# Depth and Surface

Aurora Core uses an **optical depth model**:

## Depth tiers
- Depth 1 — recessed, 8px blur
- Depth 2 — standard, 20px blur
- Depth 3 — elevated/focused, 32px blur

## What depth means here
Depth is not “bigger shadow.”
Depth is:
- blur intensity
- edge luminance
- internal light
- perceptual separation

## Usage
- Depth 1: inner panels, input-like areas, background tab wells
- Depth 2: normal cards and standard containers
- Depth 3: hover state, overlays, floating nav, focused surfaces

## Prohibition
Do not rebuild hierarchy with drop shadows once the depth system is established.