/* CSS Variables for easy theming */
:root {
    --bg-color: #f8f8f8;
    --text-color: #333;
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --border-color: #eee;
    --panel-bg: #fff;
    --panel-header-bg: #f0f0f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --font-content: 'Merriweather', serif;
    --font-ui: 'Open Sans', sans-serif;
    --font-size-base: 18px;
    --line-height-base: 1.8;
}

/* Night Mode Variables */
body.night-mode {
    --bg-color: #2c2c2c;
    --text-color: #e0e0e0;
    --primary-color: #8ab4f8;
    --secondary-color: #adb5bd;
    --border-color: #444;
    --panel-bg: #3a3a3a;
    --panel-header-bg: #4a4a4a;
    --shadow-color: rgba(0, 0, 0, 0.4);
}

/* Base Styles */
body {
    font-family: var(--font-ui);
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding-top: 60px; /* Space for fixed header */
    padding-bottom: 60px; /* Space for fixed bottom nav */
    transition: background-color 0.3s ease, color 0.3s ease;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 15px;
}

/* Header (Top Bar) */
.top-bar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: var(--panel-bg);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 2px 5px var(--shadow-color);
    z-index: 1000;
}

.top-bar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 60px;
}

.book-title-header {
    font-size: 1.2rem;
    font-weight: 600;
    margin: 0;
    flex-grow: 1;
    text-align: center;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 1.3rem;
    cursor: pointer;
    padding: 10px;
    transition: color 0.2s ease;
}

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

/* Main Content */
.main-content {
    padding: 20px 0;
}

.chapter-title {
    font-family: var(--font-content);
    font-size: 1.8rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 30px;
    color: var(--text-color);
}

.chapter-content {
    font-family: var(--font-content);
    font-size: var(--font-size-base);
    line-height: var(--line-height-base);
    color: var(--text-color);
    background-color: var(--panel-bg);
    padding: 25px;
    border-radius: 8px;
    box-shadow: 0 2px 10px var(--shadow-color);
}

.chapter-content p {
    margin-bottom: 1em;
    text-indent: 2em;
    text-align: justify;
}

/* No Select Class */
.no-select {
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

/* Navigation Bar (Bottom Bar) */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    background-color: var(--panel-bg);
    border-top: 1px solid var(--border-color);
    box-shadow: 0 -2px 5px var(--shadow-color);
    z-index: 1000;
}

.bottom-nav .container {
    display: flex;
    justify-content: space-around;
    align-items: center;
    height: 60px;
}

.nav-btn {
    background: none;
    border: none;
    color: var(--secondary-color);
    font-size: 0.9rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    cursor: pointer;
    padding: 5px 10px;
    transition: color 0.2s ease;
}

.nav-btn i {
    font-size: 1.3rem;
    margin-bottom: 5px;
}

.nav-btn span {
    white-space: nowrap;
}

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

/* Overlay */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.6);
    z-index: 1010;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.overlay.active {
    opacity: 1;
    visibility: visible;
}

/* Panels (Table of Contents & Settings) */
.panel {
    position: fixed;
    top: 0;
    right: -320px; /* Hidden by default */
    width: 300px;
    height: 100%;
    background-color: var(--panel-bg);
    box-shadow: -5px 0 15px var(--shadow-color);
    z-index: 1020;
    transition: right 0.3s ease;
    display: flex;
    flex-direction: column;
}

.panel.active {
    right: 0;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 20px;
    background-color: var(--panel-header-bg);
    border-bottom: 1px solid var(--border-color);
}

.panel-header h3 {
    margin: 0;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-color);
}

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

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

.panel-content {
    flex-grow: 1;
    padding: 20px;
    overflow-y: auto;
}

/* Table of Contents Specific */
.toc-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.toc-list li a {
    display: block;
    padding: 10px 0;
    color: var(--text-color);
    text-decoration: none;
    border-bottom: 1px solid var(--border-color);
    transition: background-color 0.2s ease;
}

.toc-list li a.active {
    color: var(--primary-color);
    font-weight: 600;
}

.toc-list li a:hover {
    background-color: var(--panel-header-bg);
    color: var(--primary-color);
}

/* Settings Panel Specific */
.setting-item {
    margin-bottom: 20px;
}

.setting-item label {
    display: block;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-color);
}

.setting-item input[type="range"] {
    width: 100%;
    -webkit-appearance: none;
    height: 8px;
    background: var(--border-color);
    border-radius: 5px;
    outline: none;
    opacity: 0.7;
    transition: opacity 0.2s;
}

.setting-item input[type="range"]:hover {
    opacity: 1;
}

.setting-item input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
}

.setting-item input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
}

.setting-item #fontSizeValue,
.setting-item #lineHeightValue {
    display: inline-block;
    margin-left: 10px;
    font-weight: 600;
    color: var(--primary-color);
}

.setting-item select {
    width: 100%;
    padding: 8px 10px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--panel-bg);
    color: var(--text-color);
    appearance: none; /* Remove default arrow */
    -webkit-appearance: none;
    -moz-appearance: none;
    background-image: url('data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%22292.4%22%20height%3D%22292.4%22%3E%3Cpath%20fill%3D%22%23007bff%22%20d%3D%22M287%2069.4a17.6%2017.6%200%200%200-13-5.4H18.4c-6.5%200-12.3%203.2-16.1%208.1-3.8%204.9-4.9%2011-3.1%2016.9l132.6%20132.3c3.8%203.8%209%205.9%2014.3%205.9s10.5-2.1%2014.3-5.9L287%2086.3c3.8-3.8%205.9-9%205.9-14.3s-2.1-10.5-5.9-14.3z%22%2F%3E%3C%2Fsvg%3E');
    background-repeat: no-repeat;
    background-position: right 10px center;
    background-size: 12px;
}

body.night-mode .setting-item select {
    background-image: url('data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%22292.4%22%20height%3D%22292.4%22%3E%3Cpath%20fill%3D%22%238ab4f8%22%20d%3D%22M287%2069.4a17.6%2017.6%200%200%200-13-5.4H18.4c-6.5%200-12.3%203.2-16.1%208.1-3.8%204.9-4.9%2011-3.1%2016.9l132.6%20132.3c3.8%203.8%209%205.9%2014.3%205.9s10.5-2.1%2014.3-5.9L287%2086.3c3.8-3.8%205.9-9%205.9-14.3s-2.1-10.5-5.9-14.3z%22%2F%3E%3C%2Fsvg%3E');
}

/* Toggle Switch (for Theme) */
.switch {
    position: relative;
    display: inline-block;
    width: 40px;
    height: 24px;
    vertical-align: middle;
    margin-left: 10px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--secondary-color);
    transition: .4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    transition: .4s;
}

input:checked + .slider {
    background-color: var(--primary-color);
}

input:focus + .slider {
    box-shadow: 0 0 1px var(--primary-color);
}

input:checked + .slider:before {
    transform: translateX(16px);
}

/* Rounded sliders */
.slider.round {
    border-radius: 24px;
}

.slider.round:before {
    border-radius: 50%;
}

/* Responsive Adjustments */
@media (max-width: 768px) {
    .chapter-title {
        font-size: 1.5rem;
    }
    .chapter-content {
        padding: 15px;
    }
    .panel {
        width: 100%; /* Full width on small screens */
        right: -100%;
    }
    .panel.active {
        right: 0;
    }
}
/* Thêm vào cuối file style.css */
.top-bar.hidden {
    transform: translateY(-100%);
    transition: transform 0.3s ease-in-out;
}

.bottom-nav.hidden {
    transform: translateY(100%);
    transition: transform 0.3s ease-in-out;
}

/* Đảm bảo trạng thái ban đầu */
.top-bar, .bottom-nav {
    transition: transform 0.3s ease-in-out;
}