agents/plugins/ui-design/skills/responsive-design/references/fluid-layouts.md

Fluid Layouts and Typography

Overview

Fluid design creates smooth scaling experiences by using relative units and mathematical functions instead of fixed breakpoints. This approach reduces the need for media queries and creates more natural-feeling interfaces.

Fluid Typography

The clamp() Function

/* clamp(minimum, preferred, maximum) */
.heading {
  /* Never smaller than 1.5rem, never larger than 3rem */
  /* Scales at 5vw between those values */
  font-size: clamp(1.5rem, 5vw, 3rem);
}

Calculating Fluid Values

The preferred value in clamp() typically combines a base size with a viewport-relative portion:

/* Formula: clamp(min, base + scale * vw, max) */

/* For text that scales from 16px (320px viewport) to 24px (1200px viewport): */
/* slope = (24 - 16) / (1200 - 320) = 8 / 880 = 0.00909 */
/* y-intercept = 16 - 0.00909 * 320 = 13.09px = 0.818rem */

.text {
  font-size: clamp(1rem, 0.818rem + 0.909vw, 1.5rem);
}

Type Scale Generator

// Generate a fluid type scale
function fluidType({
  minFontSize,
  maxFontSize,
  minViewport = 320,
  maxViewport = 1200,
}) {
  const minFontRem = minFontSize / 16;
  const maxFontRem = maxFontSize / 16;
  const minViewportRem = minViewport / 16;
  const maxViewportRem = maxViewport / 16;

  const slope = (maxFontRem - minFontRem) / (maxViewportRem - minViewportRem);
  const yAxisIntersection = minFontRem - slope * minViewportRem;

  return `clamp(${minFontRem}rem, ${yAxisIntersection.toFixed(4)}rem + ${(slope * 100).toFixed(4)}vw, ${maxFontRem}rem)`;
}

// Usage
const typeScale = {
  xs: fluidType({ minFontSize: 12, maxFontSize: 14 }),
  sm: fluidType({ minFontSize: 14, maxFontSize: 16 }),
  base: fluidType({ minFontSize: 16, maxFontSize: 18 }),
  lg: fluidType({ minFontSize: 18, maxFontSize: 20 }),
  xl: fluidType({ minFontSize: 20, maxFontSize: 24 }),
  '2xl': fluidType({ minFontSize: 24, maxFontSize: 32 }),
  '3xl': fluidType({ minFontSize: 30, maxFontSize: 48 }),
  '4xl': fluidType({ minFontSize: 36, maxFontSize: 60 }),
};

Complete Type Scale

:root {
  /* Base: 16-18px */
  --text-base: clamp(1rem, 0.9rem + 0.5vw, 1.125rem);

  /* Smaller sizes */
  --text-sm: clamp(0.875rem, 0.8rem + 0.375vw, 1rem);
  --text-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);

  /* Larger sizes */
  --text-lg: clamp(1.125rem, 1rem + 0.625vw, 1.25rem);
  --text-xl: clamp(1.25rem, 1.1rem + 0.75vw, 1.5rem);
  --text-2xl: clamp(1.5rem, 1.2rem + 1.5vw, 2rem);
  --text-3xl: clamp(1.875rem, 1.4rem + 2.375vw, 2.5rem);
  --text-4xl: clamp(2.25rem, 1.5rem + 3.75vw, 3.5rem);
  --text-5xl: clamp(3rem, 1.8rem + 6vw, 5rem);

  /* Line heights scale inversely */
  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.75;
}

/* Apply to elements */
body {
  font-size: var(--text-base);
  line-height: var(--leading-normal);
}

h1 { font-size: var(--text-4xl); line-height: var(--leading-tight); }
h2 { font-size: var(--text-3xl); line-height: var(--leading-tight); }
h3 { font-size: var(--text-2xl); line-height: var(--leading-tight); }
h4 { font-size: var(--text-xl); line-height: var(--leading-normal); }
h5 { font-size: var(--text-lg); line-height: var(--leading-normal); }
h6 { font-size: var(--text-base); line-height: var(--leading-normal); }

small { font-size: var(--text-sm); }

Fluid Spacing

Spacing Scale

:root {
  /* Spacing tokens that scale with viewport */
  --space-3xs: clamp(0.25rem, 0.2rem + 0.25vw, 0.375rem);
  --space-2xs: clamp(0.375rem, 0.3rem + 0.375vw, 0.5rem);
  --space-xs: clamp(0.5rem, 0.4rem + 0.5vw, 0.75rem);
  --space-sm: clamp(0.75rem, 0.6rem + 0.75vw, 1rem);
  --space-md: clamp(1rem, 0.8rem + 1vw, 1.5rem);
  --space-lg: clamp(1.5rem, 1.2rem + 1.5vw, 2rem);
  --space-xl: clamp(2rem, 1.5rem + 2.5vw, 3rem);
  --space-2xl: clamp(3rem, 2rem + 5vw, 5rem);
  --space-3xl: clamp(4rem, 2.5rem + 7.5vw, 8rem);

  /* One-up pairs (for asymmetric spacing) */
  --space-xs-sm: clamp(0.5rem, 0.3rem + 1vw, 1rem);
  --space-sm-md: clamp(0.75rem, 0.5rem + 1.25vw, 1.5rem);
  --space-md-lg: clamp(1rem, 0.6rem + 2vw, 2rem);
  --space-lg-xl: clamp(1.5rem, 1rem + 2.5vw, 3rem);
}

/* Usage examples */
.section {
  padding-block: var(--space-xl);
  padding-inline: var(--space-md);
}

.card {
  padding: var(--space-md);
  gap: var(--space-sm);
}

.stack > * + * {
  margin-top: var(--space-md);
}

Container Widths

:root {
  /* Fluid max-widths */
  --container-xs: min(100% - 2rem, 20rem);
  --container-sm: min(100% - 2rem, 30rem);
  --container-md: min(100% - 2rem, 45rem);
  --container-lg: min(100% - 2rem, 65rem);
  --container-xl: min(100% - 3rem, 80rem);
  --container-2xl: min(100% - 4rem, 96rem);
}

.container {
  width: var(--container-lg);
  margin-inline: auto;
}

.prose {
  max-width: var(--container-md);
}

.full-bleed {
  width: 100vw;
  margin-inline: calc(-50vw + 50%);
}

CSS Grid Fluid Layouts

Auto-fit Grid

/* Grid that fills available space */
.auto-grid {
  display: grid;
  grid-template-columns: repeat(
    auto-fit,
    minmax(min(100%, 250px), 1fr)
  );
  gap: var(--space-md);
}

/* With maximum columns */
.auto-grid-max-4 {
  display: grid;
  grid-template-columns: repeat(
    auto-fit,
    minmax(min(100%, max(200px, calc((100% - 3 * var(--space-md)) / 4))), 1fr)
  );
  gap: var(--space-md);
}

Responsive Grid Areas

.page-grid {
  display: grid;
  grid-template-columns:
    1fr
    min(var(--container-lg), 100%)
    1fr;
  grid-template-rows: auto 1fr auto;
}

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

.full-width {
  grid-column: 1 / -1;
}

/* Content with sidebar */
.content-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

@media (min-width: 768px) {
  .content-grid {
    grid-template-columns: 1fr min(300px, 30%);
  }
}

Fluid Aspect Ratios

/* Maintain aspect ratio fluidly */
.aspect-video {
  aspect-ratio: 16 / 9;
}

.aspect-square {
  aspect-ratio: 1;
}

/* Fluid aspect ratio that changes */
.hero-image {
  aspect-ratio: 1; /* Mobile: square */
}

@media (min-width: 640px) {
  .hero-image {
    aspect-ratio: 4 / 3;
  }
}

@media (min-width: 1024px) {
  .hero-image {
    aspect-ratio: 16 / 9;
  }
}

Flexbox Fluid Patterns

Flexible Sidebar

/* Sidebar that collapses when too narrow */
.with-sidebar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-lg);
}

.with-sidebar > :first-child {
  flex-basis: 300px;
  flex-grow: 1;
}

.with-sidebar > :last-child {
  flex-basis: 0;
  flex-grow: 999;
  min-width: 60%;
}

Cluster Layout

/* Items cluster and wrap naturally */
.cluster {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: flex-start;
  align-items: center;
}

/* Center-aligned cluster */
.cluster-center {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
  align-items: center;
}

/* Space-between cluster */
.cluster-spread {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: space-between;
  align-items: center;
}

Switcher Layout

/* Switches from horizontal to vertical based on container */
.switcher {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.switcher > * {
  /* Items go vertical when container is narrower than threshold */
  flex-grow: 1;
  flex-basis: calc((30rem - 100%) * 999);
}

/* Limit columns */
.switcher > :nth-last-child(n+4),
.switcher > :nth-last-child(n+4) ~ * {
  flex-basis: 100%;
}

Intrinsic Sizing

Content-Based Widths

/* Size based on content */
.fit-content {
  width: fit-content;
  max-width: 100%;
}

/* Minimum content size */
.min-content {
  width: min-content;
}

/* Maximum content size */
.max-content {
  width: max-content;
}

/* Practical examples */
.button {
  width: fit-content;
  min-width: 8rem; /* Prevent too-narrow buttons */
  padding-inline: var(--space-md);
}

.tag {
  width: fit-content;
  padding: var(--space-2xs) var(--space-xs);
}

.modal {
  width: min(90vw, 600px);
  max-height: min(90vh, 800px);
}

min() and max() Functions

/* Responsive sizing without media queries */
.container {
  /* 90% of viewport or 1200px, whichever is smaller */
  width: min(90%, 1200px);
  margin-inline: auto;
}

.hero-text {
  /* At least 2rem, at most 4rem */
  font-size: max(2rem, min(5vw, 4rem));
}

.sidebar {
  /* At least 200px, at most 25% of parent */
  width: max(200px, min(300px, 25%));
}

.card-grid {
  /* Each card at least 200px, fill available space */
  grid-template-columns: repeat(
    auto-fit,
    minmax(max(200px, 100%/4), 1fr)
  );
}

Viewport Units

Modern Viewport Units

/* Dynamic viewport height - accounts for mobile browser UI */
.full-height {
  min-height: 100dvh;
}

/* Small viewport - minimum size when UI is visible */
.hero {
  min-height: 100svh;
}

/* Large viewport - maximum size when UI is hidden */
.backdrop {
  height: 100lvh;
}

/* Viewport-relative positioning */
.fixed-nav {
  position: fixed;
  inset-inline: 0;
  top: 0;
  height: max(60px, 8vh);
}

/* Safe area insets for notched devices */
.safe-area {
  padding-top: env(safe-area-inset-top);
  padding-right: env(safe-area-inset-right);
  padding-bottom: env(safe-area-inset-bottom);
  padding-left: env(safe-area-inset-left);
}

Combining Viewport and Container Units

/* Responsive based on both viewport and container */
.component {
  container-type: inline-size;
}

.component-text {
  /* Uses viewport when small, container when in container */
  font-size: clamp(1rem, 2vw + 0.5rem, 1.5rem);
}

@container (min-width: 400px) {
  .component-text {
    font-size: clamp(1rem, 4cqi, 1.5rem);
  }
}

Utility Classes

/* Tailwind-style fluid utilities */
.text-fluid-sm { font-size: var(--text-sm); }
.text-fluid-base { font-size: var(--text-base); }
.text-fluid-lg { font-size: var(--text-lg); }
.text-fluid-xl { font-size: var(--text-xl); }
.text-fluid-2xl { font-size: var(--text-2xl); }
.text-fluid-3xl { font-size: var(--text-3xl); }
.text-fluid-4xl { font-size: var(--text-4xl); }

.p-fluid-sm { padding: var(--space-sm); }
.p-fluid-md { padding: var(--space-md); }
.p-fluid-lg { padding: var(--space-lg); }

.gap-fluid-sm { gap: var(--space-sm); }
.gap-fluid-md { gap: var(--space-md); }
.gap-fluid-lg { gap: var(--space-lg); }

Resources

• Utopia Fluid Type Calculator
• Modern Fluid Typography
• Every Layout
• CSS min(), max(), and clamp()