.…