# FalahOS Design & App Building Guide

> **Purpose:** This document defines the FalahOS design system, UI/UX principles, and Svelte 5 implementation patterns. AI agents building or extending FalahOS apps MUST read and follow this guide. Every design decision in this guide exists for a reason — deviations should be the exception, not the habit.

---

## Table of Contents

1. [Design Philosophy](#1-design-philosophy)
2. [Visual Identity](#2-visual-identity)
3. [Component Architecture](#3-component-architecture)
4. [UX Patterns](#4-ux-patterns)
5. [Svelte 5 Implementation](#5-svelte-5-implementation)
6. [PWA Configuration](#6-pwa-configuration)
7. [Animation & Motion](#7-animation--motion)
8. [Data & State Management](#8-data--state-management)
9. [Responsive Design](#9-responsive-design)
10. [Accessibility](#10-accessibility)
11. [Performance Budget](#11-performance-budget)
12. [Project Structure](#12-project-structure)
13. [AI Agent Workflow](#13-ai-agent-workflow)
14. [Checklist: New Feature](#14-checklist-new-feature)

---

## 1. Design Philosophy

### Core Principles

| Principle | Meaning |
|-----------|---------|
| **Sovereign by default** | No third-party dependencies for core UX. No tracking, no analytics, no external fonts where avoidable. The app works without a server. |
| **Privacy by design** | Zero data collection. All processing is on-device. No accounts. No cookies. |
| **Premium minimalism** | High visual polish with minimal UI chrome. Every pixel earns its place. Dark theme is not a fallback — it's the canvas. |
| **Islamic essence, modern execution** | The spiritual context informs every design choice without resorting to clichés. Gold and green are not decorations — they carry meaning. |
| **Offline-first** | The app must be useful without internet. Core features (Qibla, Tasbih, Quran cache, Hijri) work fully offline after initial load. |

### Design Tenets

1. **Dark canvas, warm accents** — The background is always dark (#070A0D). Light is used sparingly as accent, never as background.
2. **Typographic hierarchy** — Three voices: Cinzel (display/serif — authority), DM Sans (body — readability), JetBrains Mono (data/meta — precision).
3. **Geometric intentionality** — The golden ratio, polygons, and clip-paths aren't decorative gimmicks. They echo Islamic geometric tradition in a modern way.
4. **Motion with purpose** — Transitions are brief (150-300ms). They communicate state change, not entertain. No idle animations.
5. **Content over chrome** — Navigation is compact (tabs, not hamburger menus). Cards have thin borders, not heavy shadows. Information density is high for the feature, low for chrome.

---

## 2. Visual Identity

### 2.1 Color System

```css
:root {
  /* Backgrounds — deep navy-black */
  --bg:           #070A0D;   /* Page background */
  --surface:      #0D1117;   /* Card/section surface */
  --card:         #111820;   /* Elevated cards, overlays */
  --border:       #1E2A36;   /* Subtle borders */

  /* Text */
  --text:         #E8E6E1;   /* Primary body text */
  --text-dim:     #8B8B8B;   /* Secondary/meta text */
  --text-muted:   #5A5A5A;   /* Footer/legal text */

  /* Accents */
  --gold:         #C9A84C;   /* Primary accent — faith, value, premium */
  --gold-light:   #D4B95A;   /* Gold hover/gradient variant */
  --gold-dim:     rgba(201, 168, 76, 0.15);  /* Gold background tint */

  --emerald:      #2ECC71;   /* Secondary accent — growth, success, nature */
  --green-dim:    rgba(46, 204, 113, 0.12);  /* Emerald background tint */

  /* Functional */
  --error:        #E74C3C;   /* Errors, destructive actions */
  --warning:      #F39C12;   /* Warnings */
  --info:         #3498DB;   /* Information */
}
```

**Usage rules:**
- Gold is for UI that carries spiritual/faith significance: active tabs, prayer times, headings, CTAs
- Emerald is for positive states, success indicators, confirmed data
- Never use white (#FFFFFF) — use `--text` (#E8E6E1) as the lightest color
- Never use pure black (#000000) — use `--bg` (#070A0D)
- Borders are always `--border`, never a lighter shade
- Text on gold backgrounds uses `--bg` (inverted for contrast)

### 2.2 Typography

**Voice assignments:**

| Font | Role | Weight | Size Scale |
|------|------|--------|------------|
| **Cinzel** (Google Fonts, serif) | Display headings, brand name, primary CTAs | 700-900 | 1.0-2.0rem |
| **DM Sans** (Google Fonts, sans-serif) | Body text, labels, paragraph content | 300-700 | 0.75-1.1rem |
| **JetBrains Mono** (Google Fonts, monospace) | Tab labels, meta text, footer, data values | 400-500 | 0.55-0.75rem |

**Implementation:**
```css
/* app.html */
<link href="https://fonts.googleapis.com/css2?family=Cinzel:wght@700;900&family=DM+Sans:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet" />

/* CSS variables */
--font-display: 'Cinzel', serif;
--font-body: 'DM Sans', sans-serif;
--font-mono: 'JetBrains Mono', monospace;
```

**Type scale:**
```
1.8rem — Brand name (Cinzel 900)
1.3rem — Tab icons (emoji/unicode)
1.0rem — Card headings (Cinzel 700)
0.85rem — Body text (DM Sans 400)
0.72rem — Button labels, data (JetBrains Mono 500)
0.62rem — Tab text, footer (JetBrains Mono 400, 0.25em letter-spacing)
```

### 2.3 Spacing System

Use a 4px baseline grid. Common values:

```css
--space-xs: 4px;
--space-sm: 8px;
--space-md: 12px;
--space-lg: 16px;
--space-xl: 20px;
--space-2xl: 24px;
```

- Card padding: 20px (`--space-xl`)
- Section gaps: 12px (`--space-md`)
- Tab padding: 8px 10px (`--space-sm` variable)
- Content max-width: 480px (mobile-first)

### 2.4 Surfaces & Depth

```css
/* Card */
.card {
  background: var(--surface);      /* or var(--card) for elevated cards */
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px;
  box-shadow:
    0 4px 20px rgba(0, 0, 0, 0.3),
    inset 0 1px 0 rgba(201, 168, 76, 0.05);
}

/* Header / Nav bar — glassmorphism */
header, .tab-nav, .footer {
  background: rgba(12, 17, 23, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  border-radius: 0 0 24px 24px;
}
```

### 2.5 Background Effects

**Noise texture** — applied via SVG filter on the `<body>` pseudoelement:

```css
body::before {
  content: '';
  position: fixed; inset: 0; z-index: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' ... %3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)' opacity='0.04'/%3E%3C/svg%3E");
  pointer-events: none;
  opacity: 0.4;
}
```

**Geometric light** — subtle radial gradients for depth:

```css
body::after {
  content: '';
  position: fixed; inset: 0; z-index: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% -10%, rgba(201,168,76,0.06) 0%, transparent 60%),
    radial-gradient(ellipse 40% 40% at 90% 80%, rgba(46,204,113,0.04) 0%, transparent 50%),
    radial-gradient(ellipse 60% 40% at -10% 50%, rgba(201,168,76,0.03) 0%, transparent 50%);
  pointer-events: none;
}
```

---

## 3. Component Architecture

### 3.1 Component Categories

| Category | Convention | Examples |
|----------|------------|----------|
| **Layout** | `src/lib/layout/` | `Header.svelte`, `TabNav.svelte`, `Footer.svelte` |
| **Feature** | `src/lib/*.svelte` (flat) | `PrayerTimes.svelte`, `Qibla.svelte`, `Quran.svelte` |
| **UI Primitives** | Inline in feature or global styles | Card, button (via `:global()`) |
| **State/Data** | Local to component via `$state` runes | No global stores unless truly shared |

### 3.2 Component Structure (Svelte 5)

```svelte
<script>
  // 1. $state declarations
  let data = $state(null);
  let loading = $state(true);

  // 2. Lifecycle (onMount, etc.)
  import { onMount } from 'svelte';
  onMount(() => { /* init */ });

  // 3. Functions
  async function loadData() { /* ... */ }

  // 4. Derived values
  let displayValue = $derived(data ?? '—');
</script>

<!-- Template: semantic HTML, minimal wrappers -->
<div class="card">
  <h2>🕌 Title</h2>
  <!-- ... -->
</div>

<style>
  /* Scoped styles. Use :global() sparingly — only for app-wide primitives */
  .card { /* ... */ }
</style>
```

### 3.3 The Card Pattern

The `.card` is the primary content container. Every feature tab is wrapped in one or more cards:

```svelte
<div class="card">
  <h2>📖 Feature Title</h2>
  <div class="card-body">
    <!-- content -->
  </div>
</div>
```

Cards stack vertically with `12px` (`--space-md`) margin-bottom.

### 3.4 Button System

```svelte
<!-- Primary CTA — for faith-significant actions -->
<button class="primary">Save Settings</button>

<!-- Secondary — for cancellable/optional actions -->
<button class="secondary">Cancel</button>

<!-- Tab button — navigation tab -->
<button class="tab" class:active={isActive}>
  <span class="tab-icon">🕌</span>
  <span class="tab-label">PRAYER</span>
</button>
```

**Primary button style:**
```css
button.primary {
  font-family: var(--font-display);   /* Cinzel */
  font-size: 0.82rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  padding: 10px 20px;
  background: linear-gradient(135deg, var(--gold), var(--gold-light));
  color: var(--bg);
  border-radius: 10px;
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 10px 100%, 0 calc(100% - 10px));
  /* Dipped corner is a signature FalahOS detail */
}
```

---

## 4. UX Patterns

### 4.1 Tab Navigation

The app uses a **flat tab bar** — no nested navigation, no hamburger menus, no back buttons. All features are one tap away.

```svelte
<nav class="tab-nav">
  {#each tabs as tab, i}
    <button class="tab" class:active={activeTab === i}
            onclick={() => activeTab = i}>
      <span class="tab-icon">{icons[i]}</span>
      <span class="tab-label">{tab}</span>
    </button>
  {/each}
</nav>

<main>
  {#if activeTab === 0}
    <FeatureA />
  {:else if activeTab === 1}
    <FeatureB />
  {/each}
</main>
```

**Keyboard navigation:** ArrowLeft/ArrowRight cycles tabs:
```js
function handleKeydown(e) {
  if (e.key === 'ArrowRight') activeTab = (activeTab + 1) % tabs.length;
  if (e.key === 'ArrowLeft') activeTab = (activeTab - 1 + tabs.length) % tabs.length;
}
```

### 4.2 Loading States

Every data-dependent component must handle four states:

```svelte
{#if loading}
  <div class="loading">Loading...</div>
{:else if error}
  <div class="error">{error}</div>
{:else if data}
  <!-- render content -->
{:else}
  <div class="empty">No data available</div>
{/if}
```

- **Loading:** Show a centered, subtle loading indicator (no spinners — use text or skeleton)
- **Error:** Show error message in gold/red with a retry action
- **Empty:** Show a helpful message, not a blank screen
- **Success:** Render the data

### 4.3 Notification Permissions

Prayer notification toggle uses a graceful permission flow:

```js
async function requestNotificationPermission() {
  if (!('Notification' in window)) return false;
  const perm = await Notification.requestPermission();
  if (perm === 'granted') {
    // Schedule prayer notifications
  } else if (perm === 'denied') {
    // Show a non-blocking hint about browser settings
  }
}
```

Notifications are opt-in, never assumed. The checkbox is visible but unchecked by default.

### 4.4 Data Persistence

Use `localStorage` for user preferences only. Never use it for app data.

```js
function saveMethod() {
  localStorage.setItem('prayer_method', String(method));
}

function loadSettings() {
  const saved = localStorage.getItem('prayer_method');
  if (saved) method = parseInt(saved, 10);
}
```

---

## 5. Svelte 5 Implementation

### 5.1 Runes — The Only Pattern

Use `$state` for all reactive declarations. Never use `let` alone for reactive variables.

```svelte
<script>
  // ✅ CORRECT
  let count = $state(0);
  let data = $state(null);
  let items = $state([]);

  // ❌ WRONG — not reactive
  let count = 0;
</script>
```

### 5.2 $derived

Use `$derived` for computed values that depend on state:

```svelte
<script>
  let count = $state(0);
  let double = $derived(count * 2);
</script>
```

### 5.3 $effect

Use `$effect` sparingly — only for side effects that interact with the outside world (localStorage, DOM APIs, timers):

```svelte
<script>
  let method = $state(3);

  $effect(() => {
    localStorage.setItem('prayer_method', String(method));
  });
</script>
```

**Do NOT use `$effect` for:**
- Derived values (use `$derived`)
- Event handlers (use `onclick`, `oninput`, etc.)
- Fetch calls triggered by state changes (use async functions called from events)

### 5.4 No Stores Unless Necessary

For single-page tab apps, component-local state with `$state` is sufficent. Only introduce Svelte stores (or `$state` in a shared module) when two or more unrelated components need the same reactive value.

If needed, use a `.js` module with module-level `$state`:

```js
// src/lib/stores.js
let activeTab = $state(0);
export function getActiveTab() { return activeTab; }
export function setActiveTab(n) { activeTab = n; }
```

### 5.5 Event Handling

Use modern Svelte 5 event syntax (not `on:click`):

```svelte
<!-- Svelte 5 ✅ -->
<button onclick={() => handleClick()}>Click</button>
<select onchange={(e) => method = Number(e.target.value)}>
```

### 5.6 Component Composition

Pass data down via props, never via shared mutable state:

```svelte
<ChildComponent data={prayers} onSelect={handleSelect} />
```

Props are not declared with `export let` in Svelte 5. Use `$props()`:

```svelte
<script>
  let { data, onSelect } = $props();
</script>
```

---

## 6. PWA Configuration

### 6.1 vite-plugin-pwa Setup

```js
// vite.config.js
import { VitePWA } from 'vite-plugin-pwa';

VitePWA({
  registerType: 'autoUpdate',
  manifest: {
    name: 'Nur Falah — Muslim Companion',
    short_name: 'Nur Falah',
    description: 'Your daily Islamic companion',
    theme_color: '#070A0D',
    background_color: '#070A0D',
    display: 'standalone',
    orientation: 'portrait-primary',
    icons: [
      { src: '/icon-192.png', sizes: '192x192', type: 'image/png' },
      { src: '/icon-512.png', sizes: '512x512', type: 'image/png' }
    ]
  },
  workbox: {
    globPatterns: ['**/*.{js,css,html,svg,png,woff2,ico}'],
    runtimeCaching: [
      {
        urlPattern: /^https:\/\/api\.alquran\.cloud\/.*/i,
        handler: 'StaleWhileRevalidate',
        options: {
          cacheName: 'quran-api',
          expiration: { maxEntries: 50, maxAgeSeconds: 86400 * 7 }
        }
      }
    ],
    cleanupOutdatedCaches: true
  }
})
```

### 6.2 app.html Meta

```html
<meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
<meta name="theme-color" content="#070A0D" />
<link rel="icon" type="image/svg+xml" href="/favicon.svg" />
<link rel="preconnect" href="https://api.alquran.cloud" crossorigin />
```

### 6.3 Service Worker

The `registerType: 'autoUpdate'` ensures users always get the latest version. The service worker handles:
- Pre-caching all static assets
- Runtime caching for the Quran API (7-day cache, 50 entries max)
- Cleanup of outdated caches on new versions

### 6.4 App Icons

- `icon-192.png` — 192×192px, emerald/gold brand mark
- `icon-512.png` — 512×512px, same design
- Favicon: SVG for clean rendering at any size

---

## 7. Animation & Motion

### 7.1 Principles

- **Brief:** All transitions 150-300ms
- **Purposeful:** Motion communicates state change only
- **Subtle:** No bounces, no parallax, no idle animations
- **Perf:** Use CSS `transform` and `opacity` only — never animating `width`, `height`, `top`, `left`

### 7.2 Transition Presets

```css
/* Tab hover */
.tab {
  transition: all 0.2s;
}
.tab:hover { color: var(--gold); }
.tab.active {
  color: var(--gold);
  background: var(--gold-dim);
}

/* Primary button hover */
button.primary {
  transition: transform 0.2s, box-shadow 0.2s;
}
button.primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(201, 168, 76, 0.3);
}
button.primary:active { transform: translateY(0); }

/* Secondary button */
button.secondary {
  transition: all 0.2s;
}
button.secondary:hover {
  border-color: var(--gold);
  color: var(--gold);
}
```

### 7.3 Page Transitions

For tab switching, use Svelte 5 transitions:

```svelte
{#key activeTab}
  <main transition:fade={{ duration: 200 }}>
    <!-- tab content -->
  </main>
{/key}
```

`{#key}` forces the element to re-render on tab change, triggering the transition.

---

## 8. Data & State Management

### 8.1 Local Storage Keys

| Key | Type | Purpose |
|-----|------|---------|
| `prayer_method` | number | Selected calculation method ID |
| `prayer_lat` | number | Cached latitude |
| `prayer_lng` | number | Cached longitude |
| `prayer_notifications` | boolean | Notification preference |

All keys use `snake_case` with a feature prefix.

### 8.2 External API Calls

Chain API calls carefully. Nur Falah uses the AlQuran.cloud API:

```js
async function fetchSurah(surahNumber) {
  const res = await fetch(`https://api.alquran.cloud/v1/surah/${surahNumber}`);
  if (!res.ok) throw new Error('Failed to fetch');
  return res.json();
}
```

- Always handle errors gracefully (show a user-friendly message)
- Cache API responses in the service worker (runtime caching)
- Never expose API keys in client code (this API is public)

---

## 9. Responsive Design

### 9.1 Mobile-First

```css
.app {
  max-width: 480px;
  margin: 0 auto;
  min-height: 100dvh;
}
```

The app is designed for mobile portrait. On desktop, it centers in a phone-like container. Do NOT create a separate desktop layout — the mobile experience IS the experience.

### 9.2 Safe Areas

```css
/* Use viewport-fit=cover in meta tag */
padding-bottom: 80px;        /* Tab bar clearance */
padding-left: env(safe-area-inset-left);
padding-right: env(safe-area-inset-right);
padding-bottom: env(safe-area-inset-bottom, 80px);
```

### 9.3 Touch Targets

- Tab buttons: minimum 56px wide
- Interactive elements: minimum 44×44px touch target
- Dropdowns: use native `<select>` for reliable touch behavior

---

## 10. Accessibility

### 10.1 ARIA Labels

```svelte
<button class="tab" aria-label={tab} onclick={() => activeTab = i}>
```

Every interactive element needs an `aria-label` if the visual content is icon-only.

### 10.2 Focus Management

Tab navigation uses keyboard arrows (`ArrowLeft`/`ArrowRight`). Provide a `svelte:window` handler:

```svelte
<svelte:window onkeydown={handleKeydown} />
```

### 10.3 Color Contrast

All text/background combinations exceed WCAG AA contrast:
- Gold (#C9A84C) on dark bg (#070A0D): ratio ≈ 5.8:1 ✅
- Text (#E8E6E1) on surface (#0D1117): ratio ≈ 14.0:1 ✅
- Dim text (#8B8B8B) on surface (#0D1117): ratio ≈ 5.5:1 ✅

---

## 11. Performance Budget

| Metric | Target |
|--------|--------|
| Total JS bundle (gzipped) | < 45KB |
| Total CSS (gzipped) | < 8KB |
| First paint | < 1s on 4G |
| Lighthouse PWA score | 100 |
| Offline capability | Qibla, Tasbih, Hijri, Quran (cached) |
| Service worker size | < 2KB |

### 11.1 Bundle Optimization

- No heavy UI libraries — CSS and Svelte are sufficient
- No icon libraries — use emoji for icons (zero bundle cost, universal)
- Font display: `swap` to prevent FOIT
- Preconnect to API origins

---

## 12. Project Structure

```
project-root/
├── public/
│   ├── privacy.html          # Standalone privacy page (static)
│   ├── icon-192.png
│   ├── icon-512.png
│   ├── favicon.svg
│   └── sw.js                 # Offline fallback (auto-generated by vite-plugin-pwa)
├── src/
│   ├── lib/
│   │   ├── __tests__/        # Vitest unit tests
│   │   ├── PrayerTimes.svelte
│   │   ├── Qibla.svelte
│   │   ├── Quran.svelte
│   │   ├── Hijri.svelte
│   │   ├── Tasbih.svelte
│   │   └── Names99.svelte
│   ├── App.svelte            # Main app shell (tabs, nav, footer, global styles)
│   ├── app.html              # HTML shell (fonts, meta, preconnect)
│   └── main.js               # Entry point
├── scripts/                  # Build/deploy/utility scripts
├── appstore-assets/
│   └── screenshots/          # App Store screenshot mockups
├── package.json
├── vite.config.js
└── svelte.config.js
```

### 12.1 Naming Conventions

| Artifact | Convention | Example |
|----------|------------|---------|
| Components | PascalCase.svelte | `PrayerTimes.svelte` |
| Scripts | kebab-case | `generate-docx.mjs` |
| Assets | kebab-case | `icon-192.png` |
| CSS classes | kebab-case | `.tab-nav`, `.gold-dim` |
| CSS variables | kebab-case | `--font-display` |
| JS functions | camelCase | `fetchPrayerTimes()` |
| localStorage keys | snake_case | `prayer_method` |

---

## 13. AI Agent Workflow

### 13.1 When Building a New Feature

1. **Read this guide first.** Every decision in the guide exists for consistency.
2. **Study one existing component** (e.g., `PrayerTimes.svelte`) to understand patterns before writing new code.
3. **Use the existing CSS variables** — never introduce new colors. If you need a new accent, use `--gold` or `--emerald`.
4. **One component per feature.** Features go in `src/lib/`. No subdirectories unless you have 5+ related components.
5. **Tab-based navigation.** Every new feature is a new tab in `App.svelte`. No routes, no modals, no nested views.
6. **Test offline.** Run the built app with network throttling. Core feature must work without internet.
7. **Check bundle size.** Run `npm run build` and check the dist output. Keep it under 45KB gzipped total.

### 13.2 When Modifying the Design System

- Never change `--bg`, `--text`, `--gold`, `--emerald` — these are identity-defining
- New CSS variables go in `app.html`'s global `<style>`, documented in this guide
- New fonts require an advocate — prefer extending the three existing voices

### 13.3 Deployment

Static files are built by Vite and deployed via:
1. **Docker Swarm** (primary) — nginx:alpine behind Traefik on Contabo VPS
2. **Netlify** (mirror) — direct deploy with `netlify deploy --prod --dir=dist`

### 13.4 Quick Reference: Add a New Tab

```svelte
<!-- App.svelte changes -->
<script>
  import NewFeature from './lib/NewFeature.svelte';
  const tabs = [...tabs, 'New Feature'];
  const icons = [...icons, '📱'];
</script>

<!-- Template: add condition -->
{:else if activeTab === 6}
  <NewFeature />
```

---

## 14. Checklist: New Feature

Before submitting a feature as complete, verify:

- [ ] Follows this design guide
- [ ] Uses existing CSS variables and design tokens
- [ ] Handles loading, error, empty, and success states
- [ ] Works offline (if data was previously loaded)
- [ ] Passes `npm run build` (no errors, no lint warnings)
- [ ] Bundle size increase < 5KB gzipped
- [ ] Tab navigation works with keyboard arrows
- [ ] Touch targets ≥ 44×44px
- [ ] No new colors introduced without justification
- [ ] Privacy: no data collected or transmitted
- [ ] localStorage keys use `feature_key` naming

---

> **FalahOS** — Sovereign Digital Economy. Every app built on these principles carries the same promise: private, premium, purposeful.