## Purpose

Canonical specification for responsive-device-agnostic-layout requirements synced from OpenSpec change deltas.

## Requirements

### Requirement: Core layout is device-agnostic and responsive
The system SHALL render key surfaces (header, hero, feed, modal, footer, policy modals, and floating controls) responsively across mobile, tablet, and desktop viewports while preserving readability.

#### Scenario: Mobile layout behavior
- **WHEN** a user opens the site on a mobile viewport
- **THEN** content remains readable without horizontal overflow
- **AND** interactive controls including icon-only copy/back-to-top and policy modals remain reachable and usable

#### Scenario: Desktop and tablet adaptation
- **WHEN** a user opens the site on tablet or desktop viewports
- **THEN** layout reflows according to breakpoint design rules
- **AND** no key content or controls are clipped

#### Scenario: Readability-focused typography and contrast updates
- **WHEN** content is rendered in core reading surfaces
- **THEN** typography and color choices improve baseline readability
- **AND** updates remain compatible with responsive behavior across breakpoints

#### Scenario: Sticky shrinking glass header
- **WHEN** user scrolls downward
- **THEN** header remains sticky with slight height reduction, subtle elevation, and glass blur effect
- **AND** controls remain readable and usable at all breakpoints

#### Scenario: Sticky footer does not overlap core reading zones
- **WHEN** footer is sticky
- **THEN** content remains readable and interactive controls are not obscured
- **AND** mobile/tablet/desktop layouts stay overflow-safe
