/**
 * Design System - Minimalist Black/White Theme
 * 极简黑白设计系统
 *
 * Features:
 * - Minimalist neutral palette with modern blue accent
 * - Complete dark mode support
 * - 8px spacing grid
 * - Unified component library
 * - Mobile-first responsive design
 */

/* ========================================
   CSS VARIABLES - LIGHT MODE
   ======================================== */

:root {
  /* === Colors - Minimalist Black/White === */

  /* White & Light Grays */
  --color-white: #FFFFFF;
  --color-gray-50: #FAFAFA;
  --color-gray-100: #F5F5F5;
  --color-gray-200: #EEEEEE;
  --color-gray-300: #E0E0E0;

  /* Mid Grays */
  --color-gray-400: #BDBDBD;
  --color-gray-500: #999999;
  --color-gray-600: #757575;
  --color-gray-700: #616161;

  /* Dark Grays & Black */
  --color-gray-800: #424242;
  --color-gray-900: #212121;
  --color-black: #000000;

  /* Accent Colors */
  --color-primary: #0F6CFF;
  --color-primary-rgb: 15, 108, 255;
  --color-primary-light: #5BC6FF;
  --color-primary-dark: #003FAE;
  --color-primary-bg: rgba(15, 108, 255, 0.16);

  /* Secondary Accents */
  --color-accent-purple: #00C2FF;
  --color-accent-indigo: #1A56F0;

  /* Gradients */
  --gradient-primary: linear-gradient(138deg, #071A49 0%, var(--color-primary) 58%, var(--color-accent-purple) 100%);
  --gradient-accent: linear-gradient(135deg, #0A2E85 0%, var(--color-accent-indigo) 46%, var(--color-accent-purple) 100%);
  --gradient-primary-horizontal: linear-gradient(90deg, var(--color-primary), var(--color-accent-purple));

  /* Semantic Colors */
  --color-success: #34C759;
  --color-success-bg: rgba(52, 199, 89, 0.1);
  --color-success-dark: #2E7D32;
  --color-warning: #FF9500;
  --color-warning-bg: rgba(255, 149, 0, 0.1);
  --color-error: #FF3B30;
  --color-error-bg: rgba(255, 59, 48, 0.1);
  --color-error-dark: #D32F2F;
  --color-info: #28C7FF;
  --color-info-bg: rgba(40, 199, 255, 0.12);

  /* Alert Text Colors */
  --color-alert-success-text: #1B5E20;
  --color-alert-warning-text: #E65100;
  --color-alert-error-text: #C62828;
  --color-alert-info-text: #0277BD;
  --color-alert-caution-text: #856404;

  /* Download Button Colors */
  --color-download-md: #3498db;
  --color-download-epub: #0ea5e9;
  --color-download-danger: #e74c3c;

  /* === Backgrounds === */
  --bg-primary: var(--color-white);
  --bg-secondary: var(--color-gray-50);
  --bg-tertiary: var(--color-gray-100);
  --bg-elevated: var(--color-white);
  --bg-overlay: rgba(0, 0, 0, 0.5);
  --bg-backdrop: rgba(255, 255, 255, 0.8);
  --bg-base: var(--bg-secondary);
  --bg-surface: var(--bg-elevated);
  --bg-surface-muted: var(--bg-tertiary);

  /* === Text Colors === */
  --text-primary: var(--color-gray-900);
  --text-secondary: var(--color-gray-600);
  --text-tertiary: var(--color-gray-500);
  --text-disabled: var(--color-gray-400);
  --text-inverse: var(--color-white);
  --text-link: var(--color-primary);
  --text-muted: var(--text-tertiary);

  /* === Border Colors === */
  --border-color: var(--color-gray-300);
  --border-color-light: var(--color-gray-200);
  --border-color-dark: var(--color-gray-400);
  --border-color-focus: var(--color-primary);
  --color-secondary-bg: var(--bg-tertiary);
  --color-disabled: var(--color-gray-300);
  --focus-ring: 0 0 0 3px var(--color-primary-bg);

  /* === Typography === */
  --font-family-base: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  --font-family-heading: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  --font-family-mono: "SF Mono", Consolas, "Liberation Mono", Menlo, monospace;

  /* Font Sizes - 8px grid */
  --font-size-xs: 0.75rem;      /* 12px */
  --font-size-sm: 0.875rem;     /* 14px */
  --font-size-base: 1rem;       /* 16px */
  --font-size-lg: 1.125rem;     /* 18px */
  --font-size-xl: 1.25rem;      /* 20px */
  --font-size-2xl: 1.5rem;      /* 24px */
  --font-size-3xl: 1.875rem;    /* 30px */
  --font-size-4xl: 2.25rem;     /* 36px */
  --font-size-5xl: 3rem;        /* 48px */

  /* Font Weights */
  --font-weight-light: 300;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  /* Line Heights */
  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.75;
  --line-height-loose: 2;

  /* === Spacing - 8px Grid === */
  --spacing-0: 0;
  --spacing-1: 0.25rem;  /* 4px */
  --spacing-2: 0.5rem;   /* 8px */
  --spacing-3: 0.75rem;  /* 12px */
  --spacing-4: 1rem;     /* 16px */
  --spacing-5: 1.25rem;  /* 20px */
  --spacing-6: 1.5rem;   /* 24px */
  --spacing-8: 2rem;     /* 32px */
  --spacing-10: 2.5rem;  /* 40px */
  --spacing-12: 3rem;    /* 48px */
  --spacing-16: 4rem;    /* 64px */
  --spacing-20: 5rem;    /* 80px */

  /* === Border Radius === */
  --radius-xs: 4px;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-2xl: 24px;
  --radius-full: 9999px;

  /* === Shadows === */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07), 0 2px 4px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1), 0 4px 6px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.1), 0 10px 10px rgba(0, 0, 0, 0.04);
  --shadow-2xl: 0 25px 50px rgba(0, 0, 0, 0.15);

  /* Shadow with color */
  --shadow-primary: 0 4px 14px rgba(15, 108, 255, 0.32);
  --shadow-success: 0 4px 14px rgba(52, 199, 89, 0.3);
  --shadow-error: 0 4px 14px rgba(255, 59, 48, 0.3);

  /* === Transitions === */
  --transition-fast: 150ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;
  --transition-slower: 500ms ease;

  /* === Z-Index === */
  --z-base: 1;
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-fixed: 300;
  --z-modal-backdrop: 400;
  --z-modal: 500;
  --z-popover: 600;
  --z-tooltip: 700;

  /* === Layout === */
  --max-width-xs: 480px;
  --max-width-sm: 640px;
  --max-width-md: 768px;
  --max-width-lg: 1024px;
  --max-width-xl: 1280px;
  --max-width-2xl: 1536px;
  --container-max-width: 1200px;
  --container-max-width-wide: 1440px;
  --container-padding-inline: clamp(12px, 3vw, 32px);
  --touch-target-min: 44px;
  --content-max-readable: 78ch;

  /* === Breakpoints (for reference in JS) === */
  --breakpoint-sm: 640px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 1024px;
  --breakpoint-xl: 1280px;
}

/* ========================================
   CSS VARIABLES - DARK MODE
   ======================================== */

@media (prefers-color-scheme: dark) {
  :root {
    /* === Colors - Dark Mode (OpenClaw-inspired) === */
    --color-primary: #FF5A2D;
    --color-primary-rgb: 255, 90, 45;
    --color-primary-light: #FF8A67;
    --color-primary-dark: #CF3F1B;
    --color-accent-purple: #4E6FA1;
    --color-accent-indigo: #2F5F99;
    --gradient-primary: linear-gradient(138deg, #0D1117 0%, #132033 58%, #1D3552 100%);
    --gradient-accent: linear-gradient(135deg, #162334 0%, #28405E 54%, #FF5A2D 100%);
    --gradient-primary-horizontal: linear-gradient(90deg, #FF5A2D, #4E6FA1);

    /* Backgrounds */
    --bg-primary: #0D1117;
    --bg-secondary: #111926;
    --bg-tertiary: #162233;
    --bg-elevated: #171F2B;
    --bg-overlay: rgba(0, 0, 0, 0.7);
    --bg-backdrop: rgba(13, 17, 23, 0.82);
    --bg-base: var(--bg-secondary);
    --bg-surface: var(--bg-elevated);
    --bg-surface-muted: var(--bg-tertiary);

    /* Text Colors */
    --text-primary: #F3F6FB;
    --text-secondary: #A2ADBC;
    --text-tertiary: #7F8CA0;
    --text-disabled: #5C6A80;
    --text-inverse: var(--color-gray-900);
    --text-muted: var(--text-tertiary);

    /* Border Colors */
    --border-color: #2A3546;
    --border-color-light: #243142;
    --border-color-dark: #3A4C63;
    --color-secondary-bg: rgba(255, 255, 255, 0.08);
    --color-disabled: #2A3546;

    /* Semantic Backgrounds */
    --color-primary-bg: rgba(255, 90, 45, 0.2);
    --color-success-bg: rgba(52, 199, 89, 0.18);
    --color-warning-bg: rgba(255, 149, 0, 0.18);
    --color-error-bg: rgba(255, 59, 48, 0.18);
    --color-info-bg: rgba(78, 111, 161, 0.2);
    --shadow-primary: 0 6px 18px rgba(255, 90, 45, 0.34);

    /* Alert Text Colors - Dark Mode */
    --color-alert-success-text: #4CAF50;
    --color-alert-warning-text: #FFB74D;
    --color-alert-error-text: #EF5350;
    --color-alert-info-text: #4FC3F7;
    --color-alert-caution-text: #FFD54F;
  }
}

/* Manual dark mode toggle class */
.dark {
  --color-primary: #FF5A2D;
  --color-primary-rgb: 255, 90, 45;
  --color-primary-light: #FF8A67;
  --color-primary-dark: #CF3F1B;
  --color-accent-purple: #4E6FA1;
  --color-accent-indigo: #2F5F99;
  --gradient-primary: linear-gradient(138deg, #0D1117 0%, #132033 58%, #1D3552 100%);
  --gradient-accent: linear-gradient(135deg, #162334 0%, #28405E 54%, #FF5A2D 100%);
  --gradient-primary-horizontal: linear-gradient(90deg, #FF5A2D, #4E6FA1);

  --bg-primary: #0D1117;
  --bg-secondary: #111926;
  --bg-tertiary: #162233;
  --bg-elevated: #171F2B;
  --bg-overlay: rgba(0, 0, 0, 0.7);
  --bg-backdrop: rgba(13, 17, 23, 0.82);
  --bg-base: var(--bg-secondary);
  --bg-surface: var(--bg-elevated);
  --bg-surface-muted: var(--bg-tertiary);

  --text-primary: #F3F6FB;
  --text-secondary: #A2ADBC;
  --text-tertiary: #7F8CA0;
  --text-disabled: #5C6A80;
  --text-inverse: var(--color-gray-900);
  --text-muted: var(--text-tertiary);

  --border-color: #2A3546;
  --border-color-light: #243142;
  --border-color-dark: #3A4C63;
  --color-secondary-bg: rgba(255, 255, 255, 0.08);
  --color-disabled: #2A3546;
  --focus-ring: 0 0 0 3px rgba(255, 90, 45, 0.28);

  --color-primary-bg: rgba(255, 90, 45, 0.2);
  --color-success-bg: rgba(52, 199, 89, 0.18);
  --color-warning-bg: rgba(255, 149, 0, 0.18);
  --color-error-bg: rgba(255, 59, 48, 0.18);
  --color-info-bg: rgba(78, 111, 161, 0.2);
  --shadow-primary: 0 6px 18px rgba(255, 90, 45, 0.34);

  /* Alert Text Colors - Dark Mode */
  --color-alert-success-text: #4CAF50;
  --color-alert-warning-text: #FFB74D;
  --color-alert-error-text: #EF5350;
  --color-alert-info-text: #4FC3F7;
  --color-alert-caution-text: #FFD54F;
}

/* ========================================
   BASE STYLES
   ======================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  margin: 0;
  padding: 0;
  min-height: 100vh;
  overflow-wrap: break-word;
}

.container {
  width: min(100% - (var(--container-padding-inline) * 2), var(--container-max-width));
  margin-inline: auto;
}

.container-wide {
  width: min(100% - (var(--container-padding-inline) * 2), var(--container-max-width-wide));
  margin-inline: auto;
}

:focus-visible {
  outline: 2px solid var(--border-color-focus);
  outline-offset: 2px;
}

button,
input[type="button"],
input[type="submit"],
input[type="reset"],
.btn,
.bottom-nav-item,
.nav-link {
  min-height: var(--touch-target-min);
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Headings */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-family-heading);
  font-weight: var(--font-weight-semibold);
  line-height: var(--line-height-tight);
  margin: 0 0 var(--spacing-4) 0;
  color: var(--text-primary);
}

h1 { font-size: var(--font-size-5xl); }
h2 { font-size: var(--font-size-4xl); }
h3 { font-size: var(--font-size-3xl); }
h4 { font-size: var(--font-size-2xl); }
h5 { font-size: var(--font-size-xl); }
h6 { font-size: var(--font-size-lg); }

/* Paragraphs */
p {
  margin: 0 0 var(--spacing-4) 0;
}

/* Links */
a {
  color: var(--text-link);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary-dark);
  text-decoration: underline;
}

/* Lists */
ul, ol {
  margin: 0 0 var(--spacing-4) 0;
  padding-left: var(--spacing-6);
}

/* Images */
img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* Horizontal Rule */
hr {
  border: none;
  border-top: 1px solid var(--border-color);
  margin: var(--spacing-8) 0;
}

/* Code */
code, pre {
  font-family: var(--font-family-mono);
}

code {
  background-color: var(--bg-tertiary);
  padding: var(--spacing-1) var(--spacing-2);
  border-radius: var(--radius-xs);
  font-size: 0.9em;
}

pre {
  background-color: var(--bg-tertiary);
  padding: var(--spacing-4);
  border-radius: var(--radius-sm);
  overflow-x: auto;
  line-height: var(--line-height-relaxed);
}

pre code {
  background-color: transparent;
  padding: 0;
}

/* ========================================
   BUTTONS
   ======================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-2);
  padding: var(--spacing-3) var(--spacing-6);
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  line-height: 1;
  border: 1px solid transparent;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition:
    transform var(--transition-fast),
    box-shadow var(--transition-base),
    border-color var(--transition-base),
    background-color var(--transition-base),
    color var(--transition-base);
  text-decoration: none;
  white-space: nowrap;
  user-select: none;
  min-height: var(--touch-target-min);
  box-shadow: var(--shadow-xs);
}

.btn:focus-visible {
  outline: none;
  box-shadow: var(--shadow-xs), var(--focus-ring);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
  transform: none;
  box-shadow: none;
}

.btn:active:not(:disabled) {
  transform: translateY(0);
}

/* Button Variants */
.btn-primary {
  background: linear-gradient(180deg, var(--color-primary-light) 0%, var(--color-primary) 100%);
  border-color: var(--color-primary);
  color: var(--color-white);
}

.btn-primary:hover:not(:disabled) {
  background: linear-gradient(180deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  transform: translateY(-1px);
  box-shadow: var(--shadow-primary);
}

.btn-secondary {
  background-color: var(--bg-elevated);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--bg-secondary);
  border-color: var(--border-color-dark);
}

.btn-ghost {
  background-color: transparent;
  color: var(--text-primary);
  border-color: transparent;
}

.btn-ghost:hover:not(:disabled) {
  background-color: var(--bg-tertiary);
}

.btn-danger {
  background: linear-gradient(180deg, #ff6b63 0%, var(--color-error) 100%);
  border-color: var(--color-error);
  color: var(--color-white);
}

.btn-danger:hover:not(:disabled) {
  background-color: var(--color-error-dark);
  box-shadow: var(--shadow-error);
}

.btn-success {
  background: linear-gradient(180deg, #4edb7d 0%, var(--color-success) 100%);
  border-color: var(--color-success);
  color: var(--color-white);
}

.btn-success:hover:not(:disabled) {
  background-color: var(--color-success-dark);
  box-shadow: var(--shadow-success);
}

/* Button Sizes */
.btn-sm {
  padding: var(--spacing-2) var(--spacing-4);
  font-size: var(--font-size-sm);
  min-height: var(--touch-target-min);
}

.btn-lg {
  padding: var(--spacing-4) var(--spacing-8);
  font-size: var(--font-size-lg);
  min-height: 52px;
}

/* Button Icon Only */
.btn-icon {
  padding: var(--spacing-3);
  aspect-ratio: 1;
}

/* ========================================
   CARDS
   ======================================== */

.card {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: clamp(var(--spacing-4), 2vw, var(--spacing-6));
  box-shadow: var(--shadow-sm);
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base),
    border-color var(--transition-base);
}

.card-elevated {
  box-shadow: var(--shadow-md);
}

.card-elevated:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
  border-color: var(--border-color-dark);
}

.card-compact {
  padding: var(--spacing-4);
}

.card-spacious {
  padding: var(--spacing-8);
}

/* Book Card */
.book-card {
  position: relative;
  overflow: hidden;
}

.book-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-primary-light));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.book-card:hover::before {
  opacity: 1;
}

.book-cover {
  aspect-ratio: 3/4;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--font-size-5xl);
  color: var(--color-white);
  margin-bottom: var(--spacing-4);
}

/* ========================================
   FORMS
   ======================================== */

.form-group {
  margin-bottom: var(--spacing-4);
}

.form-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--spacing-1) var(--spacing-3);
  margin-bottom: var(--spacing-2);
}

.form-label {
  font-weight: var(--font-weight-medium);
  color: var(--text-primary);
  font-size: var(--font-size-sm);
  white-space: nowrap;
  flex-shrink: 0;
}

.form-label .required {
  color: var(--color-error);
  margin-left: 2px;
}

.form-help {
  font-size: var(--font-size-xs);
  color: var(--text-tertiary);
  white-space: normal;
  overflow: visible;
  text-overflow: clip;
  line-height: 1.4;
}

.form-error {
  font-size: var(--font-size-sm);
  color: var(--color-error);
  margin-top: var(--spacing-1);
  display: none;
}

.form-error.show {
  display: block;
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: var(--spacing-3) var(--spacing-4);
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  color: var(--text-primary);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition:
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    background-color var(--transition-base);
  min-height: var(--touch-target-min);
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--focus-ring);
}

.form-input:disabled,
.form-select:disabled,
.form-textarea:disabled {
  background-color: var(--bg-tertiary);
  color: var(--text-disabled);
  cursor: not-allowed;
}

.form-input::placeholder,
.form-textarea::placeholder {
  color: var(--text-muted);
}

.form-textarea {
  resize: vertical;
  min-height: 120px;
  line-height: var(--line-height-relaxed);
}

.form-input.invalid,
.form-select.invalid,
.form-textarea.invalid {
  border-color: var(--color-error);
  box-shadow: 0 0 0 3px var(--color-error-bg);
}

.form-input.valid,
.form-select.valid,
.form-textarea.valid {
  border-color: var(--color-success);
  box-shadow: 0 0 0 3px var(--color-success-bg);
}

/* Checkbox & Radio */
.form-checkbox,
.form-radio {
  width: 20px;
  height: 20px;
  accent-color: var(--color-primary);
  cursor: pointer;
}

/* ========================================
   NAVIGATION
   ======================================== */

/* Navbar */
.navbar {
  background-color: var(--bg-backdrop);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
}

.navbar-content {
  max-width: var(--max-width-xl);
  margin: 0 auto;
  padding: var(--spacing-4) var(--spacing-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.navbar-brand {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  color: var(--text-primary);
  text-decoration: none;
}

.navbar-nav {
  display: flex;
  gap: var(--spacing-2);
}

.nav-link {
  padding: var(--spacing-2) var(--spacing-4);
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

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

/* Sidebar */
.sidebar {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-5);
  max-height: calc(100vh - var(--spacing-16));
  overflow-y: auto;
}

.sidebar-title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  color: var(--text-primary);
  margin-bottom: var(--spacing-4);
  padding-bottom: var(--spacing-3);
  border-bottom: 2px solid var(--color-primary);
}

/* Chapter List */
.chapter-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.chapter-item {
  padding: var(--spacing-3) var(--spacing-4);
  margin-bottom: var(--spacing-2);
  background-color: var(--bg-secondary);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-base);
  border-left: 3px solid transparent;
}

.chapter-item:hover {
  background-color: var(--bg-tertiary);
  border-left-color: var(--color-primary);
}

.chapter-item.active {
  background-color: var(--color-primary-bg);
  border-left-color: var(--color-primary);
  font-weight: var(--font-weight-semibold);
}

.chapter-item.failed {
  opacity: 0.6;
  background-color: var(--color-warning-bg);
}

/* ========================================
   BOTTOM NAVIGATION (Mobile)
   ======================================== */

.bottom-nav {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: var(--bg-elevated);
  border-top: 1px solid var(--border-color);
  padding: var(--spacing-2) 0;
  z-index: var(--z-fixed);
  box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.1);
}

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

.bottom-nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--spacing-2);
  color: var(--text-secondary);
  text-decoration: none;
  font-size: var(--font-size-xs);
  gap: var(--spacing-1);
  min-width: 60px;
  transition: color var(--transition-fast);
}

.bottom-nav-item.active {
  color: var(--color-primary);
}

.bottom-nav-icon {
  font-size: var(--font-size-2xl);
}

/* ========================================
   PROGRESS BAR
   ======================================== */

.progress-bar {
  width: 100%;
  height: 8px;
  background-color: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar-sm {
  height: 4px;
}

.progress-bar-lg {
  height: 12px;
}

.progress-fill {
  height: 100%;
  background-color: var(--color-primary);
  transition: width var(--transition-slow);
  border-radius: var(--radius-full);
}

/* Reading Progress Bar (top of page) */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background-color: var(--bg-tertiary);
  z-index: var(--z-modal);
}

.reading-progress-fill {
  height: 100%;
  background-color: var(--color-primary);
  transition: width var(--transition-base);
}

/* ========================================
   ALERTS & NOTIFICATIONS
   ======================================== */

.alert {
  padding: var(--spacing-4) var(--spacing-5);
  border-radius: var(--radius-md);
  border-left: 4px solid;
  margin-bottom: var(--spacing-4);
  box-shadow: var(--shadow-xs);
  line-height: var(--line-height-relaxed);
}

.alert-success {
  background-color: var(--color-success-bg);
  border-color: var(--color-success);
  color: var(--color-alert-success-text);
}

.alert-warning {
  background-color: var(--color-warning-bg);
  border-color: var(--color-warning);
  color: var(--color-alert-warning-text);
}

.alert-error {
  background-color: var(--color-error-bg);
  border-color: var(--color-error);
  color: var(--color-alert-error-text);
}

.alert-info {
  background-color: var(--color-info-bg);
  border-color: var(--color-info);
  color: var(--color-alert-info-text);
}

/* ========================================
   TABLES
   ======================================== */

.table-wrapper {
  width: 100%;
  overflow-x: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  background: var(--bg-elevated);
}

.table-wrapper table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  min-width: 640px;
}

.table-wrapper th,
.table-wrapper td {
  padding: var(--spacing-3) var(--spacing-4);
  text-align: left;
  border-bottom: 1px solid var(--border-color-light);
  vertical-align: middle;
}

.table-wrapper th {
  background: var(--color-secondary-bg);
  color: var(--text-primary);
  font-weight: var(--font-weight-semibold);
  font-size: var(--font-size-sm);
  position: sticky;
  top: 0;
  z-index: var(--z-base);
}

.table-wrapper td {
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
}

.table-wrapper tr:last-child td {
  border-bottom: none;
}

.table-wrapper tbody tr:nth-child(even) td {
  background: var(--bg-secondary);
}

.table-wrapper tbody tr:hover td {
  background: var(--color-primary-bg);
}

/* ========================================
   BADGES
   ======================================== */

.badge {
  display: inline-flex;
  align-items: center;
  padding: var(--spacing-1) var(--spacing-3);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-full);
}

.badge-primary {
  background-color: var(--color-primary-bg);
  color: var(--color-primary);
}

.badge-success {
  background-color: var(--color-success-bg);
  color: var(--color-success);
}

.badge-warning {
  background-color: var(--color-warning-bg);
  color: var(--color-warning);
}

.badge-error {
  background-color: var(--color-error-bg);
  color: var(--color-error);
}

/* ========================================
   UTILITIES
   ======================================== */

/* Spacing */
.mt-0 { margin-top: var(--spacing-0); }
.mt-1 { margin-top: var(--spacing-1); }
.mt-2 { margin-top: var(--spacing-2); }
.mt-3 { margin-top: var(--spacing-3); }
.mt-4 { margin-top: var(--spacing-4); }
.mt-5 { margin-top: var(--spacing-5); }
.mt-6 { margin-top: var(--spacing-6); }
.mt-8 { margin-top: var(--spacing-8); }

.mb-0 { margin-bottom: var(--spacing-0); }
.mb-1 { margin-bottom: var(--spacing-1); }
.mb-2 { margin-bottom: var(--spacing-2); }
.mb-3 { margin-bottom: var(--spacing-3); }
.mb-4 { margin-bottom: var(--spacing-4); }
.mb-5 { margin-bottom: var(--spacing-5); }
.mb-6 { margin-bottom: var(--spacing-6); }
.mb-8 { margin-bottom: var(--spacing-8); }

.p-0 { padding: var(--spacing-0); }
.p-1 { padding: var(--spacing-1); }
.p-2 { padding: var(--spacing-2); }
.p-3 { padding: var(--spacing-3); }
.p-4 { padding: var(--spacing-4); }
.p-5 { padding: var(--spacing-5); }
.p-6 { padding: var(--spacing-6); }
.p-8 { padding: var(--spacing-8); }

/* Text */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.text-primary { color: var(--text-primary); }
.text-secondary { color: var(--text-secondary); }
.text-tertiary { color: var(--text-tertiary); }

.font-semibold { font-weight: var(--font-weight-semibold); }
.font-bold { font-weight: var(--font-weight-bold); }

/* Display */
.hidden { display: none !important; }
.block { display: block; }
.inline-block { display: inline-block; }
.flex { display: flex; }
.inline-flex { display: inline-flex; }
.grid { display: grid; }

/* Flex */
.flex-col { flex-direction: column; }
.flex-row { flex-direction: row; }
.items-center { align-items: center; }
.items-start { align-items: flex-start; }
.items-end { align-items: flex-end; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.justify-start { justify-content: flex-start; }
.justify-end { justify-content: flex-end; }
.gap-1 { gap: var(--spacing-1); }
.gap-2 { gap: var(--spacing-2); }
.gap-3 { gap: var(--spacing-3); }
.gap-4 { gap: var(--spacing-4); }
.gap-5 { gap: var(--spacing-5); }
.gap-6 { gap: var(--spacing-6); }

/* Width */
.w-full { width: 100%; }
.max-w-sm { max-width: var(--max-width-sm); }
.max-w-md { max-width: var(--max-width-md); }
.max-w-lg { max-width: var(--max-width-lg); }
.max-w-xl { max-width: var(--max-width-xl); }

/* Overflow */
.overflow-hidden { overflow: hidden; }
.overflow-auto { overflow: auto; }
.overflow-y-auto { overflow-y: auto; }

/* Position */
.relative { position: relative; }
.absolute { position: absolute; }
.fixed { position: fixed; }
.sticky { position: sticky; }

/* Border */
.rounded { border-radius: var(--radius-md); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-full { border-radius: var(--radius-full); }

/* Shadow */
.shadow-sm { box-shadow: var(--shadow-sm); }
.shadow { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }
.shadow-xl { box-shadow: var(--shadow-xl); }

/* ========================================
   RESPONSIVE DESIGN
   ======================================== */

/* --- Tablet (max-width: 768px) --- */
@media (max-width: 768px) {
  /* Bottom Nav - Mobile Only */
  .bottom-nav {
    display: block;
  }

  body {
    padding-bottom: 64px; /* Space for bottom nav */
  }

  :root {
    --font-size-5xl: 2.25rem;
    --font-size-4xl: 1.875rem;
    --container-padding-inline: clamp(10px, 4vw, 20px);
  }

  .card {
    padding: var(--spacing-4);
  }

  /* Navbar: compact on mobile */
  .navbar-content {
    padding: var(--spacing-3) var(--spacing-4);
  }

  .navbar-brand {
    font-size: var(--font-size-lg);
  }

  .navbar-nav {
    gap: var(--spacing-1);
  }

  .nav-link {
    padding: var(--spacing-2) var(--spacing-3);
    font-size: var(--font-size-sm);
  }

  /* Sidebar: scrollable with fade hint */
  .sidebar {
    max-height: 40vh;
    border-radius: var(--radius-md);
    padding: var(--spacing-4);
  }

  .sidebar-title {
    font-size: var(--font-size-base);
    margin-bottom: var(--spacing-3);
    padding-bottom: var(--spacing-2);
  }

  .chapter-item {
    padding: var(--spacing-2) var(--spacing-3);
    font-size: var(--font-size-sm);
  }

  /* Settings panel: prevent overlap with bottom nav */
  .settings-panel-floating {
    top: var(--spacing-2);
    right: var(--spacing-2);
    padding: var(--spacing-2) var(--spacing-3);
  }

  .settings-label {
    display: none;
  }

  .settings-divider {
    margin: 0 var(--spacing-1);
  }

  /* Hero: tighter on mobile */
  .hero {
    padding: var(--spacing-8) var(--spacing-4);
  }

  .hero-title {
    font-size: var(--font-size-3xl);
  }

  .hero-subtitle {
    font-size: var(--font-size-base);
  }

  /* Grid: single column on mobile */
  .grid-auto-fill {
    grid-template-columns: 1fr;
    gap: var(--spacing-4);
  }

  /* Pagination: compact */
  .pagination {
    gap: var(--spacing-1);
  }

  .pagination-btn {
    padding: var(--spacing-2) var(--spacing-3);
    min-width: 36px;
    font-size: var(--font-size-sm);
  }

  /* Table: responsive scroll */
  .table-wrapper {
    -webkit-overflow-scrolling: touch;
  }

  /* Drawer: avoid conflict with bottom nav */
  .drawer {
    bottom: 0;
  }
}

/* --- Small Mobile (max-width: 480px) --- */
@media (max-width: 480px) {
  :root {
    --font-size-5xl: 1.875rem;
    --font-size-4xl: 1.5rem;
    --font-size-3xl: 1.375rem;
    --container-padding-inline: clamp(8px, 3.5vw, 14px);
  }

  .card {
    padding: var(--spacing-3);
    border-radius: var(--radius-md);
  }

  .btn {
    width: 100%;
  }

  .btn-sm {
    width: auto;
  }

  /* Bottom nav: tighter */
  .bottom-nav-item {
    font-size: 10px;
    min-width: 48px;
  }

  .bottom-nav-icon {
    font-size: var(--font-size-xl);
  }

  /* Sidebar: minimal */
  .sidebar {
    max-height: 35vh;
    padding: var(--spacing-3);
  }

  /* Segmented control: compact */
  .segmented-control-item {
    padding: var(--spacing-1) var(--spacing-3);
    font-size: var(--font-size-xs);
  }
}

/* ========================================
   ANIMATIONS
   ======================================== */

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes slideUp {
  from {
    transform: translateY(20px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

@keyframes spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

.animate-fadeIn {
  animation: fadeIn var(--transition-base);
}

.animate-slideUp {
  animation: slideUp var(--transition-base);
}

/* Spinner */
.spinner {
  border: 3px solid var(--bg-tertiary);
  border-top-color: var(--color-primary);
  border-radius: var(--radius-full);
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
}

.spinner-sm {
  width: 24px;
  height: 24px;
  border-width: 2px;
}

.spinner-lg {
  width: 60px;
  height: 60px;
  border-width: 4px;
}

/* ========================================
   GRIDS
   ======================================== */

.grid-auto-fill {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--spacing-5);
}

/* ========================================
   DRAWER (Mobile Navigation)
   ======================================== */

.drawer {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: var(--bg-elevated);
  border-top: 1px solid var(--border-color);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  max-height: 70vh;
  overflow-y: auto;
  transform: translateY(100%);
  transition: transform var(--transition-base);
  z-index: var(--z-modal);
  box-shadow: var(--shadow-2xl);
}

.drawer.open {
  transform: translateY(0);
}

.drawer-backdrop {
  position: fixed;
  inset: 0;
  background-color: var(--bg-overlay);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
  z-index: var(--z-modal-backdrop);
}

.drawer-backdrop.open {
  opacity: 1;
  pointer-events: auto;
}

.drawer-handle {
  width: 40px;
  height: 4px;
  background-color: var(--border-color);
  border-radius: var(--radius-full);
  margin: var(--spacing-3) auto;
}

/* ========================================
   SEARCH BAR
   ======================================== */

.search-bar {
  position: relative;
  max-width: 600px;
  margin: var(--spacing-4) auto;
}

.search-input {
  width: 100%;
  padding: var(--spacing-3) var(--spacing-10) var(--spacing-3) var(--spacing-4);
  font-size: var(--font-size-base);
  color: var(--text-primary);
  background-color: var(--bg-elevated);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-full);
  transition: all var(--transition-base);
}

.search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-bg);
}

.search-icon {
  position: absolute;
  right: var(--spacing-4);
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-tertiary);
  pointer-events: none;
  font-size: var(--font-size-lg);
}

/* ========================================
   PAGINATION
   ======================================== */

.pagination {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: var(--spacing-2);
  flex-wrap: wrap;
}

.pagination-btn {
  padding: var(--spacing-2) var(--spacing-4);
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  cursor: pointer;
  transition: all var(--transition-base);
  min-width: 40px;
}

.pagination-btn:hover:not(:disabled) {
  background-color: var(--bg-tertiary);
  border-color: var(--border-color-dark);
}

.pagination-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.pagination-btn.active {
  background-color: var(--color-primary);
  color: var(--color-white);
  border-color: var(--color-primary);
}

/* ========================================
   HERO SECTION
   ======================================== */

.hero {
  text-align: center;
  padding: var(--spacing-12) var(--spacing-6);
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
  color: var(--color-white);
  border-radius: 0 0 var(--radius-2xl) var(--radius-2xl);
  margin-bottom: var(--spacing-8);
}

.hero-title {
  font-size: var(--font-size-5xl);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--spacing-3);
  text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.hero-subtitle {
  font-size: var(--font-size-lg);
  opacity: 0.95;
  margin-bottom: var(--spacing-6);
}

/* ========================================
   TOGGLE SWITCH - iOS Style
   ======================================== */

.toggle-switch {
  position: relative;
  display: inline-block;
  width: 51px;
  height: 31px;
  flex-shrink: 0;
}

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

.toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--color-gray-300);
  transition: all var(--transition-slow);
  border-radius: var(--radius-full);
}

.toggle-slider:before {
  position: absolute;
  content: "";
  height: 25px;
  width: 25px;
  left: 3px;
  bottom: 3px;
  background-color: var(--color-white);
  transition: all var(--transition-slow);
  border-radius: 50%;
  box-shadow: var(--shadow-sm);
}

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

.toggle-switch input:checked + .toggle-slider:before {
  transform: translateX(20px);
}

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

/* Toggle with icons */
.toggle-switch-icon {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  font-size: var(--font-size-sm);
  pointer-events: none;
  transition: opacity var(--transition-slow);
  z-index: 1;
}

.toggle-switch-icon.toggle-icon-left {
  left: 6px;
  color: var(--color-gray-500);
}

.toggle-switch-icon.toggle-icon-right {
  right: 6px;
  color: var(--color-white);
  opacity: 0;
}

.toggle-switch input:checked + .toggle-slider .toggle-icon-left {
  opacity: 0;
}

.toggle-switch input:checked + .toggle-slider .toggle-icon-right {
  opacity: 1;
}

/* ========================================
   LANGUAGE SWITCHER - Segmented Control
   ======================================== */

.segmented-control {
  display: inline-flex;
  background-color: var(--color-gray-200);
  border-radius: var(--radius-full);
  padding: 3px;
  position: relative;
  box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
}

.segmented-control-item {
  position: relative;
  padding: var(--spacing-1) var(--spacing-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--text-secondary);
  background: transparent;
  border: none;
  border-radius: calc(var(--radius-full) - 2px);
  cursor: pointer;
  transition: all var(--transition-base);
  display: flex;
  align-items: center;
  gap: var(--spacing-1);
  white-space: nowrap;
}

.segmented-control-item:hover {
  color: var(--text-primary);
}

.segmented-control-item.active {
  background-color: var(--color-white);
  color: var(--text-primary);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.segmented-control-item .flag-icon {
  font-size: var(--font-size-base);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.25em;
  height: 1.25em;
  line-height: 1;
  flex-shrink: 0;
  transform: none;
}

/* Dark mode for segmented control */
@media (prefers-color-scheme: dark) {
  .segmented-control {
    background-color: var(--color-gray-700);
  }

  .segmented-control-item.active {
    background-color: var(--color-gray-800);
  }
}

@media (max-width: 768px) {
  .segmented-control-item {
    justify-content: center;
    min-width: 40px;
  }

  .app-shell .settings-panel-inline {
    width: 100%;
    display: flex;
    justify-content: center;
  }

  .app-shell .settings-panel {
    width: auto;
    max-width: 100%;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    padding: 4px 8px;
    border-radius: 14px;
  }

  .app-shell .settings-panel .settings-item {
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .app-shell .settings-panel .settings-divider {
    display: block;
    height: 24px;
    opacity: 0.6;
  }

  .app-shell .settings-panel .segmented-control {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2px;
    padding: 2px;
    height: auto;
  }

  .app-shell .settings-panel .segmented-control-item {
    min-width: 54px;
    min-height: 30px;
    padding: 0 8px;
    border-radius: 10px;
    justify-content: center;
    align-items: center;
    gap: 4px;
    line-height: 1;
  }

  .app-shell .settings-panel .segmented-control-item .flag-icon {
    width: 1.1em;
    height: 1.1em;
    line-height: 1;
    transform: none;
  }

  .app-shell .settings-panel .segmented-control-item span:not(.flag-icon) {
    display: inline;
    font-size: 11px;
    line-height: 1;
  }
}

/* ========================================
   SETTINGS CONTROL PANEL
   ======================================== */

.settings-panel {
  display: flex;
  align-items: center;
  gap: var(--spacing-4);
  padding: var(--spacing-3) var(--spacing-4);
  background-color: var(--bg-elevated);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color-light);
}

.settings-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
}

.settings-label {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--text-secondary);
}

.settings-divider {
  width: 1px;
  height: 24px;
  background-color: var(--border-color);
  margin: 0 var(--spacing-2);
}

/* Floating settings panel - fixed position */
.settings-panel-floating {
  position: fixed;
  top: var(--spacing-4);
  right: var(--spacing-4);
  z-index: var(--z-fixed);
  backdrop-filter: blur(10px);
  background-color: var(--bg-backdrop);
}

/* ========================================
   APP SHELL (Home / Library Shared Layout)
   ======================================== */

.app-shell {
  min-height: 100vh;
  background:
    radial-gradient(circle at 12% -8%, rgba(91, 198, 255, 0.26), transparent 42%),
    radial-gradient(circle at 96% 4%, rgba(0, 194, 255, 0.18), transparent 36%),
    linear-gradient(142deg, #06163d 0%, #0b3e9f 44%, #0f6cff 74%, #00c2ff 100%);
  padding: clamp(var(--spacing-2), 2vw, var(--spacing-5));
}

.app-shell .container {
  width: min(100% - (var(--container-padding-inline) * 2), var(--container-max-width-wide));
  margin-inline: auto;
}

.app-shell .hero,
.app-shell .hero-section {
  color: var(--color-white);
  margin-bottom: var(--spacing-4);
  position: sticky;
  top: 0;
  z-index: calc(var(--z-sticky) + 1);
  padding: 0;
  background: transparent;
}

.app-shell .hero-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-3);
  margin-bottom: 0;
  padding: var(--spacing-3) clamp(var(--spacing-3), 2.4vw, var(--spacing-5));
  background: linear-gradient(120deg, rgba(6, 29, 82, 0.82), rgba(15, 108, 255, 0.7), rgba(0, 194, 255, 0.56));
  backdrop-filter: blur(14px);
  border: 1px solid rgba(145, 224, 255, 0.32);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
}

.app-shell .hero-title-group {
  display: flex;
  align-items: baseline;
  gap: var(--spacing-3);
  min-width: 0;
  flex: 1;
}

.app-shell .hero-title {
  margin: 0;
  font-size: clamp(1rem, 2vw, 1.5rem);
  line-height: var(--line-height-tight);
  color: var(--color-white);
  text-shadow: 0 1px 2px rgba(3, 10, 24, 0.45);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.app-shell .hero-subtitle {
  margin: 0;
  color: rgba(255, 255, 255, 0.92);
  opacity: 0.88;
  font-size: var(--font-size-sm);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Home and library pages keep full title/subtitle visible on desktop */
@media (min-width: 769px) {
  .app-shell-home .hero-header,
  .app-shell-library .hero-header {
    align-items: flex-start;
  }

  .app-shell-home .hero-title-group,
  .app-shell-library .hero-title-group {
    flex-direction: column;
    align-items: flex-start;
    gap: 2px;
    max-width: min(60vw, 780px);
  }

  .app-shell-home .hero-title,
  .app-shell-home .hero-subtitle,
  .app-shell-library .hero-title,
  .app-shell-library .hero-subtitle {
    white-space: normal;
    overflow: visible;
    text-overflow: clip;
  }
}

.app-shell .hero-controls {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  flex-wrap: wrap;
  gap: var(--spacing-2);
}

.app-shell .control-divider {
  width: 1px;
  height: 22px;
  background-color: rgba(255, 255, 255, 0.25);
}

.app-shell .nav-buttons {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  flex-wrap: wrap;
}

.app-shell .nav-btn,
.app-shell .auth-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-1);
  min-height: var(--touch-target-min);
  padding: var(--spacing-2) var(--spacing-4);
  border-radius: var(--radius-full);
  border: 1px solid rgba(255, 255, 255, 0.28);
  background: rgba(255, 255, 255, 0.14);
  color: var(--color-white);
  font-size: var(--font-size-sm);
  text-decoration: none;
  cursor: pointer;
  transition:
    transform var(--transition-fast),
    background-color var(--transition-base),
    border-color var(--transition-base),
    box-shadow var(--transition-base);
}

.app-shell .nav-btn:hover,
.app-shell .auth-btn:hover {
  text-decoration: none;
  color: var(--color-white);
  background: rgba(255, 255, 255, 0.22);
  border-color: rgba(255, 255, 255, 0.4);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.app-shell .auth-btn.logout {
  background: rgba(244, 67, 54, 0.22);
  border-color: rgba(244, 67, 54, 0.38);
}

.app-shell .auth-btn.logout:hover {
  background: rgba(244, 67, 54, 0.3);
}

.app-shell .user-info-bar {
  display: flex;
  align-items: center;
  gap: var(--spacing-3);
  padding: var(--spacing-2) var(--spacing-4);
  border-radius: var(--radius-full);
  border: 1px solid rgba(255, 255, 255, 0.25);
  background: rgba(255, 255, 255, 0.12);
  backdrop-filter: blur(10px);
}

.app-shell .user-info {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  color: var(--color-white);
  font-size: var(--font-size-sm);
}

.app-shell .user-avatar {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: var(--font-weight-bold);
  font-size: var(--font-size-sm);
  color: var(--color-white);
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.32), rgba(255, 255, 255, 0.12));
}

.app-shell .user-name {
  font-weight: var(--font-weight-semibold);
}

.app-shell .user-role {
  padding: 2px var(--spacing-2);
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.2);
  color: var(--color-white);
  font-size: var(--font-size-xs);
}

.app-shell .auth-buttons {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  flex-wrap: wrap;
}

.app-shell .settings-panel-inline {
  display: flex;
  align-items: center;
}

.app-shell .settings-panel-inline .settings-panel {
  background: rgba(255, 255, 255, 0.14);
  border: 1px solid rgba(255, 255, 255, 0.24);
  box-shadow: var(--shadow-sm);
}

.app-shell .settings-panel {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  padding: var(--spacing-2) var(--spacing-3);
  border-radius: var(--radius-full);
}

.app-shell .settings-divider {
  width: 1px;
  height: 18px;
  margin: 0 var(--spacing-1);
  background-color: rgba(255, 255, 255, 0.24);
}

.app-shell .bottom-nav {
  background-color: var(--bg-backdrop);
  border-top: 1px solid var(--border-color);
  backdrop-filter: blur(12px);
  padding-bottom: max(var(--spacing-2), env(safe-area-inset-bottom));
}

.app-shell .bottom-nav-item {
  min-height: var(--touch-target-min);
  border-radius: var(--radius-md);
}

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

@media (max-width: 768px) {
  .app-shell {
    padding: var(--spacing-2);
    padding-bottom: calc(72px + env(safe-area-inset-bottom));
  }

  .app-shell .hero,
  .app-shell .hero-section {
    position: static;
    margin-bottom: var(--spacing-3);
  }

  .app-shell .hero-header {
    flex-direction: column;
    align-items: stretch;
    gap: var(--spacing-2);
    padding: var(--spacing-2) var(--spacing-3);
    border-radius: var(--radius-lg);
  }

  .app-shell .hero-title-group {
    width: 100%;
    align-items: center;
    justify-content: space-between;
  }

  .app-shell .hero-title {
    font-size: var(--font-size-base);
  }

  .app-shell .hero-subtitle {
    display: none;
  }

  .app-shell .hero-controls {
    width: 100%;
    flex-direction: column;
    align-items: stretch;
    gap: var(--spacing-2);
  }

  .app-shell .nav-buttons,
  .app-shell .settings-panel-inline,
  .app-shell .settings-panel,
  .app-shell .user-info-bar {
    width: 100%;
  }

  .app-shell .nav-btn {
    flex: 1 1 auto;
  }

  .app-shell .user-info-bar {
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--spacing-2);
    border-radius: var(--radius-lg);
  }

  .app-shell .auth-buttons {
    width: 100%;
    justify-content: center;
  }

  .app-shell .auth-btn {
    flex: 1 1 120px;
  }

  .app-shell .settings-panel-inline {
    order: -1;
  }

  .app-shell .settings-panel {
    justify-content: center;
    gap: var(--spacing-2);
  }

  .app-shell .control-divider,
  .app-shell .settings-divider {
    display: none;
  }

  .app-shell .settings-panel-inline,
  .app-shell .settings-panel {
    width: auto;
  }

  .app-shell .settings-panel {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    padding: 4px 8px;
    border-radius: 14px;
  }

  .app-shell .settings-panel .settings-divider {
    display: block;
    height: 24px;
    opacity: 0.6;
  }

  .app-shell .settings-panel .segmented-control {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2px;
    padding: 2px;
  }

  .app-shell .settings-panel .segmented-control-item {
    min-width: 54px;
    min-height: 30px;
    padding: 0 8px;
    border-radius: 10px;
    justify-content: center;
    gap: 4px;
    line-height: 1;
  }

  .app-shell .settings-panel .segmented-control-item .flag-icon {
    width: 1.1em;
    height: 1.1em;
    line-height: 1;
    transform: none;
  }

  .app-shell .settings-panel .segmented-control-item span:not(.flag-icon) {
    display: inline;
    font-size: 11px;
    line-height: 1;
  }

  .app-shell-home .hero-title,
  .app-shell-library .hero-title {
    white-space: normal;
    overflow: visible;
    text-overflow: clip;
    line-height: var(--line-height-tight);
  }

  .app-shell-home .hero-title-group,
  .app-shell-library .hero-title-group {
    align-items: flex-start;
    justify-content: flex-start;
  }
}

/* ========================================
   AUTH SHELL (Login / Register)
   ======================================== */

.auth-shell {
  min-height: 100vh;
  padding: clamp(var(--spacing-2), 3vw, var(--spacing-6));
  display: flex;
  align-items: center;
  justify-content: center;
  background:
    radial-gradient(circle at 18% 18%, rgba(255, 255, 255, 0.22), transparent 35%),
    radial-gradient(circle at 85% 0%, rgba(15, 108, 255, 0.2), transparent 42%),
    linear-gradient(140deg, #07225f 0%, #0f6cff 46%, #00c2ff 100%);
}

.auth-shell .login-container,
.auth-shell .register-container {
  width: min(100%, 520px);
  max-height: min(92vh, 860px);
  overflow-y: auto;
  background: var(--bg-elevated);
  border: 1px solid var(--border-color-light);
  border-radius: var(--radius-xl);
  padding: clamp(var(--spacing-4), 3vw, var(--spacing-8));
  box-shadow: var(--shadow-2xl);
}

.auth-shell .logo {
  margin-bottom: var(--spacing-6);
}

.auth-shell .logo-icon {
  filter: drop-shadow(0 8px 16px rgba(15, 108, 255, 0.24));
}

.auth-shell h1 {
  margin-bottom: var(--spacing-2);
  font-size: clamp(1.5rem, 3.2vw, 2.1rem);
}

.auth-shell .subtitle {
  margin-bottom: var(--spacing-5);
}

.auth-shell .guest-notice,
.auth-shell .password-requirements {
  border: 1px solid var(--border-color-light);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-xs);
}

.auth-shell .divider {
  margin: var(--spacing-5) 0;
}

.auth-shell .register-link,
.auth-shell .login-link,
.auth-shell .back-link {
  margin-top: var(--spacing-4);
}

@media (max-width: 768px) {
  .auth-shell {
    align-items: flex-start;
    padding-top: var(--spacing-4);
  }

  .auth-shell .login-container,
  .auth-shell .register-container {
    width: 100%;
  }
}

/* ========================================
   PAGE SHELL (Orders / Purchase / Admin)
   ======================================== */

.page-shell {
  min-height: 100vh;
  padding: clamp(var(--spacing-3), 2.6vw, var(--spacing-6));
  background: var(--bg-base);
}

.page-shell.page-shell-gradient {
  background:
    radial-gradient(circle at 50% -20%, rgba(255, 255, 255, 0.3), transparent 48%),
    linear-gradient(145deg, #0d2f7f 0%, #0f62fe 55%, #1a78f8 100%);
}

.page-shell .container {
  width: min(100% - (var(--container-padding-inline) * 2), var(--container-max-width-wide));
  margin-inline: auto;
}

.page-shell .page-header {
  margin-bottom: var(--spacing-7);
}

.page-shell.page-shell-center-header .page-header {
  text-align: center;
  color: var(--color-white);
}

.page-shell .page-header h1 {
  font-size: clamp(1.6rem, 3.4vw, 2.25rem);
  margin-bottom: var(--spacing-2);
}

.page-shell .page-header p {
  font-size: var(--font-size-base);
  margin-bottom: 0;
}

.page-shell .back-link {
  margin-top: var(--spacing-3);
}

.page-shell .back-link a {
  display: inline-flex;
  align-items: center;
  min-height: var(--touch-target-min);
  padding: var(--spacing-2) var(--spacing-4);
  border-radius: var(--radius-full);
  border: 1px solid var(--border-color);
  background: var(--bg-elevated);
  color: var(--text-primary);
  text-decoration: none;
  transition: all var(--transition-base);
}

.page-shell.page-shell-gradient .back-link a {
  background: rgba(255, 255, 255, 0.14);
  border-color: rgba(255, 255, 255, 0.34);
  color: var(--color-white);
}

.page-shell .back-link a:hover {
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.page-shell .order-card,
.page-shell .package-card,
.page-shell .stat-card,
.page-shell .data-table,
.page-shell .quota-info,
.page-shell .modal-content {
  border: 1px solid var(--border-color-light);
  box-shadow: var(--shadow-sm);
}

.page-shell .order-card:hover,
.page-shell .package-card:hover,
.page-shell .stat-card:hover {
  box-shadow: var(--shadow-md);
}

.page-shell .tab {
  min-height: var(--touch-target-min);
  border-radius: var(--radius-md) var(--radius-md) 0 0;
}

.page-shell .btn,
.page-shell .btn-purchase,
.page-shell .tab,
.page-shell .search-input {
  min-height: var(--touch-target-min);
}

.page-shell .table-wrapper {
  border-radius: var(--radius-lg);
}

.page-shell .table-wrapper table {
  min-width: 760px;
}

.page-shell.page-shell-purchase .packages-grid {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.page-shell.page-shell-purchase .quota-remaining {
  font-size: clamp(2rem, 8vw, 3rem);
}

@media (max-width: 768px) {
  .page-shell {
    padding: var(--spacing-3) var(--spacing-2);
  }

  .page-shell .container {
    width: 100%;
  }

  .page-shell .page-header {
    margin-bottom: var(--spacing-5);
  }

  .page-shell .tabs {
    gap: var(--spacing-1);
    margin-bottom: var(--spacing-5);
  }

  .page-shell .order-actions {
    flex-wrap: wrap;
  }
}

@media (max-width: 480px) {
  .page-shell .page-header h1 {
    font-size: var(--font-size-2xl);
  }

  .page-shell .back-link a {
    width: 100%;
    justify-content: center;
  }
}

/* ========================================
   READER SHELL
   ======================================== */

.reader-shell {
  min-height: 100vh;
  background:
    radial-gradient(circle at 90% -10%, rgba(15, 108, 255, 0.14), transparent 35%),
    linear-gradient(180deg, var(--bg-secondary), var(--bg-primary));
}

.reader-shell .header {
  position: sticky;
  top: 0;
  z-index: calc(var(--z-sticky) + 1);
  padding: var(--spacing-3) var(--spacing-4);
  border-bottom: 1px solid rgba(255, 255, 255, 0.18);
  background: linear-gradient(125deg, rgba(8, 36, 96, 0.9), rgba(15, 108, 255, 0.8), rgba(0, 194, 255, 0.62));
  backdrop-filter: blur(10px);
}

.reader-shell .header-content {
  max-width: var(--container-max-width-wide);
  margin: 0 auto;
}

.reader-shell .header-toolbar {
  margin-bottom: var(--spacing-2);
  flex-wrap: wrap;
}

.reader-shell .back-link,
.reader-shell .header-btn {
  min-height: var(--touch-target-min);
}

.reader-shell .header-btn {
  padding: var(--spacing-2) var(--spacing-4);
  border: 1px solid rgba(255, 255, 255, 0.28);
  background: rgba(255, 255, 255, 0.14);
  box-shadow: var(--shadow-xs);
}

.reader-shell .book-row {
  align-items: center;
}

.reader-shell .book-title {
  font-size: clamp(1rem, 2.2vw, 1.5rem);
}

.reader-shell .book-meta-item,
.reader-shell .book-status {
  min-height: 22px;
}

.reader-shell .reader-container {
  max-width: var(--container-max-width-wide);
  margin: 0 auto;
  padding: clamp(var(--spacing-3), 2.6vw, var(--spacing-6));
  display: grid;
  grid-template-columns: minmax(240px, 300px) minmax(0, 1fr);
  gap: var(--spacing-5);
  align-items: start;
}

.reader-shell .sidebar,
.reader-shell .content-area {
  border: 1px solid var(--border-color-light);
  box-shadow: var(--shadow-sm);
}

.reader-shell .sidebar {
  position: sticky;
  top: calc(var(--spacing-4) + 72px);
  max-height: calc(100vh - 120px);
}

.reader-shell .chapter-item {
  min-height: var(--touch-target-min);
  display: flex;
  align-items: center;
}

.reader-shell .content-area {
  min-height: 60vh;
  padding: clamp(var(--spacing-4), 3vw, var(--spacing-8));
}

.reader-shell .chapter-header {
  margin-bottom: var(--spacing-6);
  padding-bottom: var(--spacing-4);
}

.reader-shell .chapter-title-display {
  font-size: clamp(1.25rem, 3vw, 2rem);
}

.reader-shell .chapter-content {
  max-width: var(--content-max-readable);
  margin: 0 auto;
  font-size: clamp(14px, 1.05vw, 15px);
  line-height: 1.64;
}

.reader-shell .chapter-content p {
  text-align: left;
}

.reader-shell .chapter-content pre,
.reader-shell .markdown-body pre,
.reader-shell .code-block {
  max-width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.reader-shell .navigation {
  gap: var(--spacing-3);
  flex-wrap: wrap;
}

.reader-shell .nav-button {
  min-height: var(--touch-target-min);
}

.reader-shell .download-menu {
  border: 1px solid var(--border-color-light);
  box-shadow: var(--shadow-xl);
}

.reader-shell .page-footer {
  padding: var(--spacing-6) var(--spacing-4);
}

@media (max-width: 1024px) {
  .reader-shell .reader-container {
    grid-template-columns: 1fr;
    gap: var(--spacing-4);
  }

  .reader-shell .sidebar {
    position: static;
    max-height: 38vh;
  }
}

@media (max-width: 768px) {
  .reader-shell .header {
    padding: var(--spacing-2);
  }

  .reader-shell .header-toolbar {
    gap: var(--spacing-2);
  }

  .reader-shell .toolbar-right {
    width: 100%;
    justify-content: space-between;
    flex-wrap: wrap;
  }

  .reader-shell .header-btn {
    flex: 1 1 128px;
    justify-content: center;
  }

  .reader-shell .toolbar-divider {
    display: none;
  }

  .reader-shell .book-row {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-2);
  }

  .reader-shell .book-sub-row {
    width: 100%;
    white-space: normal;
  }

  .reader-shell .reader-container {
    padding: var(--spacing-3) var(--spacing-2);
  }

  .reader-shell .sidebar,
  .reader-shell .content-area {
    padding: var(--spacing-3);
  }

  .reader-shell .navigation {
    flex-direction: column;
  }

  .reader-shell .nav-button {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .reader-shell .toolbar-settings .segmented-control-item span:not(.flag-icon) {
    display: none;
  }

  .reader-shell .book-meta {
    width: 100%;
  }

  .reader-shell .book-meta-item,
  .reader-shell .book-status {
    font-size: 10px;
  }

  .reader-shell .download-menu {
    min-width: 156px;
  }
}