/* Import Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Playfair+Display:ital,wght@0,400;0,600;1,400&family=Space+Grotesk:wght@400;500;600;700&display=swap');

/* CSS Variables for Themes */
:root {
    --transition-speed: 0.3s;
    
    /* Dark Theme Variables (Default) */
    --bg-primary: #07090e;
    --bg-secondary: rgba(15, 22, 36, 0.85);
    --bg-tertiary: rgba(30, 41, 59, 0.7);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --accent-color: #06b6d4;
    --accent-hover: #22d3ee;
    --accent-glow: rgba(6, 182, 212, 0.15);
    --border-color: rgba(255, 255, 255, 0.08);
    --highlight-bg: rgba(234, 179, 8, 0.3);
    --highlight-text: #fef08a;
    --code-bg: #0f172a;
    --sidebar-width: 340px;
    --font-heading: 'Space Grotesk', sans-serif;
    --font-body: 'Inter', sans-serif;
    --card-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --glass-blur: blur(12px);
}

[data-theme="light"] {
    /* Light Theme Variables */
    --bg-primary: #f8fafc;
    --bg-secondary: rgba(255, 255, 255, 0.9);
    --bg-tertiary: rgba(241, 245, 249, 0.9);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --accent-color: #0891b2;
    --accent-hover: #0e7490;
    --accent-glow: rgba(8, 145, 178, 0.1);
    --border-color: rgba(0, 0, 0, 0.08);
    --highlight-bg: rgba(254, 240, 138, 0.7);
    --highlight-text: #854d0e;
    --code-bg: #e2e8f0;
    --card-shadow: 0 8px 32px 0 rgba(148, 163, 184, 0.15);
}

/* Font Families for Reading Pane */
.font-sans {
    font-family: 'Inter', sans-serif !important;
}
.font-serif {
    font-family: 'Playfair Display', Georgia, serif !important;
}
.font-tech {
    font-family: 'Space Grotesk', sans-serif !important;
}

/* Reset and Global Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-family: var(--font-body);
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    min-height: 100vh;
    overflow: hidden;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

/* App Layout */
.app-container {
    display: flex;
    width: 100%;
    height: 100vh;
    position: relative;
}

/* Reading Progress Bar */
.progress-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: transparent;
    z-index: 1000;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, var(--accent-color), var(--accent-hover));
    box-shadow: 0 0 8px var(--accent-color);
    transition: width 0.1s ease;
}

/* Sidebar Styling */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    height: 100%;
    z-index: 100;
    transition: transform var(--transition-speed), background-color var(--transition-speed), border-color var(--transition-speed), width var(--transition-speed);
}

/* Sidebar Brand & Header */
.sidebar-header {
    padding: 1.25rem 1.5rem 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 0.75rem;
}

.brand-icon {
    font-size: 1.5rem;
    color: var(--accent-color);
    filter: drop-shadow(0 0 6px var(--accent-glow));
}

.sidebar-title {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 700;
    letter-spacing: 0.02em;
    color: var(--text-primary);
}

/* Book Selector Dropdown Style */
.book-selector-container {
    position: relative;
    width: 100%;
    margin-bottom: 0.75rem;
    display: flex;
    align-items: center;
}

.book-select-icon {
    position: absolute;
    left: 0.8rem;
    color: var(--accent-color);
    font-size: 0.85rem;
    pointer-events: none;
}

.book-selector {
    width: 100%;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem 1rem 0.5rem 2.2rem;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 500;
    outline: none;
    cursor: pointer;
    transition: all 0.2s ease;
    appearance: none;
    background-image: url("data:image/svg+xml;utf8,<svg fill='%2306b6d4' height='24' viewBox='0 0 24 24' width='24' xmlns='http://www.w3.org/2000/svg'><path d='M7 10l5 5 5-5z'/><path d='M0 0h24v24H0z' fill='none'/></svg>");
    background-repeat: no-repeat;
    background-position: right 0.5rem center;
    background-size: 1.25rem;
}

.book-selector:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px var(--accent-glow);
}

.controls {
    display: flex;
    gap: 0.5rem;
    align-items: center;
    margin-bottom: 0.75rem;
    justify-content: space-between;
}

.btn-icon {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 36px;
    height: 36px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-icon:hover {
    background: var(--accent-color);
    color: #ffffff;
    border-color: var(--accent-color);
    box-shadow: 0 0 10px var(--accent-glow);
    transform: translateY(-2px);
}

/* Search Box style updates */
.search-box {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

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

.search-input {
    width: 100%;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem 1rem 0.5rem 2.2rem;
    border-radius: 8px;
    font-size: 0.85rem;
    outline: none;
    transition: all 0.2s ease;
}

.search-input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px var(--accent-glow);
}

.search-icon {
    position: absolute;
    left: 0.8rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
    font-size: 0.85rem;
    pointer-events: none;
}

.search-navigation {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    padding: 0.3rem 0.6rem;
    border-radius: 6px;
    font-size: 0.8rem;
}

.search-navigation button {
    background: transparent;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
}

.search-navigation button:hover {
    background: var(--accent-color);
    color: white;
}

/* Sidebar Tabs Navigation */
.sidebar-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.1);
}

.tab-btn {
    flex: 1;
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-secondary);
    padding: 0.75rem 0.25rem;
    font-size: 0.8rem;
    font-weight: 500;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.4rem;
    transition: all 0.2s ease;
}

.tab-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.02);
}

.tab-btn.active {
    color: var(--accent-color);
    border-bottom-color: var(--accent-color);
    background: rgba(6, 182, 212, 0.03);
}

/* Sidebar Tab Contents Pane */
.sidebar-content {
    flex: 1;
    overflow: hidden;
    position: relative;
}

.tab-pane {
    display: none;
    height: 100%;
    overflow-y: auto;
}

.tab-pane.active {
    display: block;
}

/* Sidebar Navigation Items */
.sidebar-nav {
    padding: 1rem 0;
}

.nav-item {
    display: block;
    padding: 0.5rem 1.25rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    line-height: 1.4;
    border-left: 2px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease;
}

.nav-item:hover {
    color: var(--text-primary);
    background-color: var(--bg-tertiary);
}

.nav-item.active {
    color: var(--accent-color);
    background-color: var(--accent-glow);
    border-left-color: var(--accent-color);
    font-weight: 600;
}

.nav-h1 { 
    font-family: var(--font-heading); 
    font-size: 1rem; 
    font-weight: 700; 
    text-transform: uppercase; 
    margin-top: 0.75rem; 
    padding-left: 1rem; 
    color: var(--text-primary); 
}
.nav-h2 { padding-left: 1.5rem; font-weight: 500; }
.nav-h3 { padding-left: 2rem; font-size: 0.8rem; }

/* Scientific Tools Tab Styling */
.tools-container, .highlights-container {
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.tool-card {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s, box-shadow 0.2s;
}

.tool-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--card-shadow);
}

.tool-card-header {
    background: rgba(0, 0, 0, 0.15);
    padding: 0.75rem 1rem;
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--accent-color);
    border-bottom: 1px solid var(--border-color);
}

.tool-card-body {
    padding: 1rem;
}

.tool-description {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    line-height: 1.4;
}

.form-group {
    margin-bottom: 0.75rem;
}

.form-group label {
    display: block;
    font-size: 0.75rem;
    margin-bottom: 0.25rem;
    color: var(--text-secondary);
}

.form-group input, .form-group select {
    width: 100%;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.4rem 0.6rem;
    border-radius: 6px;
    font-size: 0.8rem;
    outline: none;
}

.form-group input:focus, .form-group select:focus {
    border-color: var(--accent-color);
}

.btn-primary, .btn-secondary, .btn-success, .btn-danger {
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.3rem;
    width: 100%;
}

.btn-primary { background: var(--accent-color); color: #fff; }
.btn-primary:hover { background: var(--accent-hover); }

.btn-secondary { background: var(--bg-tertiary); color: var(--text-primary); border: 1px solid var(--border-color); }
.btn-secondary:hover { background: rgba(255,255,255,0.05); }

.btn-success { background: #10b981; color: #fff; }
.btn-success:hover { background: #059669; }

.btn-danger { background: #ef4444; color: #fff; }
.btn-danger:hover { background: #dc2626; }

.btn-sm { padding: 0.3rem 0.6rem; font-size: 0.75rem; }

.tool-result {
    margin-top: 0.75rem;
    padding: 0.75rem;
    background: var(--bg-primary);
    border-radius: 6px;
    border-left: 3px solid var(--accent-color);
    font-size: 0.75rem;
    line-height: 1.4;
    color: var(--text-primary);
    word-break: break-word;
}

/* Game Simulation stats & history */
.game-stats {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    font-weight: 600;
    background: var(--bg-primary);
    padding: 0.5rem;
    border-radius: 6px;
    margin-bottom: 0.75rem;
}

.game-controls {
    display: flex;
    gap: 0.5rem;
}

.game-history {
    margin-top: 0.75rem;
    max-height: 120px;
    overflow-y: auto;
    font-size: 0.7rem;
    background: var(--bg-primary);
    border-radius: 6px;
    padding: 0.5rem;
    color: var(--text-secondary);
}

.game-history-row {
    padding: 0.2rem 0;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
}

.game-history-row:last-child {
    border-bottom: none;
}

/* Saved Highlights list */
.section-title {
    font-family: var(--font-heading);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
}

.empty-message {
    font-size: 0.8rem;
    color: var(--text-secondary);
    text-align: center;
    margin-top: 2rem;
}

.highlight-item {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem;
    margin-bottom: 0.75rem;
    position: relative;
    transition: transform 0.2s;
}

.highlight-item:hover {
    transform: translateX(2px);
}

.highlight-item-text {
    font-size: 0.8rem;
    font-style: italic;
    color: var(--text-primary);
    line-height: 1.4;
    border-left: 2px solid var(--accent-color);
    padding-left: 0.5rem;
    margin-bottom: 0.5rem;
}

.highlight-item-note {
    font-size: 0.75rem;
    color: var(--text-secondary);
    background: var(--bg-primary);
    padding: 0.4rem;
    border-radius: 4px;
    margin-bottom: 0.5rem;
}

.highlight-item-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.7rem;
    color: var(--text-secondary);
}

.highlight-delete-btn {
    background: transparent;
    border: none;
    color: #ef4444;
    cursor: pointer;
}

/* Sidebar Footer */
.sidebar-footer {
    padding: 0.75rem 1.25rem;
    border-top: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.15);
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.reading-stat-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Main Reading Pane */
.reading-pane {
    flex: 1;
    height: 100%;
    overflow-y: auto;
    background-color: var(--bg-primary);
    padding: 5rem 2rem 3rem 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    transition: padding var(--transition-speed);
}

.reading-pane::-webkit-scrollbar {
    width: 8px;
}
.reading-pane::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

/* Floating Top Navigation */
.top-nav {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 56px;
    background: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    padding: 0 1.5rem;
    justify-content: space-between;
    z-index: 90;
    transition: background-color var(--transition-speed);
}

.btn-nav {
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.1rem;
    cursor: pointer;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    transition: background 0.2s;
}

.btn-nav:hover {
    background: var(--bg-tertiary);
}

.top-nav-title {
    font-family: var(--font-heading);
    font-size: 0.9rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    color: var(--accent-color);
    text-transform: uppercase;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 60%;
}

/* Content Container */
.content-container {
    max-width: 820px;
    width: 100%;
    line-height: 1.8;
    font-size: 1.05rem;
    font-weight: 400;
    color: var(--text-primary);
    transition: font-size 0.2s, line-height 0.2s, max-width 0.2s;
}

/* Typography elements */
.content-container h1, 
.content-container h2, 
.content-container h3, 
.content-container h4 {
    font-family: var(--font-heading);
    color: var(--text-primary);
    margin-top: 3rem;
    margin-bottom: 1.25rem;
    font-weight: 700;
    line-height: 1.3;
}

.content-container h1 {
    font-size: 2.4rem;
    border-bottom: 2px solid var(--accent-color);
    padding-bottom: 0.5rem;
    margin-top: 1.5rem;
    letter-spacing: -0.02em;
}

.content-container h2 {
    font-size: 1.7rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.3rem;
}

.content-container h3 {
    font-size: 1.3rem;
}

.content-container p {
    margin-bottom: 1.5rem;
}

.content-container strong {
    color: var(--accent-color);
    font-weight: 600;
}

.content-container ul, 
.content-container ol {
    margin-bottom: 1.5rem;
    padding-left: 1.75rem;
}

.content-container li {
    margin-bottom: 0.5rem;
}

/* Pre & Code */
.content-container pre {
    background-color: var(--code-bg);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 1.25rem;
    overflow-x: auto;
    margin-bottom: 1.5rem;
}

.content-container code {
    font-family: 'Consolas', 'Courier New', Courier, monospace;
    font-size: 0.85rem;
    background-color: var(--code-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    color: #f43f5e;
}

.content-container pre code {
    background-color: transparent;
    padding: 0;
    color: inherit;
}

/* Blockquotes */
.content-container blockquote {
    border-left: 4px solid var(--accent-color);
    background-color: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    padding: 1rem 1.5rem;
    margin: 1.75rem 0;
    border-radius: 0 10px 10px 0;
    font-style: italic;
    color: var(--text-secondary);
}

/* Tables */
.content-container table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
    font-size: 0.95rem;
}

.content-container th, 
.content-container td {
    border: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
    text-align: left;
}

.content-container th {
    background-color: rgba(0, 0, 0, 0.15);
    font-family: var(--font-heading);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--accent-color);
}

.content-container tr:nth-child(even) td {
    background-color: rgba(255, 255, 255, 0.02);
}

/* HR */
.content-container hr {
    border: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--border-color), transparent);
    margin: 3.5rem 0;
}

/* Search Highlighting */
mark {
    background-color: var(--highlight-bg);
    color: var(--highlight-text);
    border-radius: 3px;
    padding: 0 3px;
    box-shadow: 0 0 4px rgba(234, 179, 8, 0.3);
}

mark.current-match {
    background-color: #ef4444;
    color: white;
    box-shadow: 0 0 6px #ef4444;
}

/* Saved highlight marker in reading pane */
.text-highlight-yellow { background-color: rgba(234, 179, 8, 0.3); border-bottom: 2px dashed #eab308; }
.text-highlight-green { background-color: rgba(34, 197, 94, 0.3); border-bottom: 2px dashed #22c55e; }
.text-highlight-blue { background-color: rgba(59, 130, 246, 0.3); border-bottom: 2px dashed #3b82f6; }

/* Floating action buttons */
.floating-btn {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background-color: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 46px;
    height: 46px;
    border-radius: 50%;
    display: none;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.25);
    z-index: 85;
    transition: all 0.2s;
}

.floating-btn:hover {
    background-color: var(--accent-color);
    color: white;
    border-color: var(--accent-color);
    transform: translateY(-4px);
}

/* Settings Modal styling */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    z-index: 500;
    display: none;
    align-items: center;
    justify-content: center;
}

.modal-overlay.open {
    display: flex;
}

.modal {
    background: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    max-width: 480px;
    width: 90%;
    box-shadow: var(--card-shadow);
    overflow: hidden;
    animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
    from { transform: translateY(30px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.modal-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h3 {
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.close-btn {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
}

.close-btn:hover {
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
}

.setting-row {
    margin-bottom: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.setting-row:last-child {
    margin-bottom: 0;
}

.setting-row label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.btn-group {
    display: flex;
    background: var(--bg-primary);
    padding: 0.25rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.btn-choice {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 0.5rem 0.75rem;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-choice:hover {
    color: var(--text-primary);
}

.btn-choice.active {
    background: var(--accent-color);
    color: white;
}

.font-size-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

#font-size-display {
    font-size: 0.95rem;
    font-weight: 600;
    min-width: 50px;
    text-align: center;
}

/* Highlight menu popover */
.highlight-menu {
    position: absolute;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.4rem;
    display: flex;
    gap: 0.4rem;
    box-shadow: var(--card-shadow);
    z-index: 300;
}

.highlight-menu button {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    border: 1px solid rgba(255,255,255,0.2);
    cursor: pointer;
    transition: transform 0.1s;
}

.highlight-menu button:hover {
    transform: scale(1.15);
}

#btn-add-note {
    background: var(--bg-tertiary) !important;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    border-radius: 6px !important;
    width: 32px !important;
}

/* TTS Player Floating Bottom Panel */
.tts-player {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    background: var(--bg-secondary);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--border-color);
    padding: 0.75rem 1.5rem;
    border-radius: 30px;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    box-shadow: var(--card-shadow);
    z-index: 400;
    animation: slideUp 0.3s ease-out;
}

.tts-player-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.8rem;
    color: var(--text-primary);
}

.tts-controls {
    display: flex;
    align-items: center;
    gap: 0.6rem;
}

.btn-circle {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 34px;
    height: 34px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 0.8rem;
    transition: all 0.2s;
}

.btn-circle:hover {
    background: var(--accent-color);
    color: white;
    transform: scale(1.08);
}

.btn-circle.play {
    width: 40px;
    height: 40px;
    font-size: 0.95rem;
    background: var(--accent-color);
    color: white;
}
.btn-circle.play:hover {
    background: var(--accent-hover);
}

.btn-circle.stop:hover {
    background: #ef4444;
}

.tts-speed select, .tts-voice select {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.25rem 0.5rem;
    border-radius: 12px;
    font-size: 0.75rem;
    outline: none;
    max-width: 150px;
}

/* Zen Mode Styling */
body.zen-mode .sidebar {
    width: 0 !important;
    overflow: hidden;
    border-right: none;
    transform: translateX(-100%);
}

body.zen-mode .top-nav {
    left: 0;
    background: transparent;
    border-bottom: none;
    backdrop-filter: none;
}

body.zen-mode .top-nav-title {
    opacity: 0;
}

body.zen-mode .btn-nav {
    display: none;
}

body.zen-mode #zen-exit {
    display: flex;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 0.25rem 0.75rem;
    width: auto;
    font-size: 0.75rem;
}

body.zen-mode .reading-pane {
    padding-top: 3rem;
}

/* Mobile Toggle Menu */
.menu-toggle {
    display: none;
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    background-color: var(--accent-color);
    color: #ffffff;
    border: none;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    z-index: 99;
    transition: background-color 0.2s, transform 0.2s;
}

.menu-toggle:hover {
    background-color: var(--accent-hover);
    transform: scale(1.05);
}

/* Responsive adjustments */
@media (max-width: 992px) {
    body:not(.zen-mode) .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        bottom: 0;
        transform: translateX(-100%);
    }
    
    body:not(.zen-mode) .sidebar.open {
        transform: translateX(0);
    }
    
    body:not(.zen-mode) .menu-toggle {
        display: flex;
    }
    
    body:not(.zen-mode) .reading-pane {
        padding-top: 5rem;
    }
}

@media (max-width: 600px) {
    .tts-player {
        width: 95%;
        padding: 0.5rem 1rem;
        gap: 0.5rem;
        border-radius: 16px;
        bottom: 5rem;
    }
    
    .tts-player-info {
        display: none;
    }
    
    .tts-controls {
        flex: 1;
        justify-content: space-around;
    }
}