/* ==========================================================================
   GCSE Arabic Dual-Language Revision Platform - Universal Design System
   ========================================================================== */

/* ==========================================================================
   Dubai Font Web Access (via jsDelivr CDN)
   Ensures 'Dubai Light' and 'Dubai' are 100% accessible across all web clients
   ========================================================================== */

@font-face {
    font-family: 'Dubai Light';
    src: local('Dubai Light'), local('Dubai-Light'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.ttf') format('truetype');
    font-weight: 300;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Dubai Light';
    src: local('Dubai Light'), local('Dubai-Light'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.ttf') format('truetype');
    font-weight: 400;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Dubai';
    src: local('Dubai Light'), local('Dubai-Light'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Light.ttf') format('truetype');
    font-weight: 300;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Dubai';
    src: local('Dubai Regular'), local('Dubai-Regular'), local('Dubai'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Regular.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Regular.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Regular.ttf') format('truetype');
    font-weight: 400;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Dubai';
    src: local('Dubai Medium'), local('Dubai-Medium'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Medium.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Medium.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Medium.ttf') format('truetype');
    font-weight: 500;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Dubai';
    src: local('Dubai Bold'), local('Dubai-Bold'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Bold.woff2') format('woff2'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Bold.woff') format('woff'),
         url('https://cdn.jsdelivr.net/npm/dubai-font@1.1.1/dubai-font/fonts/Dubai-Bold.ttf') format('truetype');
    font-weight: 700;
    font-style: normal;
    font-display: swap;
}

:root {
    --bg-base: #f8fafc;
    --bg-mesh-1: rgba(99, 102, 241, 0.08);
    --bg-mesh-2: rgba(168, 85, 247, 0.08);
    --surface-card: rgba(255, 255, 255, 0.88);
    --surface-card-hover: #ffffff;
    --surface-card-en: rgba(240, 249, 255, 0.94);
    --surface-card-both: rgba(250, 245, 255, 0.94);
    --surface-glass: rgba(255, 255, 255, 0.82);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --accent-primary: #6366f1;
    --accent-secondary: #8b5cf6;
    --accent-en: #0284c7;
    --accent-both: #9333ea;
    --accent-en-glow: rgba(2, 132, 199, 0.18);
    --accent-both-glow: rgba(147, 51, 234, 0.18);
    --accent-glow: rgba(99, 102, 241, 0.25);
    --border-subtle: rgba(226, 232, 240, 0.85);
    --border-focus: rgba(99, 102, 241, 0.5);
    --border-en: rgba(2, 132, 199, 0.4);
    --border-both: rgba(147, 51, 234, 0.4);
    --shadow-soft: 0 4px 20px -2px rgba(15, 23, 42, 0.04), 0 2px 6px -1px rgba(15, 23, 42, 0.02);
    --shadow-float: 0 20px 40px -15px rgba(15, 23, 42, 0.08);
    --arabic-size: 1.65rem;
    --english-size: 1.08rem;
    --ui-font: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    --arabic-font: 'Dubai Light', 'Dubai', 'Amiri', 'Traditional Arabic', serif;
}

[data-theme="dark"] {
    --bg-base: #090d16;
    --bg-mesh-1: rgba(99, 102, 241, 0.12);
    --bg-mesh-2: rgba(168, 85, 247, 0.12);
    --surface-card: rgba(17, 24, 39, 0.82);
    --surface-card-hover: rgba(30, 41, 59, 0.96);
    --surface-card-en: rgba(12, 29, 49, 0.90);
    --surface-card-both: rgba(29, 18, 49, 0.90);
    --surface-glass: rgba(15, 23, 42, 0.82);
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    --accent-primary: #818cf8;
    --accent-secondary: #a78bfa;
    --accent-en: #38bdf8;
    --accent-both: #c084fc;
    --accent-en-glow: rgba(56, 189, 248, 0.2);
    --accent-both-glow: rgba(192, 132, 252, 0.2);
    --accent-glow: rgba(129, 140, 248, 0.2);
    --border-subtle: rgba(51, 65, 85, 0.55);
    --border-focus: rgba(129, 140, 248, 0.6);
    --border-en: rgba(56, 189, 248, 0.5);
    --border-both: rgba(192, 132, 252, 0.5);
    --shadow-soft: 0 4px 20px -2px rgba(0, 0, 0, 0.35);
    --shadow-float: 0 20px 40px -15px rgba(0, 0, 0, 0.55);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0; padding: 0;
    font-family: var(--arabic-font);
    background-color: var(--bg-base);
    background-image: 
        radial-gradient(at 0% 0%, var(--bg-mesh-1) 0px, transparent 50%),
        radial-gradient(at 100% 100%, var(--bg-mesh-2) 0px, transparent 50%);
    background-attachment: fixed;
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
}

/* --- Universal Top App Bar --- */
.site-header {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 56px;
    z-index: 700;
    display: flex; align-items: center; justify-content: space-between;
    padding: 0 24px;
    background: var(--surface-glass);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-subtle);
    box-shadow: var(--shadow-soft);
    font-family: var(--ui-font);
    direction: ltr;
}

.nav-left-group {
    display: flex; align-items: center; gap: 18px;
}

.site-logo {
    display: flex; align-items: center; gap: 10px;
    text-decoration: none;
    font-weight: 800;
    font-size: 0.98rem;
    color: var(--text-primary);
    letter-spacing: -0.02em;
    transition: transform 0.15s ease;
}
.site-logo:hover { transform: scale(1.02); }

.brand-dot {
    width: 11px; height: 11px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    box-shadow: 0 0 10px var(--accent-primary);
}

.site-nav-breadcrumb {
    display: flex; align-items: center; gap: 8px;
    font-size: 0.82rem;
    color: var(--text-muted);
}
.site-nav-breadcrumb a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.15s ease;
}
.site-nav-breadcrumb a:hover { color: var(--accent-primary); }
.site-nav-breadcrumb .divider { color: var(--border-subtle); }
.site-nav-breadcrumb .current-page {
    color: var(--text-primary);
    font-weight: 700;
}

/* Quick Jump Dropdowns */
.nav-center-group {
    display: flex; align-items: center; gap: 10px;
}
.quick-jump-select {
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    color: var(--text-primary);
    font-family: var(--ui-font);
    font-size: 0.78rem;
    font-weight: 600;
    padding: 6px 12px;
    border-radius: 10px;
    cursor: pointer;
    outline: none;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}
.quick-jump-select:hover, .quick-jump-select:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 8px var(--accent-glow);
}

.nav-right-group {
    display: flex; align-items: center; gap: 10px;
}

.btn-nav-search {
    display: flex; align-items: center; gap: 8px;
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    font-family: var(--ui-font);
    font-size: 0.78rem;
    font-weight: 600;
    padding: 6px 14px;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s ease;
}
.btn-nav-search:hover {
    border-color: var(--accent-primary);
    color: var(--text-primary);
    box-shadow: 0 0 8px var(--accent-glow);
}
.btn-nav-search kbd {
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    border-radius: 4px;
    padding: 1px 5px;
    font-size: 0.65rem;
    color: var(--text-muted);
}

.theme-toggle {
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    width: 34px; height: 34px;
    border-radius: 10px;
    cursor: pointer;
    display: flex; align-items: center; justify-content: center;
    font-size: 1rem;
    transition: all 0.2s ease;
}
.theme-toggle:hover {
    transform: scale(1.05);
    color: var(--accent-primary);
    border-color: var(--border-focus);
}

.mobile-hamburger {
    display: none;
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    color: var(--text-primary);
    width: 36px; height: 36px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 1.15rem;
    align-items: center; justify-content: center;
}

/* Mobile Slide-Down Drawer */
.mobile-nav-drawer {
    display: none;
    position: fixed;
    top: 56px; left: 0; width: 100%;
    max-height: calc(100vh - 56px);
    overflow-y: auto;
    background: var(--surface-glass);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border-bottom: 1px solid var(--border-subtle);
    padding: 18px 20px 32px 20px;
    z-index: 699;
    font-family: var(--ui-font);
    box-shadow: var(--shadow-float);
    direction: ltr;
}
.mobile-nav-drawer.open { display: block; }
.mobile-drawer-section-title {
    font-size: 0.7rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin: 14px 0 8px 0;
}
.mobile-drawer-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}
.mobile-drawer-link {
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    padding: 9px 12px;
    border-radius: 10px;
    text-decoration: none;
    color: var(--text-primary);
    font-size: 0.82rem;
    font-weight: 600;
    display: flex; align-items: center; justify-content: space-between;
}
.mobile-drawer-link:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

/* --- Progress Bar --- */
.progress-container {
    position: fixed;
    top: 56px; left: 0; width: 100%; height: 3px;
    background: transparent;
    z-index: 650;
}
.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));
    width: 0%;
    transition: width 0.1s ease-out;
    box-shadow: 0 0 10px var(--accent-glow);
}

/* --- Floating Sidebar (Offset below Top Bar) --- */
.nav-pane {
    position: fixed;
    top: 76px; left: 20px;
    width: 295px;
    height: calc(100vh - 96px);
    background: var(--surface-glass);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-subtle);
    border-radius: 24px;
    padding: 16px;
    direction: ltr;
    font-family: var(--ui-font);
    box-shadow: var(--shadow-float);
    display: flex; flex-direction: column;
    z-index: 100;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.nav-header {
    display: flex; align-items: center; justify-content: space-between;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-subtle);
    margin-bottom: 10px;
}
.brand-badge {
    display: flex; align-items: center; gap: 8px;
    font-weight: 800; font-size: 0.82rem;
    color: var(--text-primary);
    letter-spacing: -0.01em;
}
.nav-pane .nav-header .theme-toggle {
    display: none; /* Removed duplicate theme toggle; managed globally in top app bar */
}

.controls-box {
    background: var(--surface-card);
    border: 1px solid var(--border-subtle);
    padding: 10px 12px;
    border-radius: 14px;
    margin-bottom: 10px;
}
.controls-label {
    font-size: 0.66rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    font-weight: 700;
    margin-bottom: 6px;
    display: flex; justify-content: space-between; align-items: center;
}
.font-slider {
    width: 100%;
    accent-color: var(--accent-primary);
    cursor: pointer;
    margin: 0;
}

.lang-actions {
    display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 5px;
}
.trigger-actions {
    display: grid; grid-template-columns: 1fr 1fr; gap: 5px;
    margin-top: 6px;
}
.lang-btn {
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    font-family: var(--ui-font);
    font-size: 0.72rem;
    font-weight: 600;
    padding: 6px 4px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.18s ease;
    white-space: nowrap;
}
.lang-btn:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}
.lang-btn.active-mode {
    background: var(--accent-primary);
    color: #fff;
    border-color: var(--accent-primary);
}
.lang-btn.active-both {
    background: var(--accent-both);
    color: #fff;
    border-color: var(--accent-both);
}
.control-divider {
    height: 1px;
    border-top: 1px dashed var(--border-subtle);
    margin: 9px 0 7px 0;
}
.checkbox-row {
    display: flex; align-items: center; gap: 9px;
    margin-top: 8px; padding-top: 8px;
    border-top: 1px dashed var(--border-subtle);
    cursor: pointer;
    font-size: 0.76rem; font-weight: 600;
    color: var(--text-primary);
    user-select: none;
}
.checkbox-row input[type="checkbox"] {
    width: 15px; height: 15px;
    accent-color: var(--accent-both);
    cursor: pointer; margin: 0;
    border-radius: 4px;
}
.layout-suboptions {
    display: none;
    grid-template-columns: 1fr 1fr; gap: 5px;
    margin-top: 7px;
}
.layout-suboptions.visible { display: grid; }

.nav-links-container {
    overflow-y: auto; flex: 1;
    padding-right: 4px; margin-top: 2px;
}
.nav-links-container::-webkit-scrollbar { width: 4px; }
.nav-links-container::-webkit-scrollbar-thumb {
    background: var(--border-subtle); border-radius: 4px;
}
.nav-pane ul { list-style-type: none; padding: 0; margin: 0; }
.nav-pane li { margin-bottom: 3px; }
.nav-pane a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.78rem; font-weight: 500;
    display: flex; align-items: center;
    padding: 7px 10px; border-radius: 10px;
    transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
    border: 1px solid transparent;
    line-height: 1.35;
    word-break: break-word;
}
.nav-pane a:hover {
    background-color: var(--surface-card);
    color: var(--text-primary);
    transform: translateX(4px);
}
.nav-pane a.active {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.12), rgba(168, 85, 247, 0.12));
    color: var(--accent-primary);
    font-weight: 600;
    border-color: var(--border-focus);
}
.nav-group-title {
    font-weight: 700; color: var(--text-muted);
    margin-top: 2px; margin-bottom: 6px;
    text-transform: uppercase; font-size: 0.65rem;
    letter-spacing: 0.08em; padding-left: 12px;
}

/* --- Main Content Area --- */
.main-content {
    margin-left: 350px; margin-right: auto;
    padding: 86px 40px 140px 40px;
    max-width: 960px;
    direction: rtl;
}

.hero-banner {
    background: var(--surface-card);
    backdrop-filter: blur(12px);
    border: 1px solid var(--border-subtle);
    border-radius: 28px;
    padding: 42px 36px;
    text-align: center;
    margin-bottom: 44px;
    box-shadow: var(--shadow-soft);
    position: relative; overflow: hidden;
    direction: ltr;
    font-family: var(--ui-font);
}
.hero-banner::before {
    content: ""; position: absolute;
    top: -50%; left: -50%; width: 200%; height: 200%;
    background: radial-gradient(circle, var(--accent-glow) 0%, transparent 60%);
    opacity: 0.4; pointer-events: none;
}
.hero-pill {
    display: inline-block;
    padding: 6px 14px;
    background: rgba(99, 102, 241, 0.1);
    color: var(--accent-primary);
    border: 1px solid var(--border-focus);
    border-radius: 999px;
    font-size: 0.75rem; font-weight: 700;
    letter-spacing: 0.06em; text-transform: uppercase;
    margin-bottom: 14px;
}
.main-title {
    font-size: 2.15rem; font-weight: 800;
    color: var(--text-primary);
    margin: 0 0 8px 0;
    letter-spacing: -0.03em; line-height: 1.2;
}
.author {
    font-size: 1.05rem; color: var(--text-secondary);
    margin: 0; font-weight: 600;
}
.interaction-hint {
    margin-top: 18px;
    font-size: 0.8rem; color: var(--text-secondary);
    display: inline-flex; align-items: center; gap: 8px;
    background: var(--bg-base);
    padding: 8px 16px; border-radius: 12px;
    border: 1px solid var(--border-focus);
    font-weight: 600;
    box-shadow: 0 2px 10px var(--accent-glow);
}

.section-title {
    font-size: 1.15rem; font-weight: 700;
    text-align: left;
    margin-top: 3.5rem; margin-bottom: 0.5rem;
    color: var(--text-primary);
    direction: ltr; font-family: var(--ui-font);
    display: flex; align-items: center; gap: 12px;
    scroll-margin-top: 76px;
}
.section-title::before {
    content: ""; display: inline-block;
    width: 12px; height: 24px; border-radius: 6px;
    background: linear-gradient(180deg, var(--accent-primary), var(--accent-secondary));
}
.section-meta {
    margin: 0 0 1.25rem 0;
    color: var(--text-muted);
    direction: ltr;
    font: 600 0.8rem/1.45 var(--ui-font);
}

/* Sub-question / Prompt Divider for Listening Papers */
.subquestion-divider {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 32px 0 16px 0;
    padding: 10px 18px;
    background: var(--surface-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-subtle);
    border-left: 4px solid var(--accent-primary);
    border-radius: 14px;
    box-shadow: var(--shadow-soft);
    direction: ltr;
    text-align: left;
    font-family: var(--ui-font);
}
.subquestion-divider-badge {
    background: rgba(99, 102, 241, 0.12);
    color: var(--accent-primary);
    border: 1px solid var(--border-focus);
    padding: 3px 10px;
    border-radius: 999px;
    font-size: 0.7rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    flex-shrink: 0;
}
.subquestion-divider-text {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* --- Interactive Dual-Language Cards --- */
.paragraph {
    margin-bottom: 16px;
    background-color: var(--surface-card);
    backdrop-filter: blur(8px);
    padding: 32px 34px 26px 34px;
    border-radius: 20px;
    box-shadow: var(--shadow-soft);
    border: 1px solid var(--border-subtle);
    transition: transform 0.22s cubic-bezier(0.16, 1, 0.3, 1),
                background-color 0.25s ease,
                border-color 0.25s ease,
                box-shadow 0.25s ease,
                opacity 0.14s ease;
    cursor: pointer;
    position: relative;
    user-select: none;
}
.paragraph:hover {
    transform: translateY(-2px);
    background-color: var(--surface-card-hover);
    border-color: var(--border-focus);
    box-shadow: var(--shadow-float);
}

/* Pre-line white space for dialogues */
.lang-ar {
    direction: rtl; text-align: right;
    font-family: var(--arabic-font);
    font-size: var(--arabic-size);
    line-height: 2.05;
    color: var(--text-primary);
    white-space: pre-line;
}
.lang-en {
    direction: ltr; text-align: left;
    font-family: var(--ui-font);
    font-size: var(--english-size);
    line-height: 1.7;
    color: var(--text-primary);
    white-space: pre-line;
}
.lang-divider { display: none; }

.paragraph[data-state="ar"] .lang-en { display: none; }
.paragraph[data-state="en"] {
    background-color: var(--surface-card-en);
    border-color: var(--border-en);
    box-shadow: 0 4px 20px -2px var(--accent-en-glow);
}
.paragraph[data-state="en"] .lang-ar { display: none; }
.paragraph[data-state="both"] {
    background-color: var(--surface-card-both);
    border-color: var(--border-both);
    box-shadow: 0 4px 20px -2px var(--accent-both-glow);
}
.paragraph[data-state="both"] .lang-en { color: var(--text-secondary); }

body[data-combined-layout="stacked"] .paragraph[data-state="both"] .lang-divider {
    display: block; height: 1px;
    background: linear-gradient(90deg, transparent, var(--border-both), transparent);
    margin: 16px 0; opacity: 0.6;
}

body[data-combined-layout="split"] .paragraph[data-state="both"] {
    display: grid; grid-template-columns: 1fr 1px 1fr;
    gap: 24px; align-items: center; direction: rtl;
}
body[data-combined-layout="split"] .paragraph[data-state="both"] .lang-divider {
    display: block; width: 1px; height: 100%;
    background: var(--border-both); opacity: 0.45;
}

.paragraph::after {
    content: attr(data-badge);
    position: absolute; top: 10px; left: 14px;
    font-family: var(--ui-font);
    font-size: 0.64rem; font-weight: 700; letter-spacing: 0.05em;
    padding: 3px 9px; border-radius: 999px;
    background: rgba(99, 102, 241, 0.1);
    color: var(--accent-primary);
    border: 1px solid var(--border-focus);
    transition: all 0.2s ease;
    direction: ltr;
}
body[data-trigger-mode="click"][data-combine-mode="false"] .paragraph[data-state="ar"]:hover::after { content: "↻ Click for EN"; }
body[data-trigger-mode="click"][data-combine-mode="true"] .paragraph[data-state="ar"]:hover::after { content: "↻ Click for AR + EN"; }
body[data-trigger-mode="click"] .paragraph[data-state="both"]:hover::after { content: "↻ Click for AR only"; }
body[data-trigger-mode="click"] .paragraph[data-state="en"]:hover::after { content: "↻ Click for AR"; }
.paragraph[data-state="both"]::after {
    background: rgba(147, 51, 234, 0.12);
    color: var(--accent-both); border-color: var(--border-both);
}
.paragraph[data-state="en"]::after {
    left: auto; right: 14px;
    background: rgba(2, 132, 199, 0.12);
    color: var(--accent-en); border-color: var(--border-en);
}
.paragraph.flipping { opacity: 0.35; transform: scale(0.988); }

.paragraph:focus-visible, .theme-toggle:focus-visible, .lang-btn:focus-visible, .font-slider:focus-visible, .nav-pane a:focus-visible, .quick-jump-select:focus-visible {
    outline: 3px solid var(--accent-primary); outline-offset: 3px;
}

@media (hover: none) {
    .hover-only { display: none; }
    .trigger-actions { grid-template-columns: 1fr; }
}

/* Mobile Responsiveness for Reader */
.mobile-sections-toggle { display: none; }
@media (max-width: 960px) {
    .site-nav-breadcrumb { display: none; }
    .nav-center-group { display: none; }
    .mobile-hamburger { display: flex; }
    
    .nav-pane {
        position: relative; top: 0; left: 0;
        width: calc(100% - 32px); margin: 76px auto 16px auto;
        height: auto; max-height: none;
        backdrop-filter: none; -webkit-backdrop-filter: none;
    }
    .main-content {
        margin-left: auto; padding: 16px 20px 80px 20px;
    }
    .hero-banner { padding: 32px 20px; }
    .main-title { font-size: 1.6rem; }
    .paragraph { padding: 30px 22px 22px 22px; }
    
    .nav-links-container {
        position: fixed; right: 16px; bottom: 16px; z-index: 200;
        width: min(300px, calc(100vw - 32px)); margin: 0; flex: 0; overflow: visible;
    }
    .mobile-sections-toggle {
        width: 100%; display: flex; align-items: center; justify-content: space-between;
        padding: 12px 14px; border: 1px solid var(--border-subtle); border-radius: 12px;
        background: var(--surface-card); color: var(--text-primary);
        font: 700 0.8rem var(--ui-font); cursor: pointer;
        box-shadow: var(--shadow-float); backdrop-filter: blur(12px);
    }
    .mobile-sections-chevron { transition: transform 0.2s ease; }
    .nav-pane.sections-open .mobile-sections-chevron { transform: rotate(180deg); }
    .nav-pane:not(.sections-open) .nav-links-container ul { display: none; }
    .nav-pane.sections-open .nav-links-container ul {
        position: absolute; right: 0; bottom: calc(100% + 8px);
        display: block; width: 100%; max-height: min(60vh, 420px);
        overflow-y: auto; margin: 0; padding: 8px 4px 8px 0;
        border: 1px solid var(--border-subtle); border-radius: 14px;
        background: var(--surface-glass); box-shadow: var(--shadow-float);
        backdrop-filter: blur(18px);
    }
}

@media (max-width: 640px) {
    body[data-combined-layout="split"] .paragraph[data-state="both"] {
        grid-template-columns: 1fr; gap: 12px;
    }
    body[data-combined-layout="split"] .paragraph[data-state="both"] .lang-divider {
        width: 100%; height: 1px;
    }
}

/* ==========================================================================
   HOMEPAGE (HUB) EXCLUSIVE STYLES
   ========================================================================== */
.hub-page {
    font-family: var(--ui-font);
    direction: ltr;
}
.hub-container {
    max-width: 1200px;
    margin: 80px auto 100px auto;
    padding: 0 24px;
}
.hub-hero {
    background: var(--surface-card);
    backdrop-filter: blur(16px);
    border: 1px solid var(--border-subtle);
    border-radius: 32px;
    padding: 56px 40px;
    text-align: center;
    position: relative; overflow: hidden;
    box-shadow: var(--shadow-soft);
    margin-bottom: 36px;
}
.hub-hero::before {
    content: ""; position: absolute;
    top: -50%; left: -50%; width: 200%; height: 200%;
    background: radial-gradient(circle, var(--accent-glow) 0%, transparent 60%);
    opacity: 0.45; pointer-events: none;
}
.hub-badge {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 7px 18px;
    background: rgba(99, 102, 241, 0.1);
    color: var(--accent-primary);
    border: 1px solid var(--border-focus);
    border-radius: 999px;
    font-size: 0.78rem; font-weight: 700;
    letter-spacing: 0.06em; text-transform: uppercase;
    margin-bottom: 18px;
}
.hub-title {
    font-size: 2.75rem; font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.03em; line-height: 1.15;
    margin: 0 0 14px 0;
}
.hub-title-gradient {
    background: linear-gradient(135deg, var(--accent-primary) 20%, var(--accent-secondary) 80%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}
.hub-subtitle {
    font-size: 1.15rem; color: var(--text-secondary);
    max-width: 720px; margin: 0 auto 28px auto;
    line-height: 1.6;
}
.hub-stats-row {
    display: flex; justify-content: center; flex-wrap: wrap; gap: 14px;
    margin-bottom: 32px;
}
.stat-pill {
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    padding: 8px 16px; border-radius: 999px;
    font-size: 0.82rem; font-weight: 600;
    color: var(--text-secondary);
    display: flex; align-items: center; gap: 8px;
}
.stat-pill strong { color: var(--text-primary); }

/* Search Bar on Hub */
.hub-search-box {
    max-width: 640px; margin: 0 auto;
    position: relative;
}
.hub-search-input {
    width: 100%;
    padding: 16px 20px 16px 48px;
    font-family: var(--ui-font);
    font-size: 0.95rem; font-weight: 500;
    border-radius: 18px;
    border: 1px solid var(--border-subtle);
    background: var(--surface-glass);
    color: var(--text-primary);
    outline: none;
    box-shadow: var(--shadow-soft);
    transition: all 0.25s ease;
}
.hub-search-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 4px var(--accent-glow);
    background: var(--surface-card);
}
.hub-search-icon {
    position: absolute; left: 18px; top: 50%;
    transform: translateY(-50%);
    font-size: 1.1rem; color: var(--text-muted);
    pointer-events: none;
}

/* Unified Hub Toolbar & Filter Station */
.hub-toolbar-card {
    background: var(--surface-card);
    backdrop-filter: blur(14px);
    border: 1px solid var(--border-subtle);
    border-radius: 20px;
    padding: 18px 22px;
    box-shadow: var(--shadow-soft);
    margin-bottom: 28px;
    display: flex;
    flex-direction: column;
    gap: 14px;
}
.toolbar-header {
    display: flex;
    align-items: center;
    justify-content: flex-start;
}
.view-mode-tabs {
    display: inline-flex; gap: 6px;
    background: var(--bg-base);
    padding: 5px; border-radius: 14px;
    border: 1px solid var(--border-subtle);
}
.view-tab-btn {
    border: none; background: transparent;
    padding: 8px 16px; border-radius: 10px;
    font-family: var(--ui-font); font-size: 0.82rem; font-weight: 700;
    color: var(--text-secondary); cursor: pointer;
    transition: all 0.2s ease;
}
.view-tab-btn.active {
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    color: #fff;
    box-shadow: 0 4px 12px var(--accent-glow);
}

.toolbar-filters {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 12px;
    padding-top: 14px;
    border-top: 1px solid var(--border-subtle);
}
.filter-group {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 6px;
}
.filter-group-label {
    font-size: 0.72rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-right: 4px;
}
.filter-pills-wrap {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 6px;
}
.filter-divider {
    height: 22px;
    width: 1px;
    background: var(--border-subtle);
    margin: 0 4px;
}
.filter-pill {
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    font-family: var(--ui-font);
    font-size: 0.76rem; font-weight: 600;
    padding: 6px 13px; border-radius: 999px;
    cursor: pointer; transition: all 0.18s ease;
}
.filter-pill:hover { border-color: var(--accent-primary); color: var(--accent-primary); }
.filter-pill.active {
    background: var(--accent-primary);
    color: #fff; border-color: var(--accent-primary);
}

@media (max-width: 768px) {
    .filter-divider { display: none; }
    .hub-toolbar-card { padding: 14px; }
    .toolbar-filters { flex-direction: column; align-items: flex-start; gap: 10px; }
}

/* Grid View 1: Series Cards (By Year) */
.series-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(360px, 1fr));
    gap: 24px;
}
.series-card {
    background: var(--surface-card);
    backdrop-filter: blur(14px);
    border: 1px solid var(--border-subtle);
    border-radius: 24px;
    padding: 26px;
    box-shadow: var(--shadow-soft);
    transition: transform 0.22s ease, box-shadow 0.22s ease, border-color 0.22s ease;
}
.series-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-float);
    border-color: var(--border-focus);
}
.series-card-header {
    display: flex; justify-content: space-between; align-items: flex-start;
    margin-bottom: 12px;
}
.series-year-badge {
    font-size: 1.25rem; font-weight: 800;
    color: var(--text-primary);
}
.series-session-tag {
    font-size: 0.72rem; font-weight: 700;
    padding: 4px 10px; border-radius: 999px;
    background: rgba(99, 102, 241, 0.1);
    color: var(--accent-primary);
    border: 1px solid var(--border-focus);
}
.series-desc {
    font-size: 0.82rem; color: var(--text-secondary);
    margin: 0 0 18px 0; line-height: 1.45;
}
.series-papers-label {
    font-size: 0.68rem; font-weight: 700;
    text-transform: uppercase; letter-spacing: 0.08em;
    color: var(--text-muted); margin-bottom: 10px;
}
.series-papers-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}
.paper-cell-btn {
    text-decoration: none;
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    border-radius: 12px;
    padding: 10px 6px;
    text-align: center;
    transition: all 0.18s ease;
    display: flex; flex-direction: column; align-items: center; gap: 3px;
}
.paper-cell-btn:hover {
    transform: translateY(-2px);
    border-color: var(--accent-primary);
    background: var(--surface-card-hover);
    box-shadow: 0 4px 12px var(--accent-glow);
}
.paper-cell-btn.disabled {
    opacity: 0.45; pointer-events: none;
    border-style: dashed;
}
.paper-code-tag {
    font-size: 0.85rem; font-weight: 800;
    color: var(--text-primary);
}
.paper-skill-tag {
    font-size: 0.68rem; font-weight: 600;
    color: var(--text-muted);
    white-space: nowrap;
    letter-spacing: -0.01em;
}

/* Grid View 2: By Skill / Component */
.skills-container {
    display: flex; flex-direction: column; gap: 36px;
}
.skill-block {
    background: var(--surface-card);
    backdrop-filter: blur(14px);
    border: 1px solid var(--border-subtle);
    border-radius: 28px;
    padding: 30px;
    box-shadow: var(--shadow-soft);
}
.skill-block-header {
    display: flex; align-items: center; gap: 14px;
    margin-bottom: 20px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border-subtle);
}
.skill-block-icon {
    font-size: 2rem;
    width: 48px; height: 48px; border-radius: 14px;
    display: flex; align-items: center; justify-content: center;
    background: rgba(99, 102, 241, 0.1);
}
.skill-block-title {
    font-size: 1.35rem; font-weight: 800;
    color: var(--text-primary); margin: 0;
}
.skill-block-desc {
    font-size: 0.82rem; color: var(--text-secondary); margin: 2px 0 0 0;
}
.skill-papers-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 12px;
}
.skill-paper-card {
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    border-radius: 14px;
    padding: 14px 16px;
    text-decoration: none;
    display: flex; justify-content: space-between; align-items: center;
    transition: all 0.18s ease;
}
.skill-paper-card:hover {
    transform: translateX(4px);
    border-color: var(--accent-primary);
    background: var(--surface-card-hover);
    box-shadow: 0 4px 14px var(--accent-glow);
}
.skill-paper-info {
    display: flex; flex-direction: column; gap: 2px;
}
.skill-paper-year {
    font-size: 0.88rem; font-weight: 700; color: var(--text-primary);
}
.skill-paper-tier {
    font-size: 0.72rem; font-weight: 600; color: var(--text-muted);
}
.skill-paper-arrow {
    color: var(--accent-primary); font-size: 1rem; font-weight: 700;
}

/* Grid View 3: Specification Themes Explorer */
.themes-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(360px, 1fr));
    gap: 24px;
}
.theme-card {
    background: var(--surface-card);
    backdrop-filter: blur(14px);
    border: 1px solid var(--border-subtle);
    border-radius: 24px;
    padding: 26px;
    box-shadow: var(--shadow-soft);
}
.theme-card-num {
    font-size: 0.72rem; font-weight: 800;
    text-transform: uppercase; letter-spacing: 0.08em;
    color: var(--accent-primary); margin-bottom: 6px;
}
.theme-card-title {
    font-size: 1.15rem; font-weight: 800;
    color: var(--text-primary); margin: 0 0 10px 0;
}
.theme-card-subtopics {
    font-size: 0.8rem; color: var(--text-secondary);
    line-height: 1.5; margin-bottom: 16px;
}
.theme-papers-count {
    font-size: 0.75rem; font-weight: 700;
    padding: 6px 12px; border-radius: 999px;
    background: var(--bg-base);
    border: 1px solid var(--border-subtle);
    display: inline-block;
    color: var(--text-primary);
}

/* Recently Viewed Section */
.recent-section {
    margin-top: 48px;
    padding-top: 36px;
    border-top: 1px solid var(--border-subtle);
}
.recent-title {
    font-size: 1.1rem; font-weight: 800;
    color: var(--text-primary); margin: 0 0 16px 0;
    display: flex; align-items: center; gap: 8px;
}
.recent-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 14px;
}

/* Global Quick Search Modal */
.search-modal-backdrop {
    display: none;
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(9, 13, 22, 0.6);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    z-index: 1000;
    align-items: flex-start; justify-content: center;
    padding-top: 100px;
}
.search-modal-backdrop.open { display: flex; }
.search-modal-window {
    width: min(640px, calc(100vw - 32px));
    background: var(--surface-card);
    border: 1px solid var(--border-focus);
    border-radius: 24px;
    box-shadow: var(--shadow-float);
    overflow: hidden;
    font-family: var(--ui-font);
    direction: ltr;
}
.search-modal-header {
    display: flex; align-items: center; gap: 12px;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-subtle);
}
.search-modal-input {
    flex: 1; border: none; background: transparent;
    font-family: var(--ui-font); font-size: 1.05rem; font-weight: 600;
    color: var(--text-primary); outline: none;
}
.search-modal-close {
    border: none; background: transparent;
    font-size: 1.1rem; color: var(--text-muted); cursor: pointer;
}
.search-modal-results {
    max-height: 400px; overflow-y: auto; padding: 12px;
}
.search-result-item {
    padding: 12px 14px; border-radius: 12px;
    text-decoration: none; color: var(--text-primary);
    display: flex; justify-content: space-between; align-items: center;
    transition: background-color 0.15s ease;
}
.search-result-item:hover {
    background: var(--bg-base);
}
.search-result-title {
    font-size: 0.88rem; font-weight: 700;
}
.search-result-meta {
    font-size: 0.74rem; color: var(--text-muted);
}