/elevation-and-depth

name: elevation-and-depth
description: Shadows and layering that lift elements above the surface. Use when designing cards, dropdowns, modals, tooltips or any floating element.
metadata:
  priority: 6
  pathPatterns:
    - "**/*.css"
    - "**/*.scss"
    - "**/tokens/**"
    - "**/theme/**"
    - "tailwind.config.*"
    - "design-system/**"
    - "components/**"
  promptSignals:
    phrases:
      - "shadow"
      - "elevation"
      - "card"
      - "border radius"
      - "depth"
      - "floating"
      - "modal"
      - "dropdown"
retrieval:
  aliases:
    - elevation
    - box shadow
    - card design
    - depth hierarchy
    - border radius
    - floating elements
  intents:
    - make a card stand out
    - design elevation system
    - set up shadow tokens
    - make hierarchy feel physical
    - style a modal or dropdown
  examples:
    - make this card feel elevated
    - set up a shadow scale for the design system
    - what border radius should cards use

Elevation and Depth

Elevation uses shadow and layering to communicate that an element sits above the base surface — giving UI a sense of physical depth. Combined with border-radius, it creates the tactile quality that makes cards graspable, modals clearly floating, and dropdowns feel like they've appeared on top of content.

The Elevation Scale

Define a small set of elevation levels as tokens. Each level maps to a specific UI role.

| Level | Token | Shadow | Role | |---|---|---|---| | 0 | `--shadow-none` | none | Flat surface, inline elements | | 1 | `--shadow-xs` | `0 1px 2px rgba(0,0,0,0.06)` | Subtle card, table row hover | | 2 | `--shadow-sm` | `0 1px 3px rgba(0,0,0,0.10), 0 1px 2px rgba(0,0,0,0.06)` | Card, input focus ring area | | 3 | `--shadow-md` | `0 4px 6px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.06)` | Dropdown, popover | | 4 | `--shadow-lg` | `0 10px 15px rgba(0,0,0,0.08), 0 4px 6px rgba(0,0,0,0.05)` | Modal, dialog, side drawer | | 5 | `--shadow-xl` | `0 20px 25px rgba(0,0,0,0.08), 0 8px 10px rgba(0,0,0,0.04)` | Command palette, full-screen overlay |

Keep shadows subtle. Dark, heavy shadows feel dated and visually aggressive. Light, diffuse shadows feel modern and material.

The "Shadow + Border" Rule

A subtle shadow on a white surface can sometimes "wash out," making the edge of a card feel fuzzy or indistinct.

• **Rule:** For elevated white cards or sections, pair the shadow with a **1px border** that is slightly darker (1.5x to 2x) than the shadow's core tone (e.g., a medium grey like `#E2E8F0` or `grey-200`).
• **Effect:** The border defines the physical boundary of the card, while the shadow provides the depth. Together, they make the component "pop" with much higher clarity than using either alone.

Hover Needs a Defined Edge

A card that shifts **background colour on hover** must have a defined edge — a border, shadow, or clear radius boundary. Without one, the shift has no shape and reads as a stray fill, not a highlighted card. **On a borderless, flat card, a background-change hover is forbidden** — use a border or a shadow (elevation) on hover instead.

Subtle Gradients for Depth

Gradients can be used to bring "liveliness" to an interface and reinforce the sense of elevation.

• **The Lighting Metaphor:** A subtle linear gradient (top-to-bottom) that is slightly lighter at the top mimics natural overhead lighting. This makes a surface feel more physical and elevated than a flat fill.
• **The 5% Rule:** Keep the gradient extremely subtle. A change in lightness of only 2–5% between the top and bottom is usually enough. If the user can easily see where the gradient starts and ends, it is likely too heavy.
• **Usage:** Apply to primary buttons, hero cards, and header sections to improve visual hierarchy and brand personality.

Pairing Elevation with Border-Radius

Border-radius and shadow work together to define the character of a surface. The combination signals the element's role and the product's visual tone.

| Surface | Shadow | Border-Radius | Tone | |---|---|---|---| | Inline chip / tag | none | `--radius-full` (pill) | Flat, lightweight | | Card | `--shadow-sm` | `--radius-md` (8–12px) | Graspable, contained | | Dropdown / popover | `--shadow-md` | `--radius-md` (8px) | Floating, contextual | | Modal / dialog | `--shadow-lg` | `--radius-lg` (12–16px) | Prominent, focused | | Toast / notification | `--shadow-md` | `--radius-md` | Ephemeral, above content | | Button | none or `--shadow-xs` | **consistent across all buttons** — see below |

A Thick Accent Border and a Radius Never Share an Edge

Do not run a heavy coloured border along one side of a rounded box. Borders miter: where the accent meets its neighbours the renderer cuts a diagonal seam, and the radius bends that seam into a curve, so the accent visibly narrows and peels away before the corner ends. A 4px edge on an 8px radius spends most of its length tapering. Give the accent its own filled element instead, a bar or a wash that the container's radius clips cleanly, or keep the box square where the accent runs. A fill has no miter and no taper.

Border-Radius Consistency Rule

**Button border-radius must not vary within a product.** All buttons — primary, secondary, destructive, ghost — use the same radius token. Varying radius between button types breaks visual consistency and implies a semantic difference that does not exist.

/* Correct: one radius for all buttons */
.btn { border-radius: var(--radius-button); }

/* Wrong: different radii for different button variants */
.btn-primary { border-radius: 8px; }
.btn-secondary { border-radius: 4px; }  /* ← breaks consistency */

The button radius token is a brand decision — set it once, apply it everywhere.

Text Shadow for Contrast and Separation

`text-shadow` can lift text off a background without changing colours — useful when contrast is marginal or text sits on a photograph, gradient, or complex background.

The effect must be impe