/* ============================================================
   Periodica — Design System v1.0
   Dark-first, mobile-responsive, premium chemistry app
   ============================================================ */

/* ─── Google Fonts ──────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Space+Mono:ital,wght@0,400;0,700;1,400&family=DM+Sans:opsz,wght@9..40,300;9..40,400;9..40,500;9..40,600;9..40,700&family=Orbitron:wght@400;700;900&display=swap');

/* ─── CSS Variables — Dark Theme (default) ──────────────────── */
:root {
  /* Colors */
  --bg-primary: #090d1a;
  --bg-secondary: #0e1428;
  --bg-card: #131929;
  --bg-hover: #1a2236;
  --bg-active: #1e2940;
  --border: rgba(255,255,255,0.06);
  --border-active: rgba(108,99,255,0.5);

  --text-primary: #f0f2ff;
  --text-secondary: #8892b0;
  --text-muted: #4a5568;

  --accent: #6c63ff;
  --accent-glow: rgba(108,99,255,0.25);
  --accent-light: #8b85ff;
  --accent-dark: #4d46cc;

  --success: #00d68f;
  --warning: #ffb347;
  --danger: #ff4757;
  --info: #74b9ff;

  /* Typography */
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'Space Mono', monospace;
  --font-display: 'Orbitron', monospace;

  /* Spacing */
  --radius: 12px;
  --radius-sm: 8px;
  --radius-lg: 20px;
  --radius-xl: 28px;

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.5);
  --shadow-accent: 0 0 30px rgba(108,99,255,0.2);

  /* Transitions */
  --transition: 0.2s cubic-bezier(0.4,0,0.2,1);
  --transition-bounce: 0.3s cubic-bezier(0.34,1.56,0.64,1);
}

/* ─── Light Theme ────────────────────────────────────────────── */
[data-theme="light"] {
  --bg-primary: #f4f6fc;
  --bg-secondary: #eef0f8;
  --bg-card: #ffffff;
  --bg-hover: #e8ecf5;
  --bg-active: #dde3f5;
  --border: rgba(0,0,0,0.08);
  --border-active: rgba(108,99,255,0.4);
  --text-primary: #1a1f3a;
  --text-secondary: #4a5580;
  --text-muted: #9199b3;
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.12);
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

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

body.no-scroll { overflow: hidden; }
body.panel-open { overflow: hidden; }

/* ─── Scrollbar ──────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb { background: var(--accent); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent-light); }

/* ─── Typography ─────────────────────────────────────────────── */
h1, h2, h3 { font-weight: 700; line-height: 1.2; }
h1 { font-size: clamp(1.5rem, 4vw, 2.5rem); font-family: var(--font-display); }
h2 { font-size: clamp(1.2rem, 3vw, 1.8rem); }
h3 { font-size: clamp(1rem, 2vw, 1.3rem); }
code { font-family: var(--font-mono); }
a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-light); }

/* ─── Layout ─────────────────────────────────────────────────── */
.app-wrapper { display: flex; flex-direction: column; min-height: 100vh; }

/* ─── Navbar ─────────────────────────────────────────────────── */
.navbar {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; gap: 12px;
  padding: 12px 20px;
  background: rgba(9, 13, 26, 0.92);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}
[data-theme="light"] .navbar { background: rgba(244, 246, 252, 0.92); }

.navbar-brand {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 900;
  color: var(--text-primary);
  letter-spacing: 2px;
  display: flex; align-items: center; gap: 8px;
}
.navbar-brand .brand-icon { font-size: 1.4rem; }
.navbar-brand .brand-sub { font-size: 0.65rem; color: var(--accent); letter-spacing: 3px; display: block; }

.navbar-search {
  flex: 1; max-width: 380px; margin: 0 12px; position: relative;
}
.navbar-search input {
  width: 100%; padding: 9px 16px 9px 40px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 50px;
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 0.9rem;
  outline: none; transition: var(--transition);
}
.navbar-search input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }
.navbar-search input::placeholder { color: var(--text-muted); }
.navbar-search .search-icon { position: absolute; left: 14px; top: 50%; transform: translateY(-50%); color: var(--text-muted); pointer-events: none; }

.search-results {
  position: absolute; top: calc(100% + 8px); left: 0; right: 0;
  background: var(--bg-card);
  border: 1px solid var(--border-active);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  z-index: 200; overflow: hidden;
  display: none; opacity: 0; transform: translateY(-8px);
  transition: var(--transition);
}
.search-results.visible { display: block; opacity: 1; transform: translateY(0); }

.search-result-item {
  display: flex; align-items: center; gap: 12px;
  padding: 10px 16px; cursor: pointer;
  transition: background var(--transition);
}
.search-result-item:hover { background: var(--bg-hover); }
.sr-symbol { font-family: var(--font-display); font-size: 1.2rem; font-weight: 700; min-width: 36px; text-align: center; }
.sr-info { display: flex; flex-direction: column; }
.sr-name { font-weight: 600; font-size: 0.9rem; }
.sr-num { font-size: 0.75rem; color: var(--text-secondary); }
.search-empty { padding: 16px; text-align: center; color: var(--text-muted); }

.navbar-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; }

.user-info { display: flex; align-items: center; gap: 8px; cursor: pointer; }
.user-avatar-sm { width: 32px; height: 32px; border-radius: 50%; border: 2px solid var(--accent); object-fit: cover; }
.xp-mini { font-size: 0.75rem; color: var(--accent); font-weight: 600; white-space: nowrap; }
.streak-mini { font-size: 0.8rem; white-space: nowrap; }

.btn-icon {
  width: 38px; height: 38px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer; font-size: 1rem;
  transition: var(--transition-bounce);
  color: var(--text-primary);
}
.btn-icon:hover { background: var(--bg-hover); border-color: var(--accent); transform: scale(1.08); }

/* ─── XP Bar ─────────────────────────────────────────────────── */
.xp-bar-strip {
  height: 3px; background: var(--bg-secondary);
  overflow: hidden;
}
.xp-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), #ff6b9d, var(--accent));
  background-size: 200% 100%;
  animation: xp-shimmer 2s linear infinite;
  transition: width 0.6s ease;
}
@keyframes xp-shimmer { 0% { background-position: 0% 0%; } 100% { background-position: 200% 0%; } }

/* ─── Tabs ───────────────────────────────────────────────────── */
.tab-nav {
  display: flex; gap: 4px; padding: 8px 20px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  overflow-x: auto; scrollbar-width: none;
}
.tab-nav::-webkit-scrollbar { display: none; }

.tab-btn {
  padding: 8px 18px;
  background: transparent; border: none;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-family: var(--font-body); font-size: 0.88rem; font-weight: 500;
  cursor: pointer; white-space: nowrap;
  transition: var(--transition);
  display: flex; align-items: center; gap: 6px;
}
.tab-btn:hover { color: var(--text-primary); background: var(--bg-hover); }
.tab-btn.active { color: var(--accent); background: var(--accent-glow); font-weight: 600; }
.tab-btn .tab-icon { font-size: 1rem; }

.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* ─── Main Content ───────────────────────────────────────────── */
.main-content { padding: 20px; max-width: 1600px; margin: 0 auto; width: 100%; }

/* ─── Filters Bar ────────────────────────────────────────────── */
.filters-bar {
  display: flex; flex-wrap: wrap; gap: 8px; align-items: center;
  margin-bottom: 16px;
}
.filter-select {
  padding: 7px 12px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-body); font-size: 0.82rem;
  outline: none; cursor: pointer;
  transition: var(--transition);
}
.filter-select:focus { border-color: var(--accent); }
.filter-label { font-size: 0.8rem; color: var(--text-muted); white-space: nowrap; }
.filter-clear-btn {
  padding: 7px 14px;
  background: transparent; border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-secondary); font-size: 0.82rem;
  cursor: pointer; transition: var(--transition);
}
.filter-clear-btn:hover { border-color: var(--danger); color: var(--danger); }

.element-count-badge {
  font-size: 0.8rem; color: var(--text-muted);
  margin-left: auto;
}

/* ─── Category Legend ────────────────────────────────────────── */
.category-legend {
  display: flex; flex-wrap: wrap; gap: 6px;
  margin-bottom: 16px;
}
.legend-item {
  display: flex; align-items: center; gap: 5px;
  font-size: 0.75rem; color: var(--text-secondary);
  cursor: pointer; padding: 4px 8px;
  border-radius: 20px; border: 1px solid transparent;
  transition: var(--transition);
}
.legend-item:hover { border-color: var(--border-active); background: var(--bg-hover); }
.legend-dot { width: 10px; height: 10px; border-radius: 50%; flex-shrink: 0; }

/* ─── Periodic Table Grid ────────────────────────────────────── */
.table-container { overflow-x: auto; padding-bottom: 8px; }

#periodic-table {
  display: grid;
  grid-template-columns: repeat(18, minmax(52px, 1fr));
  grid-template-rows: repeat(10, minmax(58px, 1fr));
  gap: 3px;
  min-width: 960px;
}

.table-cell { position: relative; }
.empty-cell { background: transparent; }

.element-cell {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 5px 4px;
  display: flex; flex-direction: column; align-items: center;
  justify-content: center; text-align: center;
  cursor: pointer;
  position: relative; overflow: hidden;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  border-bottom: 3px solid var(--el-color, #444);
}

.element-cell::before {
  content: ''; position: absolute; inset: 0;
  background: linear-gradient(135deg, var(--el-color, #444) 0%, transparent 60%);
  opacity: 0.06;
  transition: opacity var(--transition);
}

.element-cell:hover {
  transform: translateY(-3px) scale(1.06);
  box-shadow: 0 8px 24px rgba(0,0,0,0.4), 0 0 0 1px var(--el-color, #444), 0 0 16px color-mix(in srgb, var(--el-color, #444) 30%, transparent);
  border-color: var(--el-color, #444);
  z-index: 10;
}
.element-cell:hover::before { opacity: 0.15; }

.element-cell.dimmed { opacity: 0.2; cursor: default; }
.element-cell.dimmed:hover { transform: none; box-shadow: none; }

.element-cell:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.el-number { font-size: 0.6rem; color: var(--text-muted); line-height: 1; align-self: flex-start; }
.el-symbol { font-family: var(--font-display); font-size: 1.1rem; font-weight: 700; color: var(--el-color, var(--text-primary)); line-height: 1.1; }
.el-name { font-size: 0.52rem; color: var(--text-secondary); line-height: 1.2; max-width: 100%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.el-mass { font-size: 0.5rem; color: var(--text-muted); }

.period-label { display: flex; align-items: center; justify-content: center; font-size: 0.7rem; color: var(--text-muted); font-weight: 600; }

.series-label {
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  font-size: 0.6rem; color: var(--text-muted);
  border: 1px dashed var(--border); border-radius: var(--radius-sm);
  padding: 4px;
}
.lanthanide-label { border-color: #fd79a844; color: #fd79a8; }
.actinide-label { border-color: #00cec944; color: #00cec9; }

/* ─── Tooltip ────────────────────────────────────────────────── */
#element-tooltip {
  position: fixed; z-index: 500;
  background: var(--bg-card);
  border: 1px solid var(--border-active);
  border-radius: var(--radius);
  padding: 0; min-width: 220px; max-width: 280px;
  box-shadow: var(--shadow-lg), var(--shadow-accent);
  pointer-events: none; display: none; opacity: 0;
  transition: opacity 0.15s ease;
}
#element-tooltip.visible { opacity: 1; }

.tooltip-header {
  display: flex; align-items: center; gap: 10px; padding: 12px 14px;
  border-bottom: 2px solid var(--border);
  border-left: 4px solid currentColor;
}
.tt-number { font-size: 0.7rem; color: var(--text-muted); min-width: 18px; }
.tt-main { flex: 1; }
.tt-symbol { font-family: var(--font-display); font-size: 1.6rem; font-weight: 900; line-height: 1; display: block; }
.tt-name { font-size: 0.8rem; color: var(--text-secondary); }
.tt-mass { font-size: 0.7rem; color: var(--text-muted); }
.tooltip-body { padding: 10px 14px; display: flex; flex-direction: column; gap: 5px; }
.tt-row { font-size: 0.78rem; color: var(--text-secondary); display: flex; justify-content: space-between; gap: 8px; }
.tt-row span:last-child { color: var(--text-primary); font-weight: 500; text-align: right; }
.tooltip-fact { padding: 8px 14px; border-top: 1px solid var(--border); font-size: 0.72rem; color: var(--text-muted); font-style: italic; line-height: 1.4; }

/* ─── Element Detail Panel ───────────────────────────────────── */
#element-panel {
  position: fixed; inset: 0; z-index: 300;
  display: grid; grid-template-columns: 1fr;
  transform: translateX(100%);
  transition: transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}
#element-panel.active { transform: translateX(0); }

.panel-overlay {
  position: fixed; inset: 0; background: rgba(0,0,0,0.7);
  backdrop-filter: blur(4px); z-index: -1;
}

.panel-inner {
  background: var(--bg-primary);
  margin-left: auto;
  width: min(100vw, 700px);
  height: 100vh;
  overflow-y: auto;
  position: relative;
}

.panel-header {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 12px;
  padding: 14px 20px;
  background: rgba(9, 13, 26, 0.96);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
}
[data-theme="light"] .panel-header { background: rgba(244, 246, 252, 0.96); }

.panel-close {
  width: 36px; height: 36px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: 50%; display: flex; align-items: center; justify-content: center;
  cursor: pointer; font-size: 1rem; color: var(--text-secondary);
  transition: var(--transition);
}
.panel-close:hover { background: var(--bg-hover); color: var(--danger); transform: rotate(90deg); }

.panel-nav-btns { display: flex; gap: 8px; margin-left: auto; }
#save-element-btn {
  padding: 7px 14px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: 50px; font-size: 0.85rem; cursor: pointer;
  transition: var(--transition); color: var(--text-primary);
}
#save-element-btn:hover, #save-element-btn.saved { border-color: var(--danger); color: var(--danger); }

#element-detail-content { padding: 0 0 40px; }

/* Detail Hero */
.detail-hero {
  padding: 24px 24px 20px;
  background: linear-gradient(135deg, var(--bg-card) 0%, color-mix(in srgb, var(--el-color,#6c63ff) 8%, var(--bg-card)) 100%);
  border-bottom: 1px solid var(--border);
}
.detail-hero-main { display: flex; align-items: flex-start; gap: 16px; margin-bottom: 16px; }
.detail-number { font-size: 0.85rem; color: var(--text-muted); font-family: var(--font-mono); }
.detail-symbol-wrap { flex: 1; }
.detail-symbol {
  font-family: var(--font-display); font-size: 3.5rem; font-weight: 900;
  color: var(--el-color, var(--accent));
  line-height: 1; text-shadow: 0 0 30px color-mix(in srgb, var(--el-color, var(--accent)) 50%, transparent);
}
.detail-name { font-size: 1.1rem; font-weight: 600; margin-top: 4px; }
.detail-mass { font-size: 0.85rem; color: var(--text-muted); font-family: var(--font-mono); }
.detail-cat-badge {
  padding: 5px 12px;
  border-radius: 50px; font-size: 0.78rem; font-weight: 600;
  border: 1px solid; white-space: nowrap;
}
.detail-meta-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.meta-chip {
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 8px 10px;
  display: flex; flex-direction: column; align-items: center;
}
.meta-chip span { font-size: 0.65rem; color: var(--text-muted); }
.meta-chip strong { font-size: 0.9rem; font-weight: 700; }

/* Detail Sections */
.detail-section { padding: 20px 24px; border-bottom: 1px solid var(--border); }
.detail-section h3 { font-size: 1rem; margin-bottom: 14px; display: flex; align-items: center; gap: 8px; }

/* Atom Viewer */
.atom-viewer {
  position: relative;
  width: 100%; height: 280px;
  background: radial-gradient(ellipse at center, #0d1530 0%, var(--bg-primary) 70%);
  border-radius: var(--radius);
  overflow: hidden; border: 1px solid var(--border);
}
.atom-viewer canvas { width: 100% !important; height: 100% !important; }
.atom-controls {
  position: absolute; bottom: 10px; right: 10px;
  display: flex; gap: 6px;
}
.atom-controls button {
  width: 32px; height: 32px;
  background: rgba(0,0,0,0.5); border: 1px solid var(--border);
  border-radius: 50%; color: var(--text-secondary); font-size: 0.9rem;
  cursor: pointer; display: flex; align-items: center; justify-content: center;
  transition: var(--transition); backdrop-filter: blur(4px);
}
.atom-controls button:hover { background: var(--accent); color: white; border-color: var(--accent); }
.atom-info-overlay {
  position: absolute; bottom: 10px; left: 10px;
  font-size: 0.7rem; color: var(--text-muted);
  background: rgba(0,0,0,0.5); backdrop-filter: blur(4px);
  padding: 4px 10px; border-radius: 20px;
}
.atom-viewer.fullscreen-atom {
  position: fixed; inset: 0; z-index: 1000;
  width: 100vw; height: 100vh;
  border-radius: 0;
}

/* EC Visual */
.ec-text { margin-bottom: 10px; }
.ec-text code { background: var(--bg-hover); padding: 4px 10px; border-radius: 6px; font-size: 0.9rem; }
.ec-visual { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
.ec-shell {
  display: flex; flex-direction: column; align-items: center; gap: 6px;
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 10px 12px; min-width: 65px;
}
.ec-shell-num { font-size: 0.7rem; color: var(--text-muted); font-family: var(--font-mono); }
.ec-dots { display: flex; flex-wrap: wrap; gap: 4px; justify-content: center; max-width: 80px; }
.ec-dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--accent);
  animation: dot-pop 0.4s both;
  box-shadow: 0 0 6px var(--accent-glow);
}
@keyframes dot-pop { from { transform: scale(0); opacity: 0; } to { transform: scale(1); opacity: 1; } }
.ec-count { font-size: 0.65rem; color: var(--text-muted); }

.valency-row { display: flex; gap: 10px; margin-top: 14px; flex-wrap: wrap; }
.info-pill {
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: 50px; padding: 6px 14px;
  display: flex; gap: 8px; align-items: center; font-size: 0.82rem;
}
.info-pill span { color: var(--text-muted); }
.info-pill strong { color: var(--text-primary); }

/* Props Grid */
.prop-desc { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.7; margin-bottom: 14px; }
.props-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 8px; }
.prop-card {
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 10px 12px;
  display: flex; flex-direction: column; gap: 4px;
}
.prop-card span { font-size: 0.7rem; color: var(--text-muted); }
.prop-card strong { font-size: 0.9rem; font-weight: 600; font-family: var(--font-mono); }

/* Uses */
.uses-list { display: flex; flex-wrap: wrap; gap: 8px; }
.use-tag {
  background: var(--accent-glow); border: 1px solid var(--accent-dark);
  border-radius: 50px; padding: 5px 12px;
  font-size: 0.82rem; color: var(--accent-light);
}

/* Discovery */
.discovery-card { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.disc-item { display: flex; flex-direction: column; gap: 4px; }
.disc-item span { font-size: 0.72rem; color: var(--text-muted); }
.disc-item strong { font-size: 0.9rem; }

/* Isotopes */
.isotopes-table { border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
.iso-header, .iso-row { display: grid; grid-template-columns: 2fr 1fr 1.5fr 1.5fr; gap: 10px; padding: 8px 14px; font-size: 0.8rem; }
.iso-header { background: var(--bg-hover); color: var(--text-muted); font-weight: 600; border-bottom: 1px solid var(--border); }
.iso-row { border-bottom: 1px solid var(--border); }
.iso-row:last-child { border-bottom: none; }
.stable { color: var(--success); }
.unstable { color: var(--warning); }

/* Fun Facts */
.fun-facts-section .fun-fact {
  display: flex; gap: 12px; align-items: flex-start;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
  animation: fact-in 0.3s both;
}
@keyframes fact-in { from { opacity: 0; transform: translateX(-10px); } to { opacity: 1; transform: none; } }
.fun-fact:last-child { border-bottom: none; }
.fact-num {
  min-width: 24px; height: 24px;
  background: var(--accent-glow); border: 1px solid var(--accent-dark);
  border-radius: 50%; display: flex; align-items: center; justify-content: center;
  font-size: 0.7rem; font-weight: 700; color: var(--accent);
}

/* Notes */
.note-textarea {
  width: 100%; min-height: 120px;
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 12px 14px;
  color: var(--text-primary); font-family: var(--font-body); font-size: 0.9rem;
  outline: none; resize: vertical; line-height: 1.6;
  transition: var(--transition);
}
.note-textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }
.notes-actions {
  display: flex; gap: 8px; align-items: center; margin-top: 10px;
}
#note-char-count { font-size: 0.75rem; color: var(--text-muted); margin-right: auto; }

/* Voice/AI buttons */
.btn-voice, .btn-ai {
  padding: 10px 20px;
  border-radius: 50px; font-size: 0.9rem; font-weight: 600;
  cursor: pointer; transition: var(--transition);
  margin-right: 8px; margin-top: 0;
}
.btn-voice { background: transparent; border: 1px solid var(--border); color: var(--text-primary); }
.btn-voice:hover { border-color: var(--info); color: var(--info); }
.btn-ai { background: linear-gradient(135deg, #6c63ff, #a855f7); border: none; color: white; }
.btn-ai:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(108,99,255,0.4); }

/* ─── Buttons ────────────────────────────────────────────────── */
.btn-primary {
  padding: 10px 22px;
  background: var(--accent); border: none;
  border-radius: 50px; color: white;
  font-family: var(--font-body); font-size: 0.9rem; font-weight: 600;
  cursor: pointer; transition: var(--transition-bounce);
}
.btn-primary:hover { background: var(--accent-light); transform: translateY(-2px); box-shadow: 0 6px 20px var(--accent-glow); }

.btn-secondary {
  padding: 10px 22px;
  background: transparent; border: 1px solid var(--accent);
  border-radius: 50px; color: var(--accent);
  font-family: var(--font-body); font-size: 0.9rem; font-weight: 600;
  cursor: pointer; transition: var(--transition);
}
.btn-secondary:hover { background: var(--accent-glow); }

.btn-ghost {
  padding: 10px 22px;
  background: transparent; border: 1px solid var(--border);
  border-radius: 50px; color: var(--text-secondary);
  font-family: var(--font-body); font-size: 0.9rem;
  cursor: pointer; transition: var(--transition);
}
.btn-ghost:hover { color: var(--text-primary); border-color: var(--text-secondary); }

/* ─── Quiz Styles ────────────────────────────────────────────── */
.quiz-landing { padding: 24px 0; max-width: 900px; margin: 0 auto; }
.quiz-header { text-align: center; margin-bottom: 28px; }
.quiz-header p { color: var(--text-secondary); margin-top: 6px; }

.quiz-modes-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 16px; }
.quiz-mode-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 20px;
  transition: var(--transition-bounce); cursor: pointer;
  position: relative; overflow: hidden;
  display: flex; flex-direction: column; gap: 8px;
}
.quiz-mode-card:hover { border-color: var(--accent); transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.quiz-mode-card.featured { border-color: var(--warning); background: linear-gradient(135deg, var(--bg-card), rgba(255,179,71,0.06)); }
.qm-badge { position: absolute; top: 12px; right: 12px; background: var(--warning); color: #000; font-size: 0.65rem; font-weight: 800; padding: 3px 8px; border-radius: 20px; }
.qm-icon { font-size: 2rem; }
.quiz-mode-card h3 { font-size: 1rem; }
.quiz-mode-card p { font-size: 0.82rem; color: var(--text-secondary); flex: 1; }
.qm-meta { display: flex; gap: 6px; flex-wrap: wrap; }
.qm-meta span { font-size: 0.72rem; background: var(--bg-hover); padding: 3px 8px; border-radius: 20px; color: var(--text-muted); }
.qm-xp { color: var(--warning) !important; background: rgba(255,179,71,0.1) !important; }

.btn-quiz-start {
  padding: 8px 16px; background: var(--accent); border: none;
  border-radius: 50px; color: white; font-size: 0.82rem; font-weight: 600;
  cursor: pointer; transition: var(--transition); margin-top: auto;
}
.btn-quiz-start:hover { background: var(--accent-light); }
.premium-btn { background: linear-gradient(135deg, #ff9f43, #ff6b9d); }

.quiz-stats-row { display: flex; gap: 16px; flex-wrap: wrap; margin-top: 24px; justify-content: center; }
.qs-stat { text-align: center; }
.qs-stat span { display: block; font-size: 0.75rem; color: var(--text-muted); }
.qs-stat strong { display: block; font-size: 1.4rem; font-weight: 700; color: var(--accent); }
.login-prompt { text-align: center; color: var(--text-muted); font-size: 0.9rem; padding: 16px; }

/* Active Quiz */
.quiz-active { max-width: 700px; margin: 0 auto; padding: 16px; }
.quiz-top-bar { display: flex; align-items: center; gap: 12px; margin-bottom: 16px; }
.quiz-exit-btn { background: transparent; border: 1px solid var(--border); padding: 6px 12px; border-radius: 50px; color: var(--text-muted); font-size: 0.8rem; cursor: pointer; }
.quiz-progress-wrap { flex: 1; display: flex; flex-direction: column; gap: 4px; }
.quiz-progress-bar { height: 6px; background: var(--bg-card); border-radius: 3px; overflow: hidden; }
.quiz-progress-fill { height: 100%; background: linear-gradient(90deg, var(--accent), #ff6b9d); transition: width 0.4s ease; border-radius: 3px; }
.quiz-counter { font-size: 0.75rem; color: var(--text-muted); text-align: right; }
.quiz-score-display { display: flex; gap: 8px; align-items: center; }
.qs-score, .qs-streak { font-size: 0.85rem; font-weight: 700; white-space: nowrap; }
.qs-streak { color: #ff9f43; }

.quiz-timer-wrap { display: flex; justify-content: center; gap: 16px; align-items: center; margin-bottom: 16px; }
.quiz-timer { position: relative; width: 60px; height: 60px; }
.timer-circle { transform: rotate(-90deg); }
.timer-bg { fill: none; stroke: var(--bg-hover); stroke-width: 3; }
.timer-fill { fill: none; stroke: var(--accent); stroke-width: 3; stroke-linecap: round; transition: stroke-dasharray 1s linear, stroke 0.3s; }
#timer-text { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; font-family: var(--font-display); font-size: 1.1rem; font-weight: 700; }
.timer-warning #timer-text { color: var(--warning); }
.timer-critical #timer-text { color: var(--danger); animation: timer-pulse 0.5s infinite; }
@keyframes timer-pulse { 0%, 100% { transform: scale(1); } 50% { transform: scale(1.2); } }
.difficulty-badge { padding: 4px 12px; border-radius: 20px; font-size: 0.75rem; font-weight: 600; }
.diff-easy { background: rgba(0,214,143,0.15); color: var(--success); }
.diff-medium { background: rgba(255,179,71,0.15); color: var(--warning); }
.diff-hard { background: rgba(255,71,87,0.15); color: var(--danger); }

.quiz-question-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 24px;
  margin-bottom: 16px;
}
.question-text { font-size: 1.05rem; font-weight: 600; margin-bottom: 20px; line-height: 1.5; }
.quiz-options { display: flex; flex-direction: column; gap: 10px; }
.quiz-option {
  display: flex; align-items: center; gap: 14px;
  padding: 12px 16px;
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); cursor: pointer;
  font-family: var(--font-body); font-size: 0.9rem; text-align: left;
  color: var(--text-primary); transition: var(--transition);
}
.quiz-option:hover:not(:disabled) { border-color: var(--accent); background: var(--bg-active); }
.quiz-option:disabled { cursor: default; }
.opt-letter {
  width: 28px; height: 28px; border-radius: 50%;
  background: var(--bg-card); border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-size: 0.75rem; font-weight: 700; flex-shrink: 0;
}
.quiz-option.correct { border-color: var(--success); background: rgba(0,214,143,0.1); }
.quiz-option.correct .opt-letter { background: var(--success); color: white; border-color: var(--success); }
.quiz-option.wrong { border-color: var(--danger); background: rgba(255,71,87,0.1); }
.quiz-option.wrong .opt-letter { background: var(--danger); color: white; border-color: var(--danger); }

/* Assertion */
.assertion-block { display: flex; flex-direction: column; gap: 12px; margin-bottom: 20px; }
.statement { background: var(--bg-hover); border-left: 3px solid var(--accent); padding: 12px 16px; border-radius: 0 var(--radius-sm) var(--radius-sm) 0; }
.statement.reason { border-left-color: var(--info); }
.stmt-label { font-weight: 700; font-size: 0.82rem; display: block; margin-bottom: 4px; color: var(--accent); }
.statement.reason .stmt-label { color: var(--info); }
.ar-option { font-size: 0.82rem; }

/* Guess */
.guess-clues { display: flex; flex-direction: column; gap: 8px; margin-bottom: 16px; }
.guess-clue { display: flex; gap: 10px; align-items: center; font-size: 0.9rem; }
.clue-num { width: 22px; height: 22px; background: var(--accent-glow); border-radius: 50%; display: flex; align-items: center; justify-content: center; font-size: 0.7rem; font-weight: 700; color: var(--accent); flex-shrink: 0; }
.guess-prompt { font-size: 1.1rem; font-weight: 700; text-align: center; margin-top: 8px; }
.guess-input-wrap { display: flex; gap: 8px; margin-top: 10px; }
.guess-text-input {
  flex: 1; padding: 10px 14px;
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); color: var(--text-primary);
  font-family: var(--font-body); outline: none;
  transition: var(--transition);
}
.guess-text-input:focus { border-color: var(--accent); }
.btn-guess-submit { padding: 10px 16px; background: var(--accent); border: none; border-radius: var(--radius-sm); color: white; cursor: pointer; font-weight: 600; }

/* Quiz Actions */
.quiz-actions { display: flex; flex-direction: column; gap: 12px; }
.explanation-card {
  display: flex; gap: 12px; align-items: flex-start;
  padding: 14px 16px;
  border-radius: var(--radius-sm); border: 1px solid;
}
.explanation-card.correct { background: rgba(0,214,143,0.08); border-color: rgba(0,214,143,0.3); }
.explanation-card.wrong { background: rgba(255,71,87,0.08); border-color: rgba(255,71,87,0.3); }
.exp-icon { font-size: 1.4rem; }
.exp-text strong { display: block; margin-bottom: 4px; }
.exp-text p { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.6; }
.btn-quiz-next { padding: 12px 28px; background: var(--accent); border: none; border-radius: 50px; color: white; font-size: 0.95rem; font-weight: 700; cursor: pointer; transition: var(--transition-bounce); align-self: flex-end; }
.btn-quiz-next:hover { background: var(--accent-light); transform: translateY(-2px); }

/* Quiz Results */
.quiz-results { max-width: 600px; margin: 0 auto; padding: 24px; }
.results-hero { padding: 24px; border-radius: var(--radius-lg); text-align: center; margin-bottom: 24px; border: 1px solid var(--border); }
.grade-s { background: linear-gradient(135deg, rgba(255,215,0,0.1), rgba(255,215,0,0.05)); border-color: rgba(255,215,0,0.3) !important; }
.grade-a { background: linear-gradient(135deg, rgba(0,214,143,0.1), rgba(0,214,143,0.05)); border-color: rgba(0,214,143,0.3) !important; }
.grade-b { background: linear-gradient(135deg, rgba(108,99,255,0.1), rgba(108,99,255,0.05)); }
.grade-c { background: linear-gradient(135deg, rgba(255,179,71,0.1), rgba(255,179,71,0.05)); border-color: rgba(255,179,71,0.3) !important; }
.results-grade { font-size: 1.4rem; font-weight: 700; margin-bottom: 16px; }
.results-score-ring { width: 100px; height: 100px; margin: 0 auto 16px; position: relative; }
.score-ring-svg { transform: rotate(-90deg); }
.ring-bg { fill: none; stroke: var(--bg-hover); stroke-width: 3; }
.ring-fill { fill: none; stroke: var(--accent); stroke-width: 3; stroke-linecap: round; }
.ring-pct { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; font-family: var(--font-display); font-size: 1.4rem; font-weight: 900; }
.results-summary { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; text-align: left; margin-top: 16px; }
.rs-item { background: var(--bg-hover); padding: 10px 14px; border-radius: var(--radius-sm); }
.rs-item span { display: block; font-size: 0.75rem; color: var(--text-muted); }
.rs-item strong { font-size: 1rem; font-weight: 700; }
.xp-gained strong { color: var(--warning); }

.results-review { margin-bottom: 24px; }
.results-review h3 { margin-bottom: 12px; }
.review-item { display: flex; gap: 12px; align-items: flex-start; padding: 10px 0; border-bottom: 1px solid var(--border); }
.review-item:last-child { border-bottom: none; }
.ri-icon { font-size: 1rem; margin-top: 2px; }
.ri-content { flex: 1; }
.ri-q { font-size: 0.85rem; margin-bottom: 4px; }
.ri-answer { font-size: 0.8rem; display: flex; gap: 8px; }
.ri-wrong { color: var(--danger); text-decoration: line-through; }
.ri-correct { color: var(--success); }

.results-actions { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; }

/* ─── Flashcard Styles ───────────────────────────────────────── */
.flashcard-dashboard { padding: 24px; max-width: 800px; margin: 0 auto; }
.fc-header { text-align: center; margin-bottom: 24px; }
.fc-stats-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-bottom: 16px; }
.fc-stat { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px; text-align: center; }
.fc-stat.due { border-color: var(--accent); }
.fc-stat-val { display: block; font-size: 1.6rem; font-weight: 700; font-family: var(--font-display); color: var(--accent); }
.fc-stat-label { font-size: 0.75rem; color: var(--text-muted); }
.fc-progress-bar-wrap { margin-bottom: 24px; }
.fc-progress-bar { height: 8px; background: var(--bg-card); border-radius: 4px; overflow: hidden; }
.fc-progress-fill { height: 100%; background: linear-gradient(90deg, var(--accent), #ff6b9d); transition: width 0.6s ease; }

.fc-modes { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 12px; margin-bottom: 24px; }
.fc-mode-btn {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px;
  cursor: pointer; text-align: center;
  transition: var(--transition-bounce); color: var(--text-primary);
  display: flex; flex-direction: column; align-items: center; gap: 6px;
}
.fc-mode-btn:hover:not(:disabled) { border-color: var(--accent); transform: translateY(-3px); }
.fc-mode-btn:disabled { opacity: 0.4; cursor: default; }
.fc-mode-btn.primary { border-color: var(--accent); background: var(--accent-glow); }
.fcm-icon { font-size: 1.8rem; }
.fcm-title { font-weight: 600; font-size: 0.9rem; }
.fcm-count { font-size: 0.75rem; color: var(--text-muted); }

.fc-category-progress { }
.fc-category-progress h4 { margin-bottom: 12px; }
.fc-cat-row { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.fc-cat-name { min-width: 130px; font-size: 0.8rem; font-weight: 600; }
.fc-cat-bar { flex: 1; height: 6px; background: var(--bg-hover); border-radius: 3px; overflow: hidden; }
.fc-cat-fill { height: 100%; border-radius: 3px; transition: width 0.6s ease; }
.fc-cat-pct { font-size: 0.75rem; color: var(--text-muted); min-width: 40px; text-align: right; }

/* Flashcard Session */
.flashcard-session { padding: 20px; max-width: 600px; margin: 0 auto; }
.fc-session-bar { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; }
.fc-session-bar button { background: transparent; border: 1px solid var(--border); padding: 6px 12px; border-radius: 50px; color: var(--text-muted); font-size: 0.8rem; cursor: pointer; }
.fc-session-progress { flex: 1; height: 6px; background: var(--bg-card); border-radius: 3px; overflow: hidden; }
.fc-session-bar-fill { height: 100%; background: var(--accent); transition: width 0.4s ease; }
.fc-session-bar span { font-size: 0.8rem; color: var(--text-muted); }

.fc-scene {
  perspective: 1000px;
  cursor: pointer; margin-bottom: 20px;
  height: 280px;
}
.fc-card {
  position: relative; width: 100%; height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  border-radius: var(--radius-lg);
}
.fc-card.flipped { transform: rotateY(180deg); }
.fc-front, .fc-back {
  position: absolute; inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius-lg);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  padding: 24px;
  border: 1px solid var(--border);
}
.fc-front { background: var(--bg-card); }
.fc-back {
  background: linear-gradient(135deg, color-mix(in srgb, var(--card-color,#6c63ff) 15%, var(--bg-card)), var(--bg-card));
  border-color: color-mix(in srgb, var(--card-color,#6c63ff) 40%, transparent);
  transform: rotateY(180deg);
}
.fc-hint { font-size: 0.75rem; color: var(--text-muted); margin-bottom: 12px; }
.fc-symbol { font-family: var(--font-display); font-size: 5rem; font-weight: 900; line-height: 1; }
.fc-tap-hint { font-size: 0.75rem; color: var(--text-muted); margin-top: 16px; animation: hint-pulse 2s infinite; }
@keyframes hint-pulse { 0%,100% { opacity: 0.5; } 50% { opacity: 1; } }
.fcb-number { font-size: 0.8rem; color: var(--text-muted); }
.fcb-name { font-family: var(--font-display); font-size: 2rem; font-weight: 700; color: var(--card-color, var(--accent)); margin: 6px 0; }
.fcb-config { font-family: var(--font-mono); font-size: 0.8rem; color: var(--text-secondary); }
.fcb-category { background: color-mix(in srgb, var(--card-color,#6c63ff) 20%, transparent); padding: 4px 12px; border-radius: 20px; font-size: 0.78rem; margin-top: 8px; }
.fcb-fact { font-size: 0.75rem; color: var(--text-muted); font-style: italic; text-align: center; margin-top: 10px; line-height: 1.4; }

.fc-rating { text-align: center; }
.fc-rating p { font-size: 0.85rem; color: var(--text-muted); margin-bottom: 12px; }
.fc-rating-btns { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.fc-rate-btn {
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  padding: 10px 8px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); cursor: pointer;
  transition: var(--transition-bounce); color: var(--text-primary);
}
.fc-rate-btn span:first-child { font-size: 1.4rem; }
.fc-rate-btn span:nth-child(2) { font-size: 0.8rem; font-weight: 600; }
.fc-rate-btn small { font-size: 0.65rem; color: var(--text-muted); }
.r-again:hover { border-color: var(--danger); transform: translateY(-3px); }
.r-hard:hover { border-color: var(--warning); transform: translateY(-3px); }
.r-good:hover { border-color: var(--success); transform: translateY(-3px); }
.r-easy:hover { border-color: var(--info); transform: translateY(-3px); }
.fc-keyboard-hints { text-align: center; margin-top: 12px; font-size: 0.72rem; color: var(--text-muted); }
.fc-keyboard-hints span { margin: 0 4px; }

.fc-session-complete { padding: 40px 24px; text-align: center; max-width: 500px; margin: 0 auto; }
.fc-complete-hero { margin-bottom: 24px; }
.fc-complete-icon { font-size: 3rem; margin-bottom: 12px; }
.fc-complete-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-bottom: 20px; }
.fcs-item { background: var(--bg-card); border-radius: var(--radius); padding: 16px; border: 1px solid var(--border); }
.fcs-item.easy { border-color: rgba(0,214,143,0.3); }
.fcs-item.good { border-color: rgba(108,99,255,0.3); }
.fcs-item.again { border-color: rgba(255,71,87,0.3); }
.fcs-count { display: block; font-size: 1.8rem; font-weight: 700; font-family: var(--font-display); }
.fc-xp-gained { font-size: 1.2rem; font-weight: 700; color: var(--warning); margin-bottom: 24px; }
.fc-complete-actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }

/* ─── Dashboard ──────────────────────────────────────────────── */
.stats-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 12px; margin-bottom: 20px; }
.stat-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px; text-align: center;
  transition: var(--transition);
}
.stat-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.stat-value { font-size: 1.8rem; font-weight: 700; font-family: var(--font-display); color: var(--accent); display: block; }
.stat-label { font-size: 0.75rem; color: var(--text-muted); }
.weak-topics { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; }
.weak-topics h4 { margin-bottom: 8px; }
.weak-topics p { font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 10px; }
.topic-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.topic-tag { background: rgba(255,71,87,0.1); border: 1px solid rgba(255,71,87,0.3); color: var(--danger); padding: 4px 10px; border-radius: 20px; font-size: 0.78rem; }

/* ─── Leaderboard ────────────────────────────────────────────── */
.lb-entry {
  display: flex; align-items: center; gap: 12px;
  padding: 12px 16px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); margin-bottom: 8px;
  transition: var(--transition);
}
.lb-entry:hover { border-color: var(--accent); }
.lb-entry.rank-1 { border-color: rgba(255,215,0,0.4); background: linear-gradient(135deg, rgba(255,215,0,0.06), var(--bg-card)); }
.lb-entry.rank-2 { border-color: rgba(192,192,192,0.4); }
.lb-entry.rank-3 { border-color: rgba(205,127,50,0.4); }
.lb-rank { min-width: 28px; font-size: 1.2rem; text-align: center; }
.lb-avatar { width: 36px; height: 36px; border-radius: 50%; }
.lb-info { flex: 1; }
.lb-name { font-weight: 600; font-size: 0.9rem; display: block; }
.lb-meta { font-size: 0.75rem; color: var(--text-muted); }
.lb-xp { font-family: var(--font-display); font-size: 0.9rem; font-weight: 700; color: var(--accent); }

/* ─── Auth Modal ─────────────────────────────────────────────── */
.modal-overlay {
  position: fixed; inset: 0; z-index: 400;
  background: rgba(0,0,0,0.8); backdrop-filter: blur(8px);
  display: flex; align-items: center; justify-content: center;
  opacity: 0; pointer-events: none; transition: var(--transition);
}
.modal-overlay.active { opacity: 1; pointer-events: all; }
.modal-box {
  background: var(--bg-card);
  border: 1px solid var(--border-active);
  border-radius: var(--radius-xl); padding: 32px;
  width: min(440px, 92vw);
  box-shadow: var(--shadow-lg);
  transform: translateY(20px) scale(0.96);
  transition: var(--transition-bounce);
}
.modal-overlay.active .modal-box { transform: translateY(0) scale(1); }
.modal-close { position: absolute; top: 16px; right: 16px; }
.auth-tabs { display: flex; border-bottom: 1px solid var(--border); margin-bottom: 24px; }
.auth-tab { padding: 10px 20px; background: transparent; border: none; color: var(--text-muted); cursor: pointer; font-size: 0.9rem; border-bottom: 2px solid transparent; transition: var(--transition); }
.auth-tab.active { color: var(--accent); border-bottom-color: var(--accent); }
.auth-form { display: flex; flex-direction: column; gap: 14px; }
.form-group label { display: block; font-size: 0.8rem; color: var(--text-secondary); margin-bottom: 6px; }
.form-group input {
  width: 100%; padding: 11px 14px;
  background: var(--bg-hover); border: 1px solid var(--border);
  border-radius: var(--radius-sm); color: var(--text-primary);
  font-family: var(--font-body); outline: none; transition: var(--transition);
}
.form-group input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }
.auth-submit { padding: 12px; background: var(--accent); border: none; border-radius: var(--radius-sm); color: white; font-size: 0.95rem; font-weight: 700; cursor: pointer; transition: var(--transition); }
.auth-submit:hover { background: var(--accent-light); }

/* ─── Toast & Popups ─────────────────────────────────────────── */
#toast-container { position: fixed; bottom: 24px; right: 24px; z-index: 600; display: flex; flex-direction: column; gap: 8px; }
.toast {
  padding: 12px 18px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); font-size: 0.9rem;
  box-shadow: var(--shadow-lg);
  transform: translateX(120%);
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  max-width: 320px;
}
.toast.visible { transform: translateX(0); }
.toast-success { border-color: var(--success); background: linear-gradient(135deg, rgba(0,214,143,0.08), var(--bg-card)); }
.toast-error { border-color: var(--danger); background: linear-gradient(135deg, rgba(255,71,87,0.08), var(--bg-card)); }
.toast-warning { border-color: var(--warning); }
.toast-info { border-color: var(--info); }

.xp-popup {
  position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%) scale(0.8);
  z-index: 700;
  background: linear-gradient(135deg, var(--accent), #ff6b9d);
  color: white; font-family: var(--font-display); font-size: 1.5rem; font-weight: 900;
  padding: 12px 24px; border-radius: 50px;
  pointer-events: none; opacity: 0;
  transition: all 0.3s;
}
.xp-popup.animate { opacity: 1; transform: translate(-50%, -80%) scale(1); }

.achievement-toast {
  position: fixed; bottom: 80px; left: 50%; transform: translateX(-50%) translateY(100px);
  z-index: 700;
  background: linear-gradient(135deg, #1a1f3a, #0d1228);
  border: 1px solid var(--warning);
  border-radius: var(--radius-lg); padding: 16px 20px;
  display: flex; align-items: center; gap: 14px;
  box-shadow: 0 8px 32px rgba(255,179,71,0.3);
  min-width: 280px;
  transition: transform 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
  opacity: 0;
}
.achievement-toast.visible { opacity: 1; transform: translateX(-50%) translateY(0); }
.ach-icon { font-size: 2rem; }
.ach-title { font-size: 0.72rem; color: var(--warning); font-weight: 700; letter-spacing: 1px; }
.ach-name { font-size: 0.95rem; font-weight: 700; }
.ach-desc { font-size: 0.78rem; color: var(--text-muted); }

/* ─── Skeleton Loader ────────────────────────────────────────── */
#skeleton-loader {
  position: fixed; inset: 0; z-index: 999;
  background: var(--bg-primary);
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  transition: opacity 0.4s;
}
#skeleton-loader.hidden { display: none; }
.skeleton-brand { font-family: var(--font-display); font-size: 2rem; font-weight: 900; letter-spacing: 4px; margin-bottom: 24px; }
.skeleton-brand span { background: linear-gradient(90deg, var(--accent), #ff6b9d, var(--accent)); background-size: 200%; -webkit-background-clip: text; -webkit-text-fill-color: transparent; animation: shimmer 2s infinite; }
@keyframes shimmer { 0% { background-position: 0% } 100% { background-position: 200% } }
.skeleton-loading-bar { width: 200px; height: 4px; background: var(--bg-card); border-radius: 2px; overflow: hidden; }
.skeleton-loading-fill { height: 100%; background: linear-gradient(90deg, transparent, var(--accent), transparent); animation: loading-fill 1.5s infinite; }
@keyframes loading-fill { 0% { transform: translateX(-100%); } 100% { transform: translateX(300%); } }
.skeleton-subtitle { margin-top: 12px; font-size: 0.8rem; color: var(--text-muted); }

/* ─── Offline Mode ───────────────────────────────────────────── */
.offline-banner {
  background: rgba(255,71,87,0.1); border-bottom: 1px solid rgba(255,71,87,0.3);
  text-align: center; padding: 6px; font-size: 0.8rem; color: var(--danger);
  display: none;
}
.offline-mode .offline-banner { display: block; }

/* ─── Update Banner ──────────────────────────────────────────── */
#update-banner {
  position: fixed; bottom: 80px; left: 50%; transform: translateX(-50%) translateY(100px);
  z-index: 600; background: var(--bg-card); border: 1px solid var(--accent);
  border-radius: var(--radius); padding: 12px 20px;
  display: flex; gap: 12px; align-items: center;
  box-shadow: var(--shadow-lg);
  transition: transform 0.4s;
  display: none;
}
#update-banner.visible { display: flex; transform: translateX(-50%) translateY(0); }
.update-reload-btn { padding: 6px 14px; background: var(--accent); border: none; border-radius: 50px; color: white; font-size: 0.82rem; cursor: pointer; }

/* ─── Quiz Loading ───────────────────────────────────────────── */
.quiz-loading, .fc-loading {
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  gap: 16px; padding: 80px 20px; color: var(--text-muted);
}
.quiz-spinner {
  width: 40px; height: 40px;
  border: 3px solid var(--bg-hover);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ─── Empty State ────────────────────────────────────────────── */
.empty-state { text-align: center; padding: 60px 20px; color: var(--text-muted); }

/* ─── Footer ─────────────────────────────────────────────────── */
.app-footer {
  margin-top: auto; padding: 16px 24px;
  border-top: 1px solid var(--border);
  display: flex; justify-content: space-between; align-items: center;
  flex-wrap: wrap; gap: 8px;
  font-size: 0.78rem; color: var(--text-muted);
}
.footer-links { display: flex; gap: 16px; }
.footer-links a { color: var(--text-muted); transition: color var(--transition); }
.footer-links a:hover { color: var(--accent); }

/* ─── Responsive ─────────────────────────────────────────────── */
@media (max-width: 768px) {
  .main-content { padding: 12px; }
  
  #periodic-table {
    grid-template-columns: repeat(18, minmax(42px, 1fr));
    grid-template-rows: repeat(10, minmax(48px, 1fr));
    gap: 2px;
    min-width: 760px;
  }
  
  .el-symbol { font-size: 0.9rem; }
  .el-name { display: none; }
  .el-mass { display: none; }
  
  .navbar-search { display: none; }
  
  .panel-inner { width: 100vw; }
  
  .detail-meta-grid { grid-template-columns: repeat(2, 1fr); }
  .props-grid { grid-template-columns: repeat(2, 1fr); }
  .discovery-card { grid-template-columns: 1fr; }
  
  .quiz-modes-grid { grid-template-columns: 1fr 1fr; }
  .fc-stats-row { grid-template-columns: repeat(2, 1fr); }
  .fc-rating-btns { grid-template-columns: repeat(2, 1fr); }
  
  .tab-btn .tab-icon { display: none; }
  .tab-btn { padding: 8px 12px; font-size: 0.82rem; }
}

@media (max-width: 480px) {
  .quiz-modes-grid { grid-template-columns: 1fr; }
  .results-summary { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  #toast-container { left: 12px; right: 12px; }
  .toast { max-width: 100%; }
}

/* ─── Print Styles ───────────────────────────────────────────── */
@media print {
  .navbar, .tab-nav, .app-footer, #skeleton-loader { display: none; }
  #element-panel { position: static; transform: none; }
  .panel-inner { width: 100%; height: auto; overflow: visible; }
}

/* ─── Accessibility ──────────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }