/* Base styles for mobile */
.container {
  padding: 1rem;
}

/* Tablet and up */
@media (min-width: 768px) {
  .container {
    padding: 2rem;
  }
}

/* Desktop and up */
@media (min-width: 1024px) {
  .container {
    max-width: 1200px;
    margin: 0 auto;
  }
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1rem;
}

h1 {
  font-size: clamp(1.5rem, 4vw + 1rem, 3rem);
}

<img
  src="image-800.jpg"
  srcset="image-400.jpg 400w, image-800.jpg 800w, image-1200.jpg 1200w"
  sizes="(max-width: 600px) 100vw, (max-width: 1000px) 50vw, 800px"
  alt="Description"
>

/* Small phones */
@media (min-width: 320px) { }

/* Large phones */
@media (min-width: 480px) { }

/* Tablets */
@media (min-width: 768px) { }

/* Laptops/Desktops */
@media (min-width: 1024px) { }

/* Large screens */
@media (min-width: 1280px) { }

/* Extra large screens */
@media (min-width: 1536px) { }

<meta name="viewport" content="width=device-width, initial-scale=1">