add frontend skills

skills/frontend-design/reference/spatial-design.md

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+# Spatial Design
+
+## Spacing Systems
+
+### Use 4pt Base, Not 8pt
+
+8pt systems are too coarse—you'll frequently need 12px (between 8 and 16). Use 4pt for granularity: 4, 8, 12, 16, 24, 32, 48, 64, 96px.
+
+### Name Tokens Semantically
+
+Name by relationship (`--space-sm`, `--space-lg`), not value (`--spacing-8`). Use `gap` instead of margins for sibling spacing—it eliminates margin collapse and cleanup hacks.
+
+## Grid Systems
+
+### The Self-Adjusting Grid
+
+Use `repeat(auto-fit, minmax(280px, 1fr))` for responsive grids without breakpoints. Columns are at least 280px, as many as fit per row, leftovers stretch. For complex layouts, use named grid areas (`grid-template-areas`) and redefine them at breakpoints.
+
+## Visual Hierarchy
+
+### The Squint Test
+
+Blur your eyes (or screenshot and blur). Can you still identify:
+- The most important element?
+- The second most important?
+- Clear groupings?
+
+If everything looks the same weight blurred, you have a hierarchy problem.
+
+### Hierarchy Through Multiple Dimensions
+
+Don't rely on size alone. Combine:
+
+| Tool | Strong Hierarchy | Weak Hierarchy |
+|------|------------------|----------------|
+| **Size** | 3:1 ratio or more | <2:1 ratio |
+| **Weight** | Bold vs Regular | Medium vs Regular |
+| **Color** | High contrast | Similar tones |
+| **Position** | Top/left (primary) | Bottom/right |
+| **Space** | Surrounded by white space | Crowded |
+
+**The best hierarchy uses 2-3 dimensions at once**: A heading that's larger, bolder, AND has more space above it.
+
+### Cards Are Not Required
+
+Cards are overused. Spacing and alignment create visual grouping naturally. Use cards only when content is truly distinct and actionable, items need visual comparison in a grid, or content needs clear interaction boundaries. **Never nest cards inside cards**—use spacing, typography, and subtle dividers for hierarchy within a card.
+
+## Container Queries
+
+Viewport queries are for page layouts. **Container queries are for components**:
+
+```css
+.card-container {
+  container-type: inline-size;
+}
+
+.card {
+  display: grid;
+  gap: var(--space-md);
+}
+
+/* Card layout changes based on its container, not viewport */
+@container (min-width: 400px) {
+  .card {
+    grid-template-columns: 120px 1fr;
+  }
+}
+```
+
+**Why this matters**: A card in a narrow sidebar stays compact, while the same card in a main content area expands—automatically, without viewport hacks.
+
+## Optical Adjustments
+
+Text at `margin-left: 0` looks indented due to letterform whitespace—use negative margin (`-0.05em`) to optically align. Geometrically centered icons often look off-center; play icons need to shift right, arrows shift toward their direction.
+
+### Touch Targets vs Visual Size
+
+Buttons can look small but need large touch targets (44px minimum). Use padding or pseudo-elements:
+
+```css
+.icon-button {
+  width: 24px;  /* Visual size */
+  height: 24px;
+  position: relative;
+}
+
+.icon-button::before {
+  content: '';
+  position: absolute;
+  inset: -10px;  /* Expand tap target to 44px */
+}
+```
+
+## Depth & Elevation
+
+Create semantic z-index scales (dropdown → sticky → modal-backdrop → modal → toast → tooltip) instead of arbitrary numbers. For shadows, create a consistent elevation scale (sm → md → lg → xl). **Key insight**: Shadows should be subtle—if you can clearly see it, it's probably too strong.
+
+---
+
+**Avoid**: Arbitrary spacing values outside your scale. Making all spacing equal (variety creates hierarchy). Creating hierarchy through size alone - combine size, weight, color, and space.