:root {
    --bg-color: #0f0f11;
    --bg-surface: #18181b;
    --bg-elevated: #1e1e22;
    --bg-hover: #27272a;
    --text-primary: #fafafa;
    --text-secondary: #a1a1aa;
    --text-muted: #71717a;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --accent-glow: rgba(99, 102, 241, 0.25);
    --orp-color: #e53e3e;
    --orp-glow: rgba(229, 62, 62, 0.3);
    --border: rgba(255, 255, 255, 0.06);
    --border-strong: rgba(255, 255, 255, 0.1);
    --guide-line: rgba(255, 255, 255, 0.04);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --font-ui: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition: 200ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* Light mode overrides */
:root.light {
    --bg-color: #ffffff;
    --bg-surface: #f4f4f5;
    --bg-elevated: #e4e4e7;
    --bg-hover: #d4d4d8;
    --text-primary: #09090b;
    --text-secondary: #52525b;
    --text-muted: #a1a1aa;
    --accent: #4f46e5;
    --accent-hover: #6366f1;
    --accent-glow: rgba(79, 70, 229, 0.2);
    --orp-color: #dc2626;
    --orp-glow: rgba(220, 38, 38, 0.25);
    --border: rgba(0, 0, 0, 0.08);
    --border-strong: rgba(0, 0, 0, 0.15);
    --guide-line: rgba(0, 0, 0, 0.06);
}

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

body {
    font-family: var(--font-ui);
    background-color: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    display: flex;
    flex-direction: column;
    height: 100%;
}

/* ========== Toolbar ========== */
.toolbar {
    background: var(--bg-surface);
    padding: 0 1.25rem;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
}

.toolbar-left,
.toolbar-right {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.app-title {
    font-size: 1.05rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    user-select: none;
}

.logo-icon {
    color: var(--accent);
}

.btn-ghost {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

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

.file-controls {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

#fileInput {
    display: none;
}

.btn {
    padding: 0.45rem 1rem;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    font-family: var(--font-ui);
    font-weight: 500;
    font-size: 0.8rem;
    transition: all var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

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

.btn-primary:hover {
    background: var(--accent-hover);
    box-shadow: 0 0 20px var(--accent-glow);
}

.file-name {
    color: var(--text-muted);
    font-size: 0.8rem;
    max-width: 300px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* ========== Workspace ========== */
.workspace {
    display: flex;
    flex: 1;
    overflow: hidden;
}

/* ========== Sidebar ========== */
.sidebar {
    width: 240px;
    background: var(--bg-surface);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    transition: width var(--transition), opacity var(--transition);
    overflow: hidden;
    flex-shrink: 0;
}

.sidebar.collapsed {
    width: 0;
    border-right: none;
    opacity: 0;
    pointer-events: none;
}

.sidebar-header {
    padding: 1rem 1rem 0.5rem;
}

.sidebar-header h2 {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.chapter-list {
    list-style: none;
    overflow-y: auto;
    flex: 1;
    padding: 0.25rem 0.5rem 0.5rem;
}

.chapter-list::-webkit-scrollbar {
    width: 4px;
}

.chapter-list::-webkit-scrollbar-track {
    background: transparent;
}

.chapter-list::-webkit-scrollbar-thumb {
    background: var(--bg-hover);
    border-radius: 4px;
}

.chapter-list li {
    padding: 0.45rem 0.6rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.82rem;
    transition: all var(--transition);
    margin-bottom: 1px;
}

.chapter-list li:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.chapter-list li.active {
    background: var(--accent-glow);
    color: var(--accent-hover);
}

.chapter-list li.empty-state {
    color: var(--text-muted);
    cursor: default;
    font-size: 0.78rem;
    padding: 1rem 0.6rem;
    text-align: center;
}

.chapter-list li.empty-state:hover {
    background: transparent;
    color: var(--text-muted);
}

/* ========== Reading Area ========== */
.reading-area {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    background: var(--bg-color);
    position: relative;
    overflow: hidden;
}

/* Subtle radial glow behind reading focus */
.reading-area::before {
    content: '';
    position: absolute;
    width: 500px;
    height: 300px;
    background: radial-gradient(ellipse, var(--accent-glow) 0%, transparent 70%);
    opacity: 0.15;
    pointer-events: none;
}

.canvas-container {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1;
}

/* ========== Drop Zone ========== */
.drop-zone {
    position: absolute;
    inset: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 5;
    transition: opacity var(--transition);
}

.drop-zone.hidden {
    opacity: 0;
    pointer-events: none;
}

.drop-zone-content {
    text-align: center;
    color: var(--text-muted);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.drop-image {
    max-width: 480px;
    max-height: 60vh;
    object-fit: contain;
    border-radius: var(--radius-md);
    margin-bottom: 0.5rem;
}

.drop-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.drop-subtitle {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.drop-subtitle strong {
    color: var(--accent-hover);
}

.supported-formats {
    display: flex;
    gap: 0.4rem;
    margin-top: 0.5rem;
}

.format-tag {
    font-size: 0.65rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    padding: 0.2rem 0.55rem;
    border-radius: 99px;
    border: 1px solid var(--border-strong);
    color: var(--text-muted);
}

/* Drag-active state */
.drop-zone.drag-over .drop-zone-content {
    color: var(--accent-hover);
}

.drop-zone.drag-over .drop-zone-content svg {
    color: var(--accent);
    opacity: 1;
}

.drop-zone.drag-over .drop-title {
    color: var(--accent-hover);
}

.drop-zone.drag-over .format-tag {
    border-color: var(--accent);
    color: var(--accent-hover);
}

/* ========== Controls ========== */
.controls {
    background: var(--bg-surface);
    padding: 0 1.25rem;
    height: 64px;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    border-top: 1px solid var(--border);
    flex-shrink: 0;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

/* Play Button */
.btn-play {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: none;
    background: var(--accent);
    color: white;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
    flex-shrink: 0;
}

.btn-play:hover {
    background: var(--accent-hover);
    box-shadow: 0 0 24px var(--accent-glow);
    transform: scale(1.06);
}

.btn-play:active {
    transform: scale(0.96);
}

/* Settings */
.settings {
    display: flex;
    gap: 1.5rem;
}

.setting-item {
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
}

.setting-item label {
    font-size: 0.65rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.slider-row {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.slider-value {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
    min-width: 2rem;
    text-align: right;
}

/* Progress */
.progress {
    flex: 1;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

#progressSlider {
    width: 100%;
}

.progress-text {
    font-size: 0.78rem;
    font-weight: 500;
    font-variant-numeric: tabular-nums;
    color: var(--text-secondary);
    min-width: 3rem;
    text-align: right;
}

/* ========== Custom Range Sliders ========== */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 130px;
    height: 4px;
    background: var(--bg-hover);
    border-radius: 99px;
    outline: none;
    cursor: pointer;
    transition: background var(--transition);
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--bg-surface);
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: 0 0 0 0 var(--accent-glow);
}

input[type="range"]::-webkit-slider-thumb:hover {
    background: var(--accent-hover);
    box-shadow: 0 0 10px var(--accent-glow);
    transform: scale(1.2);
}

input[type="range"]::-moz-range-thumb {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--bg-surface);
    cursor: pointer;
    transition: all var(--transition);
}

input[type="range"]::-moz-range-thumb:hover {
    background: var(--accent-hover);
}

input[type="range"]::-moz-range-track {
    height: 4px;
    background: var(--bg-hover);
    border-radius: 99px;
}

/* ========== Animations ========== */
@keyframes fade-in {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

.drop-zone-content {
    animation: fade-in 0.5s ease-out;
}