Modern CSS Patterns

CSS has evolved dramatically. Features that once needed JavaScript are now native. Here's what I use daily.

Container Queries

Components that respond to their container, not just the viewport:

css.card-container {
  container-type: inline-size;
}

.card {
  display: grid;
  gap: 1rem;
}

@container (min-width: 400px) {
  .card {
    grid-template-columns: 150px 1fr;
  }
}

Game-changing for reusable components.

The :has() Selector

The parent selector we've always wanted:

css/* Card with image gets different layout */
.card:has(img) {
  grid-template-rows: 200px 1fr;
}

/* Label changes when input is focused */
.field:has(input:focus) label {
  color: var(--accent);
}

/* Hide empty sections */
section:not(:has(*)) {
  display: none;
}

CSS Variables for Theming

css:root {
  --bg: #ffffff;
  --text: #1a1a1a;
  --accent: #6366f1;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #09090b;
    --text: #fafafa;
  }
}

.button {
  background: var(--accent);
  color: white;
}

Theme switching without JavaScript.

Grid for Page Layout

css.page {
  display: grid;
  grid-template-columns: 1fr min(65ch, 100%) 1fr;
  min-height: 100vh;
}

.page > * {
  grid-column: 2;
}

/* Full-width breakout */
.page > .wide {
  grid-column: 1 / -1;
}

Logical Properties

Write CSS that works in any writing direction:

css.sidebar {
  margin-inline-start: 2rem;  /* not margin-left */
  padding-block: 1rem;        /* not padding-top/bottom */
  border-inline-end: 1px solid var(--border);
}

Aspect Ratio

No more padding hacks:

css.video {
  aspect-ratio: 16 / 9;
  width: 100%;
}

.avatar {
  aspect-ratio: 1;
  border-radius: 50%;
}

Modern CSS is powerful enough that I rarely reach for CSS-in-JS anymore. The platform caught up.