/* ===== CSS Variables ===== */
:root {
  --bg: #0f1117;
  --surface: #161922;
  --card: #1c2030;
  --primary: #7c3aed;
  --primary-hover: #6d28d9;
  --primary-glow: rgba(124, 58, 237, 0.3);
  --secondary: #06b6d4;
  --secondary-glow: rgba(6, 182, 212, 0.3);
  --correct: #22c55e;
  --wrong: #ef4444;
  --highlight: #fbbf24;
  --text: #e8ecf4;
  --text-muted: #7a8299;
  --border: #252a3a;
  --radius: 12px;
  --radius-sm: 8px;
  --radius-lg: 16px;
  --shadow: 0 4px 24px rgba(0,0,0,0.3);
  --transition: 0.2s ease;
  --font-display: 'Syne', sans-serif;
  --font-body: 'Outfit', sans-serif;
  --font-content: 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

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

html { font-size: 16px; -webkit-font-smoothing: antialiased; }

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
  line-height: 1.6;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; font-size: inherit; }

input, textarea { font-family: inherit; color: var(--text); background: var(--card); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 12px 16px; font-size: 0.95rem; outline: none; transition: border-color var(--transition); }
input:focus, textarea:focus { border-color: var(--primary); }

::selection { background: var(--primary); color: #fff; }
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* ===== Views ===== */
.view { display: none; min-height: 100vh; }
.view.active { display: flex; flex-direction: column; }

/* ===== INPUT VIEW ===== */
#input-view {
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
  animation: fadeSlideUp 0.5s ease;
}

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

.input-wrapper {
  width: 100%;
  max-width: 680px;
}

/* Logo */
.logo-section { text-align: center; margin-bottom: 40px; }

.logo {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  margin-bottom: 8px;
}

.logo-icon { width: 44px; height: 44px; }

.logo-text {
  font-family: var(--font-display);
  font-size: 2.4rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tagline {
  color: var(--text-muted);
  font-size: 1.05rem;
  font-weight: 300;
  letter-spacing: 0.5px;
}

/* Language Switcher */
.lang-switcher {
  display: flex;
  gap: 4px;
  justify-content: center;
  margin-top: 12px;
  background: var(--surface);
  border-radius: 50px;
  padding: 3px;
  display: inline-flex;
}

.lang-btn {
  padding: 5px 16px;
  border-radius: 50px;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
  transition: all var(--transition);
  letter-spacing: 0.5px;
}

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

/* Input Tabs */
.input-tabs {
  display: flex;
  gap: 4px;
  background: var(--surface);
  border-radius: 50px;
  padding: 4px;
  margin-bottom: 20px;
}

.input-tab {
  flex: 1;
  padding: 10px 16px;
  border-radius: 50px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  transition: all var(--transition);
  text-align: center;
}

.input-tab:hover { color: var(--text); }
.input-tab.active { background: var(--primary); color: #fff; }

/* Input Panels */
.input-panel { display: none; }
.input-panel.active { display: block; animation: fadeIn 0.25s ease; }

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

/* Textarea */
.textarea-wrapper { position: relative; }

#paste-input {
  width: 100%;
  min-height: 250px;
  max-height: 500px;
  resize: vertical;
  font-family: var(--font-content);
  font-size: 0.95rem;
  line-height: 1.7;
  border-radius: var(--radius);
  padding: 16px;
}

.textarea-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 8px;
  padding: 0 4px;
}

#char-count { font-size: 0.8rem; color: var(--text-muted); }

/* Dropzone */
.dropzone {
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  padding: 48px 24px;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition);
}

.dropzone:hover, .dropzone.dragover {
  border-color: var(--primary);
  background: rgba(124, 58, 237, 0.05);
}

.dropzone-icon { width: 48px; height: 48px; color: var(--text-muted); margin-bottom: 12px; }
.dropzone-text { font-size: 1rem; margin-bottom: 4px; }
.dropzone-hint { font-size: 0.82rem; color: var(--text-muted); }

/* PDF Preview */
.pdf-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 16px;
  background: var(--surface);
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
  font-size: 0.9rem;
}

#pdf-filename { font-weight: 600; }
#pdf-pages { color: var(--text-muted); }

.progress-bar {
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 8px;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 2px;
  transition: width 0.3s ease;
  width: 0%;
}

#pdf-progress-text { font-size: 0.82rem; color: var(--text-muted); }

#pdf-text-preview {
  width: 100%;
  height: 180px;
  resize: none;
  font-size: 0.85rem;
  font-family: var(--font-content);
  margin: 12px 0;
  border-radius: var(--radius-sm);
}

.pdf-actions { display: flex; gap: 8px; }

/* Topic Input */
.topic-input {
  width: 100%;
  padding: 14px 18px;
  font-size: 1rem;
  border-radius: var(--radius);
  margin-bottom: 16px;
}

.topic-categories {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.topic-category {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.topic-category-name {
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin: 0;
}

.topic-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.show-more-topics {
  display: block;
  margin: 14px auto 0;
  padding: 6px 16px;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: 50px;
  font-size: 0.8rem;
  font-weight: 500;
  transition: all var(--transition);
}

.show-more-topics:hover {
  color: var(--primary);
  border-color: var(--primary);
}

.topic-chip {
  padding: 8px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 50px;
  font-size: 0.85rem;
  color: var(--text-muted);
  transition: all var(--transition);
}

.topic-chip:hover {
  border-color: var(--primary);
  color: var(--text);
  background: rgba(124, 58, 237, 0.1);
}

/* Generate Settings */
.generate-settings {
  margin-top: 20px;
  text-align: center;
}

.settings-toggle {
  padding: 8px 18px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: 50px;
  transition: all var(--transition);
}

.settings-toggle:hover { color: var(--text); border-color: var(--text-muted); }
.settings-toggle.open { color: var(--primary); border-color: var(--primary); }

.settings-panel {
  margin-top: 12px;
  padding: 20px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
  text-align: left;
  overflow: hidden;
  animation: settingsSlide 0.25s ease;
}

@keyframes settingsSlide {
  from { opacity: 0; max-height: 0; padding-top: 0; padding-bottom: 0; }
  to { opacity: 1; max-height: 300px; }
}

.setting-group { margin-bottom: 18px; }
.setting-group:last-child { margin-bottom: 0; }

.setting-group-label {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--text);
}

.difficulty-inputs {
  display: flex;
  gap: 16px;
  align-items: center;
  flex-wrap: wrap;
}

.diff-input {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.diff-input label {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.diff-input span {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
}

.diff-input input[type="number"] {
  width: 60px;
  padding: 6px 4px;
  text-align: center;
  font-size: 0.9rem;
  font-weight: 600;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  -moz-appearance: textfield;
}

.diff-input input[type="number"]::-webkit-inner-spin-button,
.diff-input input[type="number"]::-webkit-outer-spin-button {
  opacity: 1;
}

.diff-input input[type="number"]:focus { border-color: var(--primary); }

.diff-dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.diff-dot.easy { background: var(--correct); }
.diff-dot.medium { background: var(--highlight); }
.diff-dot.hard { background: var(--wrong); }

.fc-total {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-left: auto;
  font-weight: 500;
}

@media (max-width: 480px) {
  .difficulty-inputs { gap: 10px; }
  .diff-input input[type="number"] { width: 50px; }
  .fc-total { margin-left: 0; width: 100%; text-align: center; margin-top: 4px; }
}

/* Generate Button */
.btn-generate {
  width: 100%;
  padding: 16px 24px;
  margin-top: 24px;
  background: linear-gradient(135deg, var(--primary), #6d28d9);
  color: #fff;
  font-size: 1.05rem;
  font-weight: 600;
  border-radius: var(--radius);
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.btn-generate:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px var(--primary-glow);
}

.btn-generate:disabled { opacity: 0.7; cursor: not-allowed; transform: none; }

.btn-generate-loading { display: flex; align-items: center; justify-content: center; gap: 10px; }

.spinner { width: 20px; height: 20px; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

.generate-hint {
  text-align: center;
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-top: 8px;
}

/* ===== Buttons ===== */
.btn-primary {
  padding: 10px 20px;
  background: var(--primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.9rem;
  transition: all var(--transition);
}

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

.btn-ghost {
  padding: 8px 16px;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 500;
  transition: all var(--transition);
}

.btn-ghost:hover { color: var(--text); border-color: var(--text-muted); }

.btn-icon {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  font-size: 1.4rem;
  color: var(--text-muted);
  transition: all var(--transition);
}

.btn-icon:hover { background: var(--surface); color: var(--text); }

/* ===== TOP BAR ===== */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.topbar-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  transition: opacity var(--transition);
}

.topbar-logo:hover { opacity: 0.8; }
.topbar-logo-icon { width: 28px; height: 28px; }

.topbar-title {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-muted);
  max-width: 400px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.topbar-actions { display: flex; gap: 8px; align-items: center; }

/* Export Dropdown */
.export-dropdown { position: relative; }

.export-menu {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  min-width: 200px;
  box-shadow: var(--shadow);
  z-index: 200;
  overflow: hidden;
}

.export-menu.open { display: block; }

.export-menu button {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 16px;
  font-size: 0.88rem;
  color: var(--text);
  transition: background var(--transition);
}

.export-menu button:hover { background: var(--surface); }

/* ===== STUDY TABS ===== */
.study-tabs {
  display: flex;
  gap: 0;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.study-tab {
  padding: 14px 24px;
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--text-muted);
  border-bottom: 2px solid transparent;
  transition: all var(--transition);
  white-space: nowrap;
}

.study-tab:hover { color: var(--text); }
.study-tab.active { color: var(--primary); border-bottom-color: var(--primary); }

/* ===== TAB CONTENT ===== */
.study-content {
  flex: 1;
  position: relative;
}

.tab-content {
  display: none;
  padding: 32px 24px;
  animation: fadeIn 0.25s ease;
}

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

/* ===== TOAST ===== */
#toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 10000;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toast {
  padding: 12px 20px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  color: var(--text);
  box-shadow: var(--shadow);
  animation: toastIn 0.3s ease;
  max-width: 360px;
}

.toast.success { border-left: 3px solid var(--correct); }
.toast.error { border-left: 3px solid var(--wrong); }
.toast.info { border-left: 3px solid var(--secondary); }

.toast.removing { animation: toastOut 0.3s ease forwards; }

@keyframes toastIn { from { opacity: 0; transform: translateX(40px); } to { opacity: 1; transform: translateX(0); } }
@keyframes toastOut { to { opacity: 0; transform: translateX(40px); } }

/* ===== CONFETTI ===== */
#confetti-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 9999;
  overflow: hidden;
}

.confetti-piece {
  position: absolute;
  width: 10px;
  height: 10px;
  top: -10px;
  animation: confettiFall 3s ease-out forwards;
}

@keyframes confettiFall {
  0% { transform: translateY(0) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

/* ===== SHARE BUTTON ===== */
.btn-share {
  padding: 8px 16px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 600;
  transition: all var(--transition);
}

.btn-share:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--primary-glow);
}

/* ===== SHARE MODAL ===== */
.share-modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(15, 17, 23, 0.85);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 5000;
  display: flex;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.2s ease;
}

.share-modal {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  width: 90%;
  max-width: 480px;
  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.5);
  animation: fadeSlideUp 0.3s ease;
}

.share-modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 24px 16px;
  border-bottom: 1px solid var(--border);
}

.share-modal-header h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 700;
}

.share-modal-body {
  padding: 24px;
}

.share-loading {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 20px 0;
  color: var(--text-muted);
  font-size: 0.92rem;
}

.share-label {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.share-link-row {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
}

.share-link-input {
  flex: 1;
  padding: 10px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text);
  cursor: text;
  min-width: 0;
}

.btn-copy {
  padding: 10px 18px;
  background: var(--primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 600;
  white-space: nowrap;
  transition: all var(--transition);
  flex-shrink: 0;
}

.btn-copy:hover { background: var(--primary-hover); }

.btn-copy.copied {
  background: var(--correct);
}

.share-buttons {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
}

.share-social-btn {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  font-weight: 600;
  color: #fff;
  transition: all var(--transition);
}

.share-social-btn:hover { transform: translateY(-1px); }

.share-social-btn.whatsapp { background: #25d366; }
.share-social-btn.whatsapp:hover { box-shadow: 0 4px 12px rgba(37, 211, 102, 0.3); }

.share-social-btn.discord { background: #5865f2; }
.share-social-btn.discord:hover { box-shadow: 0 4px 12px rgba(88, 101, 242, 0.3); }

.share-expires {
  font-size: 0.78rem;
  color: var(--text-muted);
  text-align: center;
}

/* ===== SHARE LOAD OVERLAY ===== */
.share-load-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg);
  z-index: 6000;
  display: flex;
  align-items: center;
  justify-content: center;
}

.share-load-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  color: var(--text-muted);
  font-size: 1rem;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 1024px) {
  .topbar-title { max-width: 250px; }
}

@media (max-width: 768px) {
  #input-view { padding: 24px 16px; }
  .logo-text { font-size: 2rem; }
  .topbar { padding: 10px 16px; }
  .topbar-title { display: none; }
  .study-tabs { padding: 0 16px; }
  .study-tab { padding: 12px 16px; font-size: 0.85rem; }
  .tab-content { padding: 20px 16px; }
}

@media (max-width: 480px) {
  .input-tabs { border-radius: var(--radius); }
  .input-tab { padding: 8px 10px; font-size: 0.8rem; }
  .logo-text { font-size: 1.7rem; }
  #paste-input { min-height: 180px; }
  .btn-generate { padding: 14px 20px; font-size: 0.95rem; }
}