/* CSS Reset & Variables */
:root {
    --bg-app: #f5f7fa;
    --bg-sidebar: #ffffff;
    --bg-panel: #ffffff;
    --border-color: #e6e9f0;
    --text-primary: #1e293b;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    
    --accent-color: #4f46e5;
    --accent-color-hover: #4338ca;
    --accent-soft: rgba(79, 70, 229, 0.06);
    --accent-soft-hover: rgba(79, 70, 229, 0.12);
    
    --success-color: #10b981;
    --success-soft: rgba(16, 185, 129, 0.08);
    
    --shadow-sm: 0 2px 4px rgba(15, 23, 42, 0.04);
    --shadow-md: 0 8px 16px rgba(15, 23, 42, 0.06);
    --shadow-lg: 0 16px 24px rgba(15, 23, 42, 0.08);
    
    --card-bg: #ffffff;
    --card-bg-hover: #fafbfc;
    
    --topic-selected-bg: #f5f6ff;
    --topic-selected-border: #c7d2fe;
    
    --glass-bg: rgba(255, 255, 255, 0.75);
    --glass-border: rgba(255, 255, 255, 0.5);
    
    --scrollbar-thumb: #cbd5e1;
    --scrollbar-track: #f1f5f9;
}

body.theme-dark {
    --bg-app: #0b0f19;
    --bg-sidebar: #0f172a;
    --bg-panel: #1e293b;
    --border-color: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #475569;
    
    --accent-color: #6366f1;
    --accent-color-hover: #818cf8;
    --accent-soft: rgba(99, 102, 241, 0.15);
    --accent-soft-hover: rgba(99, 102, 241, 0.25);
    
    --success-color: #34d399;
    --success-soft: rgba(52, 211, 153, 0.15);
    
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 8px 16px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 16px 32px rgba(0, 0, 0, 0.4);
    
    --card-bg: #1e293b;
    --card-bg-hover: #233146;
    
    --topic-selected-bg: #1e1b4b;
    --topic-selected-border: #4f46e5;
    
    --glass-bg: rgba(15, 23, 42, 0.8);
    --glass-border: rgba(51, 65, 85, 0.4);
    
    --scrollbar-thumb: #334155;
    --scrollbar-track: #0f172a;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Noto Serif Bengali', 'Outfit', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-app);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}
::-webkit-scrollbar-track {
    background: var(--scrollbar-track);
}
::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* App Container Layout */
.app-container {
    display: flex;
    width: 100vw;
    height: 100vh;
    overflow: hidden;
}

/* Left Sidebar Styles */
.sidebar-panel {
    width: 320px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
    z-index: 10;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.sidebar-header {
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
    transition: border-color 0.3s ease;
}

.logo-box {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    font-size: 26px;
    color: var(--accent-color);
    background: var(--accent-soft);
    padding: 10px;
    border-radius: 12px;
    transition: all 0.3s ease;
}

.logo-text {
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 2px;
    color: var(--text-primary);
}

.logo-subtitle {
    font-size: 11px;
    color: var(--text-muted);
    font-family: 'Outfit', sans-serif;
    letter-spacing: 0.5px;
    display: block;
}

/* Database Selector Custom Styles */
.sidebar-db-selector-box {
    padding: 16px 24px 8px 24px;
    border-bottom: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.db-select-label {
    font-size: 11px;
    font-weight: 600;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 6px;
    text-transform: uppercase;
    margin-bottom: 8px;
    letter-spacing: 0.5px;
}

.db-select-label i {
    color: var(--accent-color);
}

.db-select-wrapper {
    position: relative;
    width: 100%;
}

.custom-db-select {
    width: 100%;
    padding: 10px 14px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    color: var(--text-primary);
    font-size: 13px;
    font-weight: 600;
    outline: none;
    cursor: pointer;
    transition: all 0.3s ease;
}

.custom-db-select:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px var(--accent-soft);
    background-color: var(--bg-sidebar);
}

.sidebar-search-box {
    padding: 16px 24px;
    border-bottom: 1px solid var(--border-color);
}

.search-wrapper {
    position: relative;
    width: 100%;
}

.search-wrapper .search-icon {
    position: absolute;
    left: 14px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 14px;
    pointer-events: none;
    transition: color 0.3s ease;
}

.search-wrapper input {
    width: 100%;
    padding: 10px 14px 10px 38px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
    transition: all 0.3s ease;
}

.search-wrapper input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px var(--accent-soft);
    background-color: var(--bg-sidebar);
}

.sidebar-nav {
    flex-grow: 1;
    overflow-y: auto;
    padding: 16px 16px;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.sidebar-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px;
    gap: 12px;
    color: var(--text-secondary);
}

/* Sidebar Subject Item */
.subject-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 14px;
    border-radius: 14px;
    cursor: pointer;
    position: relative;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid transparent;
}

.subject-item:hover {
    background-color: var(--accent-soft);
    transform: translateY(-1px);
}

.subject-item.active {
    background-color: var(--accent-soft);
    border-color: var(--accent-soft-hover);
}

.subject-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 25%;
    height: 50%;
    width: 4px;
    background-color: var(--accent-color);
    border-radius: 0 4px 4px 0;
    transform: scaleX(0);
    transition: transform 0.25s ease;
}

.subject-item.active::before {
    transform: scaleX(1);
}

.subject-info {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-grow: 1;
    min-width: 0;
}

.subject-icon-box {
    width: 38px;
    height: 38px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
    flex-shrink: 0;
    transition: all 0.3s ease;
}

/* Subject Item Text */
.subject-text {
    display: flex;
    flex-direction: column;
    min-width: 0;
}

.subject-name-bengali {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.subject-name-english {
    font-size: 11px;
    color: var(--text-muted);
    font-family: 'Outfit', sans-serif;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.subject-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-right: 8px;
}

.subject-badge {
    background-color: var(--border-color);
    color: var(--text-secondary);
    font-size: 11px;
    font-weight: 600;
    padding: 3px 8px;
    border-radius: 20px;
    font-family: 'Outfit', sans-serif;
    transition: all 0.3s ease;
}

.subject-item.active .subject-badge {
    background-color: var(--accent-color);
    color: #ffffff;
}

/* Custom Checkbox Design */
.custom-checkbox {
    position: relative;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 20px;
    height: 20px;
    flex-shrink: 0;
}

.custom-checkbox input {
    opacity: 0;
    position: absolute;
    width: 100%;
    height: 100%;
    cursor: pointer;
    z-index: 2;
}

.checkbox-visual {
    width: 100%;
    height: 100%;
    border: 2px solid var(--text-muted);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 10px;
    color: transparent;
    background-color: transparent;
    transition: all 0.2s ease;
    z-index: 1;
}

.custom-checkbox input:checked + .checkbox-visual {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
    color: #ffffff;
}

.custom-checkbox input:indeterminate + .checkbox-visual {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
    color: #ffffff;
}

.custom-checkbox input:indeterminate + .checkbox-visual i::before {
    content: "\f068"; /* fa-minus */
}

.sidebar-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    font-size: 12px;
    color: var(--text-secondary);
}

.db-info {
    display: flex;
    align-items: center;
    gap: 8px;
    font-family: 'Outfit', sans-serif;
}

/* Main Area Styles */
.main-panel {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    height: 100%;
    position: relative;
}

/* Top Header Styles */
.top-header {
    height: 70px;
    background-color: var(--bg-sidebar);
    border-bottom: 1px solid var(--border-color);
    padding: 0 32px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-shrink: 0;
    transition: all 0.3s ease;
}

.global-search-wrapper {
    width: 360px;
}

.global-search-wrapper input {
    padding-right: 38px;
}

.clear-btn {
    position: absolute;
    right: 12px;
    top: 50%;
    transform: translateY(-50%);
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 14px;
    padding: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
}

.clear-btn:hover {
    color: var(--text-secondary);
    background-color: var(--border-color);
}

.header-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.global-stats-pill {
    background-color: var(--success-soft);
    color: var(--success-color);
    border: 1px solid rgba(16, 185, 129, 0.15);
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 13px;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 8px;
}

.theme-toggle-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 1px solid var(--border-color);
    background-color: var(--bg-sidebar);
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 16px;
    transition: all 0.3s ease;
}

.theme-toggle-btn:hover {
    background-color: var(--bg-app);
    color: var(--accent-color);
    border-color: var(--accent-color);
}

/* Content Container Scrollable */
.content-container {
    flex-grow: 1;
    overflow-y: auto;
    padding: 32px;
    padding-bottom: 110px; /* space for floating bottom action bar */
}

/* Empty State / Dashboard info */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    text-align: center;
    color: var(--text-secondary);
    padding: 60px 20px;
}

.empty-icon {
    font-size: 64px;
    color: var(--text-muted);
    margin-bottom: 24px;
    opacity: 0.7;
}

.empty-state h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.empty-state p {
    font-size: 14px;
    color: var(--text-muted);
    max-width: 400px;
}

/* Content Header / Subject Title box */
.detail-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    flex-wrap: wrap;
    gap: 16px;
}

.detail-title-box h2 {
    font-size: 22px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.detail-title-subtext {
    font-size: 13px;
    color: var(--text-muted);
}

.detail-actions {
    display: flex;
    gap: 10px;
}

.detail-actions .btn {
    font-size: 13px;
    font-weight: 500;
    padding: 8px 14px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    gap: 6px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-panel);
    color: var(--text-secondary);
    transition: all 0.2s ease;
}

.detail-actions .btn:hover {
    background-color: var(--bg-app);
    color: var(--text-primary);
}

.detail-actions .btn-primary {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
    color: #ffffff;
}

.detail-actions .btn-primary:hover {
    background-color: var(--accent-color-hover);
    border-color: var(--accent-color-hover);
    color: #ffffff;
}

/* Section Card (Depth 0 group container) */
.section-card {
    background-color: var(--bg-panel);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 24px;
    margin-bottom: 24px;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
}

.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 16px;
    margin-bottom: 16px;
}

.section-header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.section-icon {
    font-size: 18px;
    color: var(--accent-color);
    background: var(--accent-soft);
    padding: 8px;
    border-radius: 8px;
}

.section-title {
    font-size: 16px;
    font-weight: 700;
    color: var(--text-primary);
}

.section-badge {
    background-color: var(--border-color);
    color: var(--text-secondary);
    font-size: 12px;
    padding: 2px 8px;
    border-radius: 20px;
    font-family: 'Outfit', sans-serif;
}

.section-body {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

/* Grid layout for topics direct under a section */
.topics-direct-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 12px;
}

/* Chapter Accordion Card (Depth 1 group container) */
.chapter-card {
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    border-radius: 12px;
    overflow: hidden;
    transition: all 0.25s ease;
}

.chapter-card.expanded {
    box-shadow: var(--shadow-sm);
    border-color: var(--accent-soft-hover);
    background-color: var(--bg-panel);
}

.chapter-header {
    padding: 14px 18px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    cursor: pointer;
    user-select: none;
    transition: background-color 0.2s ease;
}

.chapter-header:hover {
    background-color: var(--accent-soft);
}

.chapter-header-left {
    display: flex;
    align-items: center;
    gap: 12px;
    min-width: 0;
}

.chapter-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.chapter-header-right {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-shrink: 0;
}

.chapter-badge {
    font-size: 11px;
    color: var(--text-secondary);
    background-color: var(--border-color);
    padding: 3px 8px;
    border-radius: 12px;
    font-family: 'Outfit', sans-serif;
}

.chapter-toggle-icon {
    color: var(--text-muted);
    font-size: 12px;
    transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.chapter-card.expanded .chapter-toggle-icon {
    transform: rotate(180deg);
}

.chapter-body {
    display: none;
    padding: 16px 18px;
    border-top: 1px solid var(--border-color);
    background-color: var(--bg-panel);
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 12px;
}

.chapter-card.expanded .chapter-body {
    display: grid;
}

/* Topic Card Style */
.topic-card {
    border: 1px solid var(--border-color);
    background-color: var(--bg-panel);
    border-radius: 10px;
    padding: 10px 14px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    transition: all 0.2s ease;
    min-width: 0;
    gap: 10px;
}

.topic-card:hover {
    border-color: var(--text-muted);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.topic-card.selected {
    background-color: var(--topic-selected-bg);
    border-color: var(--topic-selected-border);
}

.topic-left {
    display: flex;
    align-items: center;
    gap: 10px;
    min-width: 0;
    flex-grow: 1;
}

.topic-name {
    font-size: 13px;
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.topic-meta {
    display: flex;
    align-items: center;
    gap: 6px;
    flex-shrink: 0;
}

.topic-id-pill {
    background-color: var(--border-color);
    color: var(--text-secondary);
    font-size: 10px;
    font-weight: 600;
    padding: 2px 6px;
    border-radius: 6px;
    font-family: 'Outfit', sans-serif;
    letter-spacing: 0.2px;
}

.topic-card.selected .topic-id-pill {
    background-color: rgba(99, 102, 241, 0.12);
    color: var(--accent-color);
}

.copy-single-btn {
    border: none;
    background: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 12px;
    padding: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    transition: all 0.2s ease;
}

.copy-single-btn:hover {
    color: var(--accent-color);
    background-color: var(--accent-soft);
}

/* Text Highlighter for Search */
.highlight {
    background-color: #fef08a; /* soft yellow */
    color: #1e293b;
    padding: 0 2px;
    border-radius: 2px;
    font-weight: 600;
}

body.theme-dark .highlight {
    background-color: #854d0e; /* dark yellow-brown */
    color: #fef08a;
}

/* Floating bottom action bar */
.action-bar {
    position: fixed;
    bottom: 24px;
    left: calc(320px + (100vw - 320px - 800px) / 2); /* centered relative to main content */
    width: min(800px, calc(100vw - 320px - 48px));
    height: 76px;
    background-color: var(--glass-bg);
    border: 1px solid var(--border-color);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    z-index: 100;
    display: flex;
    align-items: center;
    padding: 0 24px;
    transform: translateY(150px);
    opacity: 0;
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.4s ease;
}

@media (max-width: 1200px) {
    .action-bar {
        left: calc(320px + 24px);
        width: calc(100vw - 320px - 48px);
    }
}

.action-bar.visible {
    transform: translateY(0);
    opacity: 1;
}

.action-bar-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.action-info {
    display: flex;
    align-items: center;
    gap: 14px;
}

.action-badge {
    background-color: var(--accent-color);
    color: #ffffff;
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 15px;
    font-family: 'Outfit', sans-serif;
    box-shadow: 0 4px 10px rgba(79, 70, 229, 0.3);
}

.action-text-box {
    display: flex;
    flex-direction: column;
}

.action-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--text-primary);
}

.action-subtext {
    font-size: 11px;
    color: var(--text-secondary);
}

.action-buttons {
    display: flex;
    gap: 8px;
}

.action-buttons .btn {
    font-size: 13px;
    font-weight: 600;
    padding: 8px 16px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    gap: 8px;
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-action-clear {
    background-color: var(--border-color);
    color: var(--text-secondary);
}

.btn-action-clear:hover {
    background-color: #f1f5f9;
    color: #ef4444;
}

body.theme-dark .btn-action-clear:hover {
    background-color: #ef444415;
    color: #f87171;
}

.btn-action-copy-csv {
    background-color: var(--accent-soft);
    color: var(--accent-color);
    border: 1px solid rgba(79, 70, 229, 0.15);
}

.btn-action-copy-csv:hover {
    background-color: var(--accent-color);
    color: #ffffff;
}

.btn-action-copy-json {
    background-color: var(--accent-color);
    color: #ffffff;
}

.btn-action-copy-json:hover {
    background-color: var(--accent-color-hover);
}

/* Toast System Styling */
.toast-container {
    position: fixed;
    top: 24px;
    right: 24px;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 8px;
    pointer-events: none;
}

.toast {
    pointer-events: auto;
    background-color: var(--bg-panel);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
    border-radius: 12px;
    padding: 12px 18px;
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--text-primary);
    font-size: 13px;
    font-weight: 500;
    animation: toast-in 0.35s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}

.toast i {
    color: var(--success-color);
    font-size: 16px;
}

@keyframes toast-in {
    from {
        transform: translateY(-20px) scale(0.9);
        opacity: 0;
    }
    to {
        transform: translateY(0) scale(1);
        opacity: 1;
    }
}

/* Fallback Loader Modal Window */
.modal-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(8px);
    z-index: 999;
    display: none; /* Controlled dynamically */
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal-backdrop.show {
    display: flex;
}

.custom-modal-card {
    background-color: var(--bg-sidebar);
    border: 1px solid var(--border-color);
    border-radius: 24px;
    width: 100%;
    max-width: 500px;
    box-shadow: var(--shadow-lg);
    padding: 32px;
    animation: modal-in 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

@keyframes modal-in {
    from {
        transform: translateY(30px) scale(0.95);
        opacity: 0;
    }
    to {
        transform: translateY(0) scale(1);
        opacity: 1;
    }
}

.modal-header-custom {
    text-align: center;
    margin-bottom: 24px;
}

.modal-icon {
    font-size: 44px;
    color: var(--accent-color);
    margin-bottom: 16px;
}

.modal-header-custom h3 {
    font-size: 20px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.modal-header-custom p {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.5;
}

.drag-drop-zone {
    border: 2px dashed var(--border-color);
    border-radius: 16px;
    padding: 32px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background-color: var(--bg-app);
}

.drag-drop-zone:hover, .drag-drop-zone.dragover {
    border-color: var(--accent-color);
    background-color: var(--accent-soft);
}

.upload-icon {
    font-size: 32px;
    color: var(--text-muted);
    margin-bottom: 12px;
    transition: all 0.3s ease;
}

.drag-drop-zone:hover .upload-icon {
    color: var(--accent-color);
    transform: translateY(-2px);
}

.drag-drop-zone h5 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 4px;
    color: var(--text-primary);
}

.drag-drop-zone span {
    font-size: 11px;
    color: var(--text-muted);
}

.or-divider {
    text-align: center;
    margin: 20px 0;
    position: relative;
}

.or-divider::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    width: 100%;
    height: 1px;
    background-color: var(--border-color);
    z-index: 1;
}

.or-divider span {
    background-color: var(--bg-sidebar);
    padding: 0 12px;
    font-size: 12px;
    color: var(--text-muted);
    position: relative;
    z-index: 2;
}

.url-input-box {
    display: flex;
    gap: 8px;
}

.url-input-box input {
    flex-grow: 1;
    padding: 10px 14px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    color: var(--text-primary);
    font-size: 13px;
    outline: none;
    transition: all 0.3s ease;
}

.url-input-box input:focus {
    border-color: var(--accent-color);
    background-color: var(--bg-sidebar);
}

.url-input-box button {
    border-radius: 12px;
    font-size: 13px;
    font-weight: 600;
    padding: 10px 18px;
}

/* --- Mobile Toggle Buttons (Hidden on Desktop) --- */
.sidebar-toggle-btn {
    display: none;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 1px solid var(--border-color);
    background-color: var(--bg-sidebar);
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 16px;
    transition: all 0.3s ease;
    flex-shrink: 0;
}

.sidebar-toggle-btn:hover {
    background-color: var(--bg-app);
    color: var(--accent-color);
    border-color: var(--accent-color);
}

.sidebar-close-btn {
    display: none;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: none;
    background-color: var(--border-color);
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 14px;
    transition: all 0.2s ease;
}

.sidebar-close-btn:hover {
    background-color: rgba(239, 68, 68, 0.1);
    color: #ef4444;
}

body.theme-dark .sidebar-close-btn:hover {
    background-color: rgba(248, 113, 113, 0.15);
    color: #f87171;
}

/* Sidebar Overlay (dims screen when sidebar is open on mobile) */
.sidebar-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    z-index: 999;
    display: none;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.sidebar-overlay.show {
    display: block;
    opacity: 1;
}

/* --- Responsive Media Queries --- */

/* Tablet & Mobile Screens */
@media (max-width: 991px) {
    .sidebar-panel {
        position: fixed;
        top: 0;
        left: -320px; /* Hidden offscreen by default */
        bottom: 0;
        width: 300px;
        height: 100%;
        z-index: 1000;
        transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        box-shadow: none;
    }

    .sidebar-panel.show {
        left: 0;
        box-shadow: var(--shadow-lg);
    }

    .sidebar-close-btn {
        display: flex;
    }

    .sidebar-header {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 16px 20px;
    }

    .sidebar-toggle-btn {
        display: flex;
    }

    .top-header {
        padding: 0 16px;
    }

    .global-search-wrapper {
        width: 100%;
        max-width: 280px;
    }

    .content-container {
        padding: 16px;
        padding-bottom: 120px; /* Extra spacing for floating action bar */
    }

    /* Floating bottom action bar mobile alignment */
    .action-bar {
        left: 12px;
        right: 12px;
        bottom: 12px;
        width: calc(100vw - 24px);
        height: auto;
        padding: 14px 18px;
        border-radius: 16px;
    }

    .action-bar-content {
        flex-direction: column;
        gap: 12px;
        align-items: stretch;
    }

    .action-info {
        justify-content: center;
        text-align: center;
    }

    .action-buttons {
        width: 100%;
        display: flex;
        gap: 8px;
    }

    .action-buttons .btn {
        flex: 1;
        justify-content: center;
        font-size: 12px;
        padding: 10px 8px;
    }
}

/* Smaller Tablets & Medium Mobile Screens */
@media (max-width: 768px) {
    /* Stack detail header elements */
    .detail-header {
        flex-direction: column;
        align-items: stretch;
        gap: 12px;
        text-align: left;
    }

    .detail-actions {
        width: 100%;
        display: flex;
        flex-wrap: wrap;
        gap: 8px;
    }

    .detail-actions .btn {
        flex: 1 1 calc(50% - 8px);
        justify-content: center;
        padding: 10px;
        font-size: 12px;
    }

    /* Grids scaling */
    .topics-direct-grid,
    .chapter-body {
        grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
        gap: 10px;
    }

    .section-card {
        padding: 16px;
    }
}

/* Small Mobile Screens */
@media (max-width: 576px) {
    .top-header {
        gap: 8px;
    }

    .global-search-wrapper {
        max-width: 160px; /* Shrink search wrapper to make space for stats & theme */
    }

    .global-search-wrapper input {
        padding: 8px 10px 8px 30px;
        font-size: 12px;
    }

    .global-search-wrapper .search-icon {
        left: 10px;
        font-size: 12px;
    }

    .global-stats-pill {
        padding: 6px 10px;
        font-size: 11px;
    }

    .global-stats-pill .stats-text {
        display: none; /* Hide 'মোট নির্বাচিত: ' text and show only check icon and count */
    }

    .theme-toggle-btn {
        width: 36px;
        height: 36px;
        font-size: 14px;
    }

    .sidebar-toggle-btn {
        width: 36px;
        height: 36px;
        font-size: 14px;
    }

    /* Grids scaling to single column */
    .topics-direct-grid,
    .chapter-body {
        grid-template-columns: 1fr;
    }

    /* Custom modal refinements */
    .custom-modal-card {
        padding: 20px;
        border-radius: 16px;
    }

    .url-input-box {
        flex-direction: column;
        gap: 8px;
    }

    .url-input-box button {
        width: 100%;
    }

    /* Action bar buttons wrapping on very small screens */
    .action-buttons {
        flex-wrap: wrap;
    }
    
    .btn-action-clear {
        order: 3; /* Push clear to the bottom/last */
        flex-basis: 100% !important;
    }
}