---
name: nexus-ui-engine
description: Design System & Component rules for Blazor
---
# UI Standards

- **Atomic Design:** 
  - Build reusable components in `NexusReader.UI.Shared/Components`.
  - `Atoms`: Base elements (`NexusButton`, `NexusIcon`, `NexusTypography`).
  - `Molecules`: Small groups (`AiAssistantBubble`, `KnowledgeCheck`).
  - `Organisms`: High-level sections (`KnowledgeGraph`, `ReaderCanvas`).

- **Styling & Isolation:** 
  - Mandatory use of scoped CSS (`.razor.css`).
  - No global CSS except for design tokens in `app.css`.
  - Use `::deep` only when absolutely necessary to style child components.

- **Design System (Nexus Neon):**
  - **Color Palette:**
    - Primary Accent: `--nexus-neon` (`#00ff99`) - Used for borders, highlights, and icons.
    - Dark Mode: `--nexus-bg` (`#0a0a0a`), `--nexus-card` (`#141414`).
    - Light Mode: `--nexus-bg` (`#f8f9fa`), `--nexus-card` (`#ffffff`).
  - **Typography:**
    - UI Elements: `Inter` (Sans-Serif) for controls, menus, and labels.
    - Reading Content: `Merriweather` (Serif) for books and articles to ensure high readability.
  - **Effects:**
    - Subtle neon glows (`box-shadow: 0 0 15px rgba(0, 255, 153, 0.3)`).
    - Glassmorphism for overlays and modals.

- **Adaptive Layouts:**
  - Support `.platform-mobile` and `.platform-desktop` context classes.
  - Handle safe-area insets (`--safe-area-inset-*`) for mobile devices.

- **Accessibility (A11y):**
  - Touch Targets: Min `44x44px` on mobile (enforced via CSS variables).
  - Contrast: Minimum ratio of 4.5:1.
  - Semantic HTML: Use appropriate tags (`<button>`, `<article>`, `<nav>`).

- **Interactive Flow:**
  - AI Assistant interactions must be non-blocking and smoothly transition using CSS animations.
  - Interactive elements must have clear `:hover`, `:active`, and `:focus` states.