/* -------------------------------------------------
   ROOT VARIABLES – keep them in one place
   ------------------------------------------------- */
:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #1f2937;
    --bg-dark: #111827;
    --card-bg: rgba(31, 41, 55, .85);
    --glass-bg: rgba(255, 255, 255, .15);
    --glass-blur: blur(12px);
    --text-primary: #f3f4f6;
    --text-secondary: #d1d5db;
    --border-color: #4b5563;
    --error-color: #ef4444;
    --success-color: #22d3ee;
    --warning-color: #f59e0b;

    --sidebar-width: 280px;
    --sidebar-collapsed-width: 80px;

    --transition-fast: .3s cubic-bezier(.4,0,.2,1);
    --transition-slow: .5s cubic-bezier(.4,0,.2,1);

    --spacing-xs: .25rem;
    --spacing-sm: .5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;

    --font-size-sm: .875rem;
    --font-size-md: 1rem;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.5rem;

    --border-radius-sm: 8px;
    --border-radius-md: 12px;
    --border-radius-lg: 16px;

    --shadow-sm: 0 2px 8px rgba(0,0,0,.15);
    --shadow-md: 0 4px 20px rgba(0,0,0,.25);
}

/* -------------------------------------------------
   BASIC PAGE STYLES
   ------------------------------------------------- */
html { box-sizing: border-box; }
*, *::before, *::after { box-sizing: inherit; }

body {
    margin: 0;
    font-family: 'Inter', sans-serif;
    background: linear-gradient(135deg, #111827 0%, #1e40af 100%);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

/* -------------------------------------------------
   SIDEBAR – desktop (fixed) / mobile (off-canvas)
   ------------------------------------------------- */
.sidebar {
    position: fixed;
    top: 0; left: 0;
    width: var(--sidebar-width);
    height: 100vh;
    background: var(--secondary-color);
    transition: transform var(--transition-fast);
    z-index: 1000;
    box-shadow: 2px 0 12px rgba(0,0,0,.3);
    overflow-y: auto;
}

/* Desktop collapsed */
.sidebar.collapsed { width: var(--sidebar-collapsed-width); }

/* Mobile – start hidden */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    .sidebar.open { transform: translateX(0); }
}

/* -------------------------------------------------
   SIDEBAR HEADER & TOGGLE
   ------------------------------------------------- */
.sidebar-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg);
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-bottom: 1px solid var(--border-color);
}
.sidebar-brand {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-primary);
    text-decoration: none;
    transition: opacity var(--transition-fast);
}
.sidebar.collapsed .sidebar-brand,
.sidebar.collapsed .menu-text { opacity: 0; pointer-events: none; }

.toggle-btn {
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    font-size: var(--font-size-lg);
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: background var(--transition-fast);
}
.toggle-btn:hover { background: rgba(59,130,246,.2); }

/* Mobile toggle – always visible */
@media (max-width: 768px) {
    .toggle-btn {
        position: fixed;
        top: var(--spacing-md);
        left: var(--spacing-md);
        z-index: 1002;
        background: var(--primary-color);
        border: none;
    }
}

/* -------------------------------------------------
   SIDEBAR MENU
   ------------------------------------------------- */
.sidebar-menu { list-style: none; padding: 0; margin: var(--spacing-md) 0; }
.sidebar-menu li a {
    display: flex;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
    text-decoration: none;
    transition: all var(--transition-fast);
    min-height: 44px;
}
.sidebar-menu li a:hover,
.sidebar-menu li a.active {
    background: rgba(59,130,246,.2);
    color: var(--primary-color);
    border-left: 3px solid var(--primary-color);
}
.sidebar-menu li i {
    width: 24px;
    text-align: center;
    margin-right: var(--spacing-sm);
    flex-shrink: 0;
}
.sidebar.collapsed .menu-text { display: none; }

/* -------------------------------------------------
   MAIN CONTENT
   ------------------------------------------------- */
.main-content {
    margin-left: var(--sidebar-width);
    padding: var(--spacing-lg);
    transition: margin-left var(--transition-fast);
    min-height: 100vh;
}
.sidebar.collapsed ~ .main-content { margin-left: var(--sidebar-collapsed-width); }

@media (max-width: 768px) {
    .main-content { margin-left: 0; padding: var(--spacing-md); }
}

/* -------------------------------------------------
   BACKDROP (mobile overlay)
   ------------------------------------------------- */
body.sidebar-open::before {
    content: '';
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,.6);
    z-index: 999;
    opacity: 1;
    visibility: visible;
    transition: opacity var(--transition-fast);
}
body:not(.sidebar-open)::before { opacity: 0; visibility: hidden; }

/* -------------------------------------------------
   RESPONSIVE TYPOGRAPHY & SPACING
   ------------------------------------------------- */
@media (max-width: 480px) {
    :root {
        --spacing-lg: 1rem;
        --spacing-md: .75rem;
        --font-size-lg: 1.125rem;
        --font-size-xl: 1.25rem;
    }
    .main-content { padding: var(--spacing-sm); }
    .sidebar-menu li a { min-height: 48px; font-size: var(--font-size-md); }
}

/* -------------------------------------------------
   REUSABLE COMPONENTS
   ------------------------------------------------- */
.entity-section,
.video-form,
.video-preview,
.video-embed,
.collapsible,
.download-card,
.related-card {
    background: var(--card-bg);
    border-radius: var(--border-radius-md);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    backdrop-filter: var(--glass-blur);
}
.entity-section { opacity: 0; transform: translateY(20px); transition: opacity var(--transition-slow), transform var(--transition-slow); }
.entity-section.visible { opacity: 1; transform: translateY(0); }

.section-heading {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}
.section-heading:hover { color: var(--primary-color); }

@media (max-width: 768px) {
    .entity-section,
    .video-form,
    .video-preview,
    .video-embed,
    .collapsible,
    .download-card,
    .related-card { padding: var(--spacing-md); margin-bottom: var(--spacing-md); border-radius: var(--border-radius-sm); }
    .section-heading { font-size: var(--font-size-lg); flex-direction: column; align-items: flex-start; gap: var(--spacing-xs); }
}

/* -------------------------------------------------
   FORM CONTROLS
   ------------------------------------------------- */
.video-form .form-control {
    width: 100%;
    background: rgba(45,55,72,.95);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-md);
    min-height: 48px;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.video-form .form-control:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59,130,246,.3);
}
.video-form .form-control::placeholder { color: var(--text-secondary); }

.video-form .btn-primary {
    background: var(--primary-color);
    border: none;
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-weight: 500;
    min-height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    transition: background var(--transition-fast), transform var(--transition-fast);
    width: 100%;
}
@media (min-width: 769px) { .video-form .btn-primary { width: auto; } }
.video-form .btn-primary:hover { background: var(--primary-hover); transform: translateY(-2px); }
.video-form .btn-primary:disabled { background: var(--text-secondary); cursor: not-allowed; }

/* -------------------------------------------------
   ERROR / LOADING
   ------------------------------------------------- */
.error-message {
    color: var(--error-color);
    font-size: var(--font-size-sm);
    text-align: center;
    margin-top: var(--spacing-sm);
    padding: var(--spacing-sm);
    background: rgba(239,68,68,.2);
    border-left: 4px solid var(--error-color);
    border-radius: var(--border-radius-sm);
    opacity: 0;
    transition: opacity var(--transition-fast);
}
.error-message.active { opacity: 1; }

.loading-spinner { text-align: center; margin: var(--spacing-lg) 0; }
.spinner {
    width: 36px; height: 36px;
    border: 4px solid var(--text-primary);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin .8s linear infinite;
    margin: 0 auto var(--spacing-sm);
}
@keyframes spin { to { transform: rotate(360deg); } }

/* -------------------------------------------------
   VIDEO PREVIEW & EMBED
   ------------------------------------------------- */
.video-preview { display: flex; gap: var(--spacing-md); }
.thumbnail {
    width: 200px; flex-shrink: 0;
    border-radius: var(--border-radius-sm);
    object-fit: cover;
    transition: transform var(--transition-fast);
}
.thumbnail:hover { transform: scale(1.05); }

.video-meta h3 { font-size: var(--font-size-lg); margin-bottom: var(--spacing-sm); }
.video-meta p { margin: var(--spacing-xs) 0; color: var(--text-secondary); }
.video-meta a { color: var(--primary-color); text-decoration: none; }
.video-meta a:hover { color: var(--primary-hover); }

.video-embed iframe,
.video-embed video {
    width: 100%; aspect-ratio: 16/9;
    border-radius: var(--border-radius-sm);
    border: none;
}
@media (max-width: 768px) {
    .video-preview { flex-direction: column; }
    .thumbnail { width: 100%; max-width: 300px; }
}

/* -------------------------------------------------
   COLLAPSIBLE
   ------------------------------------------------- */
.collapsible {
    display: flex; justify-content: space-between; align-items: center;
    padding: var(--spacing-md);
    background: var(--glass-bg);
    border-radius: var(--border-radius-md);
    cursor: pointer;
    min-height: 44px;
}
.collapsible:hover { background: rgba(59,130,246,.2); }
.toggle-icon { transition: transform var(--transition-fast); }
.toggle-icon.collapsed { transform: rotate(-90deg); }

.collapsible-content {
    max-height: 2000px; overflow: hidden;
    background: var(--card-bg);
    border-radius: var(--border-radius-md);
    padding: var(--spacing-md);
    transition: max-height var(--transition-slow), opacity var(--transition-slow);
}
.collapsible-content.collapsed {
    max-height: 0; opacity: 0; padding: 0;
}
@media (max-width: 768px) {
    .collapsible { padding: var(--spacing-sm); min-height: 48px; }
    .collapsible-content { padding: var(--spacing-sm); }
}

/* -------------------------------------------------
   DOWNLOAD TABLE (desktop) / CARDS (mobile)
   ------------------------------------------------- */
.download-table {
    width: 100%; border-collapse: separate; border-spacing: 0;
    background: var(--card-bg); border-radius: var(--border-radius-md);
    overflow: hidden; box-shadow: var(--shadow-md);
    backdrop-filter: var(--glass-blur);
}
.download-table th,
.download-table td { padding: var(--spacing-md); border-bottom: 1px solid var(--border-color); }
.download-table th {
    background: var(--glass-bg);
    text-transform: uppercase;
    position: sticky; top: 0; z-index: 10;
    backdrop-filter: var(--glass-blur);
}
.download-table tr:hover td { background: rgba(59,130,246,.15); }

.download-table td a.btn {
    min-width: 44px; min-height: 44px;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-sm);
    display: inline-flex; align-items: center; justify-content: center;
}
.download-table td a.btn-primary { background: var(--primary-color); }
.download-table td a.btn-primary:hover { background: var(--primary-hover); transform: translateY(-2px); }

.desktop-only { display: table; }
.mobile-only { display: none; }

@media (max-width: 768px) {
    .desktop-only { display: none; }
    .mobile-only { display: flex; flex-direction: column; gap: var(--spacing-md); }
}

/* -------------------------------------------------
   DOWNLOAD CARDS (mobile)
   ------------------------------------------------- */
.download-card {
    border: 1px solid var(--border-color);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}
.download-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}
.download-card div {
    display: flex; justify-content: space-between; align-items: center;
    margin-bottom: var(--spacing-sm); font-size: var(--font-size-sm);
}
.download-card div span:first-child { color: var(--text-secondary); font-weight: 500; }
.download-card a.btn {
    width: 100%; text-align: center;
    padding: var(--spacing-md);
    min-height: 48px;
    display: inline-flex; align-items: center; justify-content: center;
}
.download-card a.btn-primary { background: var(--primary-color); }
.download-card a.btn-primary:hover { background: var(--primary-hover); transform: translateY(-2px); }

/* -------------------------------------------------
   RELATED VIDEOS GRID
   ------------------------------------------------- */
.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--spacing-md);
    padding: var(--spacing-md);
}
@media (max-width: 768px) {
    .related-grid { grid-template-columns: 1fr; padding: var(--spacing-sm); }
}
.related-card {
    display: block; text-decoration: none;
    overflow: hidden;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}
.related-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}
.related-card img {
    width: 100%; height: 120px; object-fit: cover;
    border-radius: var(--border-radius-sm) var(--border-radius-sm) 0 0;
}
.related-card .card-body { padding: var(--spacing-md); }
.related-card h4 { font-size: var(--font-size-sm); margin: 0; color: var(--text-primary); }