designing-layouts

# Layout Systems & Responsive Design

## Purpose

This skill provides comprehensive guidance for creating responsive layout systems using modern CSS techniques. It covers grid systems, flexbox patterns, container queries, spacing systems, and mobile-first design strategies to build flexible, accessible interfaces that adapt seamlessly across devices.

## When to Use

Invoke this skill when:
- Building responsive admin dashboards with sidebars and headers
- Creating grid-based layouts for content cards or galleries
- Implementing masonry or Pinterest-style layouts
- Designing split-pane interfaces with resizable panels
- Establishing responsive breakpoint systems
- Structuring application shells with navigation and content areas
- Building mobile-first responsive designs
- Creating flexible spacing and container systems

## Layout Patterns

### Grid Systems

For structured, two-dimensional layouts, use CSS Grid with design tokens.

**12-Column Grid:**
```css
.grid-container {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--grid-gap);
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--container-padding-x);
}

.col-span-6 { grid-column: span 6; }
.col-span-4 { grid-column: span 4; }
.col-span-3 { grid-column: span 3; }
```

**Auto-Fit Responsive Grid:**
```css
.auto-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(280px, 100%), 1fr));
  gap: var(--grid-gap);
}
```

For complex grid layouts and advanced patterns, see `references/layout-patterns.md`.

### Flexbox Patterns

For one-dimensional layouts and alignment control.

**Holy Grail Layout:**
```css
.holy-grail {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.holy-grail__body {
  flex: 1;
  display: flex;
}

.holy-grail__nav {
  width: var(--sidebar-width);
  flex-shrink: 0;
}

.holy-grail__main {
  flex: 1;
  min-width: 0; /* Prevent overflow */
}

.holy-grail__aside {
  width: var(--sidebar-width);
  flex-shrink: 0;