/* ========================================
   RESET & BASE
   ======================================== */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  touch-action: pan-x pan-y;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  min-height: 100vh;
  transition: background-color 0.3s ease, color 0.3s ease;
  overflow-x: hidden;
}

/* ========================================
   THEME VARIABLES
   ======================================== */
body.light {
  --bg-primary: #fafafa;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f0f0f0;
  --text-primary: #1a1a1a;
  --text-secondary: #6b6b6b;
  --text-muted: #999999;
  --border: #e5e5e5;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --footer-bg: rgba(255, 255, 255, 0.85);
  --footer-border: rgba(0, 0, 0, 0.08);
  --modal-bg: rgba(255, 255, 255, 0.97);
  --modal-overlay: rgba(0, 0, 0, 0.3);
  --shadow: 0 -1px 20px rgba(0, 0, 0, 0.08);
  --card-hover: #f5f5f5;
  --progress-bg: #e5e5e5;
  --progress-fill: #2563eb;
  --input-bg: #f0f0f0;
  --scrollbar-track: #f0f0f0;
  --scrollbar-thumb: #cccccc;
  --pdf-filter: none;
}

body.dark {
  --bg-primary: #0f0f0f;
  --bg-secondary: #1a1a1a;
  --bg-tertiary: #252525;
  --text-primary: #e8e8e8;
  --text-secondary: #a0a0a0;
  --text-muted: #666666;
  --border: #2a2a2a;
  --accent: #3b82f6;
  --accent-hover: #60a5fa;
  --footer-bg: rgba(20, 20, 20, 0.9);
  --footer-border: rgba(255, 255, 255, 0.06);
  --modal-bg: rgba(26, 26, 26, 0.97);
  --modal-overlay: rgba(0, 0, 0, 0.6);
  --shadow: 0 -1px 20px rgba(0, 0, 0, 0.3);
  --card-hover: #222222;
  --progress-bg: #2a2a2a;
  --progress-fill: #3b82f6;
  --input-bg: #252525;
  --scrollbar-track: #1a1a1a;
  --scrollbar-thumb: #444444;
  --pdf-filter: invert(0.85) hue-rotate(180deg);
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: var(--scrollbar-track);
}

::-webkit-scrollbar-thumb {
  background: var(--scrollbar-thumb);
  border-radius: 3px;
}

/* ========================================
   SCREEN MANAGEMENT
   ======================================== */
.screen {
  display: none;
}

.screen.active {
  display: flex;
}

/* ========================================
   WELCOME SCREEN
   ======================================== */
#welcome-screen {
  min-height: 100vh;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}

.welcome-container {
  text-align: center;
  max-width: 480px;
  width: 100%;
  padding: 2rem;
}

.welcome-icon {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
  opacity: 0.6;
}

.welcome-container h1 {
  font-size: 2rem;
  font-weight: 600;
  letter-spacing: -0.03em;
  margin-bottom: 0.5rem;
}

.welcome-subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 2rem;
  font-weight: 300;
}

.upload-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  background-color: var(--accent);
  color: #ffffff;
  border: none;
  border-radius: 12px;
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.2s ease, transform 0.1s ease;
  font-family: inherit;
}

.upload-btn:hover {
  background-color: var(--accent-hover);
  transform: translateY(-1px);
}

.upload-btn:active {
  transform: translateY(0);
}

/* ========================================
   LIBRARY (Welcome + Modal)
   ======================================== */
.library-section {
  margin-top: 2.5rem;
}

.library-section h2 {
  font-size: 0.85rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.library-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.library-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.85rem 1rem;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.15s ease, border-color 0.15s ease;
  text-align: left;
}

.library-item:hover {
  background-color: var(--card-hover);
  border-color: var(--accent);
}

.library-item-icon {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--bg-tertiary);
  border-radius: 8px;
  color: var(--accent);
}

.library-item-info {
  flex: 1;
  min-width: 0;
}

.library-item-name {
  font-size: 0.9rem;
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.library-item-meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.library-item-actions {
  flex-shrink: 0;
  display: flex;
  gap: 0.25rem;
}

.library-item-menu-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px;
  border-radius: 6px;
  transition: color 0.15s ease, background-color 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

/* ========================================
   CONTEXT MENU (hamburger popup)
   ======================================== */
.context-menu {
  position: fixed;
  z-index: 500;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 4px;
  min-width: 160px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}

.context-menu.hidden {
  display: none;
}

.context-menu-item {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  width: 100%;
  padding: 0.6rem 0.75rem;
  border: none;
  background: none;
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.85rem;
  cursor: pointer;
  border-radius: 8px;
  transition: background-color 0.12s ease;
  text-align: left;
}

.context-menu-item:hover {
  background-color: var(--bg-tertiary);
}

.context-menu-danger {
  color: #ef4444;
}

.context-menu-danger:hover {
  background-color: rgba(239, 68, 68, 0.1);
}

/* ========================================
   RENAME MODAL
   ======================================== */
.rename-modal-content {
  max-width: 360px;
}

.rename-input {
  width: 100%;
  padding: 0.7rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background-color: var(--input-bg);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.9rem;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.rename-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.rename-confirm-btn {
  margin-top: 0.75rem;
  width: 100%;
  justify-content: center;
  font-size: 0.85rem;
  padding: 0.65rem 1rem;
}

/* ========================================
   CONFIRM DELETE MODAL
   ======================================== */
.confirm-modal-content {
  max-width: 320px;
  text-align: center;
  padding: 1.75rem 1.5rem 1.25rem;
}

.confirm-message {
  font-size: 0.95rem;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
  line-height: 1.5;
}

.confirm-actions {
  display: flex;
  gap: 0.5rem;
}

.confirm-btn {
  flex: 1;
  padding: 0.6rem 1rem;
  border: none;
  border-radius: 10px;
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.15s ease, transform 0.1s ease;
}

.confirm-btn:active {
  transform: translateY(0);
}

.confirm-btn-cancel {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
}

.confirm-btn-cancel:hover {
  background-color: var(--border);
}

.confirm-btn-danger {
  background-color: #ef4444;
  color: #ffffff;
}

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

/* ========================================
   READER SCREEN
   ======================================== */
#reader-screen {
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
}

.reader-content {
  flex: 1;
  overflow: auto;
  padding: 12px 8px 100px 8px;
  display: flex;
  justify-content: center;
}

.pdf-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.pdf-container canvas {
  display: block;
  border-radius: 2px;
}

/* Dark mode PDF inversion */
body.dark .pdf-container canvas {
  filter: var(--pdf-filter);
}

/* ========================================
   FLOATING FOOTER
   ======================================== */
.reader-footer {
  position: fixed;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 2;
  width: auto;
  max-width: calc(100% - 32px);
}

.footer-inner {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  background-color: var(--footer-bg);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-radius: 16px;
  box-shadow: var(--shadow);
}

.footer-group {
  display: flex;
  align-items: center;
  gap: 4px;
}

.footer-divider {
  width: 1px;
  height: 24px;
  background-color: var(--border);
  margin: 0 4px;
}

.footer-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border: none;
  background: none;
  color: var(--text-primary);
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease;
}

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

.footer-btn:active {
  background-color: var(--border);
}

.page-info {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  font-variant-numeric: tabular-nums;
}

.page-input {
  width: 40px;
  text-align: center;
  border: none;
  background-color: var(--input-bg);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.8rem;
  padding: 4px 2px;
  border-radius: 6px;
  outline: none;
  font-variant-numeric: tabular-nums;
  -moz-appearance: textfield;
}

.page-input::-webkit-inner-spin-button,
.page-input::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.page-input:focus {
  box-shadow: 0 0 0 2px var(--accent);
}

.page-separator {
  color: var(--text-muted);
}

.zoom-info {
  font-size: 0.75rem;
  color: var(--text-secondary);
  min-width: 36px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

/* Progress bar */
.progress-bar-container {
  height: 2px;
  width: calc(100% - 16px);
  position: fixed;
  bottom: 0px;
  left: 50%;
  transform: translateX(-50%);
  background-color: var(--progress-bg);
  border-radius: 0 0 16px 16px;
  overflow: hidden;
  z-index: 3;
}

.progress-bar {
  height: 100%;
  background-color: var(--progress-fill);
  border-radius: 0 0 16px 16px;
  transition: width 0.3s ease;
  width: 0%;
}

/* ========================================
   MODAL
   ======================================== */
.modal {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
}

.modal.hidden {
  display: none;
}

.modal-overlay {
  position: absolute;
  inset: 0;
  background-color: var(--modal-overlay);
  backdrop-filter: blur(4px);
}

.modal-content {
  position: relative;
  background-color: var(--modal-bg);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 1.75rem;
  max-width: 420px;
  width: calc(100% - 32px);
  max-height: 70vh;
  overflow-y: auto;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.25rem;
}

.modal-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
}

.modal-close-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border: none;
  background: none;
  color: var(--text-secondary);
  border-radius: 8px;
  cursor: pointer;
  transition: background-color 0.15s ease;
}

.modal-close-btn:hover {
  background-color: var(--bg-tertiary);
}

.modal-upload {
  margin-top: 1rem;
  width: 100%;
  justify-content: center;
  font-size: 0.85rem;
  padding: 0.65rem 1rem;
}

/* ========================================
   LOADING INDICATOR
   ======================================== */
.loading-overlay {
  position: fixed;
  inset: 0;
  z-index: 300;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--bg-primary);
  opacity: 0.9;
}

.loading-spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

/* ========================================
   UTILITY
   ======================================== */
.hidden {
  display: none !important;
}

/* ========================================
   RESPONSIVE
   ======================================== */
@media (max-width: 600px) {
  .welcome-container h1 {
    font-size: 1.6rem;
  }

  .footer-inner {
    padding: 6px 10px;
    gap: 4px;
  }

  .footer-btn {
    width: 32px;
    height: 32px;
  }

  .footer-divider {
    margin: 0 2px;
  }

  .zoom-info {
    min-width: 30px;
    font-size: 0.7rem;
  }

  .reader-content {
    padding: 8px 4px 90px 4px;
  }

  .reader-footer {
    bottom: 10px;
  }
}

@media (max-width: 380px) {
  .footer-inner {
    flex-wrap: wrap;
    justify-content: center;
    border-radius: 14px;
  }

  .footer-divider {
    display: none;
  }
}