/* ============================================================
   PHYSICSIQ - Motion in One Dimension
   Global Stylesheet v1.0
   Design System: Deep Blue + Yellow + White
   ============================================================ */

/* ---------- CSS Variables ---------- */
:root {
  /* Core Backgrounds */
  --bg-primary: #030712;
  --bg-secondary: #0B1120;
  --bg-card: #111827;
  --bg-card-hover: #1F2937;
  --bg-card-deep: #0B1120;
  
  /* Accents */
  --accent-blue: #3b82f6;
  --accent-green: #10B981;
  --accent-red: #EF4444;
  --accent-purple: #8B5CF6;
  --accent-orange: #F97316;
  --accent-yellow: #FFD700;
  --accent-yellow-dim: #D4AF37;
  --accent-yellow-glow: rgba(255, 215, 0, 0.15);
  
  /* Texts */
  --text-primary: #F9FAFB;
  --text-secondary: #9CA3AF;
  --text-muted: #6B7280;
  
  /* Borders & Shadows */
  --border-color: #374151;
  --border-subtle: rgba(255,255,255,0.05);
  --shadow-card: 0 10px 30px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 24px rgba(59,130,246,0.3);
  
  /* Utils */
  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-xl: 32px;
  --transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  --navbar-height: 72px;
  --font-main: 'Inter', system-ui, sans-serif;
  --font-heading: 'Outfit', 'Inter', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body {
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-main);
  line-height: 1.7;
  min-height: 100vh;
  overflow-x: hidden;
}
a { color: var(--accent-yellow); text-decoration: none; transition: var(--transition); }
a:hover { color: #fff; }
img { max-width: 100%; }
ul { list-style: none; }

/* ---------- Scrollbar ---------- */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb { background: var(--accent-yellow); border-radius: 10px; }

/* ---------- Typography ---------- */
h1,h2,h3,h4,h5,h6 { line-height: 1.3; font-weight: 700; }
h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.2rem); }
h3 { font-size: clamp(1.2rem, 2vw, 1.6rem); }
h4 { font-size: 1.15rem; }
p { color: var(--text-secondary); }
.text-yellow { color: var(--accent-yellow) !important; }
.text-green { color: var(--accent-green) !important; }
.text-red { color: var(--accent-red) !important; }
.text-blue { color: var(--accent-blue) !important; }
.text-purple { color: var(--accent-purple) !important; }
.text-white { color: #fff !important; }

/* ---------- Layout Utilities ---------- */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section { padding: 72px 0; }
.section-sm { padding: 40px 0; }
.flex { display: flex; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.flex-between { display: flex; align-items: center; justify-content: space-between; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.gap-8 { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.gap-20 { gap: 20px; }
.gap-24 { gap: 24px; }
.mt-8 { margin-top: 8px; }
.mt-12 { margin-top: 12px; }
.mt-16 { margin-top: 16px; }
.mt-20 { margin-top: 20px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mt-40 { margin-top: 40px; }
.mb-8 { margin-bottom: 8px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mb-32 { margin-bottom: 32px; }
.text-center { text-align: center; }
.full-width { width: 100%; }

/* ---------- NAVBAR ---------- */
.navbar {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  height: var(--navbar-height);
  background: rgba(7, 12, 31, 0.95);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border-color);
  z-index: 9999;
  display: flex;
  align-items: center;
}
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: 1300px;
  margin: 0 auto;
  padding: 0 24px;
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.25rem;
  font-weight: 800;
  color: #fff;
  letter-spacing: -0.5px;
}
.nav-logo .logo-icon {
  width: 36px; height: 36px;
  background: linear-gradient(135deg, var(--accent-yellow), #ff9f43);
  border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem;
  box-shadow: 0 0 16px rgba(255,215,0,0.3);
}
.nav-logo span.brand { color: var(--accent-yellow); }
.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: nowrap;
}
.nav-links a {
  color: var(--text-secondary);
  font-size: 0.78rem;
  font-weight: 500;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
  white-space: nowrap;
  letter-spacing: 0.2px;
}
.nav-links a:hover, .nav-links a.active {
  color: var(--accent-yellow);
  background: var(--accent-yellow-glow);
}
.nav-right {
  display: flex;
  align-items: center;
  gap: 12px;
}
.exam-badge-mini {
  background: var(--accent-yellow);
  color: #000;
  font-size: 0.7rem;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: 20px;
  letter-spacing: 0.5px;
}
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 6px;
}
.hamburger span {
  width: 22px; height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: var(--transition);
}

/* ---------- EXAM TOGGLE ---------- */
.exam-toggle-bar {
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-subtle);
  padding: 10px 24px;
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  position: sticky;
  top: var(--navbar-height);
  z-index: 999;
}
.exam-toggle-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
}
.exam-toggle-buttons {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.exam-btn {
  padding: 5px 14px;
  border-radius: 20px;
  border: 1.5px solid var(--border-color);
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  letter-spacing: 0.3px;
}
.exam-btn:hover { border-color: var(--accent-yellow); color: var(--accent-yellow); }
.exam-btn.active {
  background: var(--accent-yellow);
  border-color: var(--accent-yellow);
  color: #000;
  box-shadow: 0 0 12px rgba(255,215,0,0.3);
}
.exam-content { display: none; }
.exam-content.active { display: block; }

/* ---------- CARDS ---------- */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}
.card:hover {
  border-color: var(--border-color);
  transform: translateY(-3px);
  box-shadow: var(--shadow-card);
}
.card-yellow-border { border-left: 3px solid var(--accent-yellow); }
.card-green-border { border-left: 3px solid var(--accent-green); }
.card-red-border { border-left: 3px solid var(--accent-red); }
.card-blue-border { border-left: 3px solid var(--accent-blue); }
.card-purple-border { border-left: 3px solid var(--accent-purple); }
.card-icon {
  width: 48px; height: 48px;
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.4rem;
  margin-bottom: 16px;
}
.icon-yellow { background: rgba(255,215,0,0.12); }
.icon-green { background: rgba(0,229,160,0.12); }
.icon-blue { background: rgba(74,143,255,0.12); }
.icon-red { background: rgba(255,77,109,0.12); }
.icon-purple { background: rgba(167,139,250,0.12); }

/* ---------- SIGNATURE BOXES ---------- */
.insight-box, .mistake-box, .thinking-box, .strategy-box, .formula-box, .key-box {
  border-radius: var(--radius-md);
  padding: 18px 20px;
  margin: 20px 0;
  position: relative;
  overflow: hidden;
}
.insight-box {
  background: rgba(74,143,255,0.08);
  border: 1px solid rgba(74,143,255,0.3);
  border-left: 4px solid var(--accent-blue);
}
.mistake-box {
  background: rgba(255,77,109,0.08);
  border: 1px solid rgba(255,77,109,0.3);
  border-left: 4px solid var(--accent-red);
}
.thinking-box {
  background: rgba(167,139,250,0.08);
  border: 1px solid rgba(167,139,250,0.3);
  border-left: 4px solid var(--accent-purple);
}
.strategy-box {
  background: rgba(255,215,0,0.07);
  border: 1px solid rgba(255,215,0,0.3);
  border-left: 4px solid var(--accent-yellow);
}
.formula-box {
  background: var(--bg-card-deep);
  border: 1px solid rgba(255,215,0,0.25);
  border-left: 4px solid var(--accent-yellow);
}
.key-box {
  background: rgba(0,229,160,0.07);
  border: 1px solid rgba(0,229,160,0.25);
  border-left: 4px solid var(--accent-green);
}
.box-header {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 10px;
}
.insight-box .box-header { color: var(--accent-blue); }
.mistake-box .box-header { color: var(--accent-red); }
.thinking-box .box-header { color: var(--accent-purple); }
.strategy-box .box-header { color: var(--accent-yellow); }
.formula-box .box-header { color: var(--accent-yellow); }
.key-box .box-header { color: var(--accent-green); }
.box-content { color: var(--text-secondary); font-size: 0.95rem; line-height: 1.65; }
.box-content strong { color: var(--text-primary); }

/* ---------- SECTION HEADER ---------- */
.section-header { margin-bottom: 48px; }
.section-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--accent-yellow-glow);
  border: 1px solid rgba(255,215,0,0.3);
  color: var(--accent-yellow);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  padding: 5px 14px;
  border-radius: 20px;
  margin-bottom: 16px;
}
.section-title { color: #fff; margin-bottom: 14px; }
.section-title span { color: var(--accent-yellow); }
.section-desc { color: var(--text-secondary); max-width: 620px; font-size: 1.05rem; }

/* ---------- BUTTONS ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  outline: none;
  text-decoration: none;
  white-space: nowrap;
}
.btn-primary {
  background: var(--accent-yellow);
  color: #000;
}
.btn-primary:hover {
  background: #fff;
  color: #000;
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(255,215,0,0.3);
}
.btn-outline {
  background: transparent;
  color: var(--accent-yellow);
  border: 1.5px solid var(--accent-yellow);
}
.btn-outline:hover {
  background: var(--accent-yellow);
  color: #000;
  transform: translateY(-2px);
}
.btn-ghost {
  background: rgba(255,255,255,0.06);
  color: var(--text-primary);
  border: 1px solid var(--border-subtle);
}
.btn-ghost:hover {
  background: rgba(255,255,255,0.1);
  border-color: var(--border-color);
}
.btn-sm { padding: 8px 16px; font-size: 0.82rem; }
.btn-lg { padding: 16px 36px; font-size: 1rem; }

/* ---------- BADGES ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.4px;
}
.badge-yellow { background: rgba(255,215,0,0.15); color: var(--accent-yellow); border: 1px solid rgba(255,215,0,0.3); }
.badge-green { background: rgba(0,229,160,0.12); color: var(--accent-green); border: 1px solid rgba(0,229,160,0.25); }
.badge-red { background: rgba(255,77,109,0.12); color: var(--accent-red); border: 1px solid rgba(255,77,109,0.25); }
.badge-blue { background: rgba(74,143,255,0.12); color: var(--accent-blue); border: 1px solid rgba(74,143,255,0.25); }
.badge-purple { background: rgba(167,139,250,0.12); color: var(--accent-purple); border: 1px solid rgba(167,139,250,0.25); }

/* ---------- TABS ---------- */
/* Pattern A: .tabs-wrapper > .tabs-nav > .tab-btn + sibling .tab-content */
.tabs-wrapper { margin-top: 1.5rem; }
.tabs-nav {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 24px;
  flex-wrap: wrap;
  overflow-x: auto;
  scrollbar-width: none;
}
.tabs-nav::-webkit-scrollbar { display: none; }
.tab-content { display: none; }
.tab-content.active { display: block; animation: fadeIn 0.3s ease; }

/* Pattern B: .tabs-container > .tab-nav > [data-tab] + [data-panel] */
.tab-bar {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 28px;
  flex-wrap: wrap;
}
/* Shared button style for all tab patterns */
.tab-btn {
  padding: 10px 20px;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 0.88rem;
  font-weight: 600;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: var(--transition);
  position: relative;
  bottom: -1px;
  white-space: nowrap;
  font-family: inherit;
}
.tab-btn:hover { color: var(--text-primary); }
.tab-btn.active {
  color: var(--accent-yellow);
  border-bottom-color: var(--accent-yellow);
}
.tab-panel { display: none; }
.tab-panel.active { display: block; animation: fadeIn 0.3s ease; }

/* ---------- ACCORDION ---------- */
.accordion { border: 1px solid var(--border-subtle); border-radius: var(--radius-md); overflow: hidden; }
.accordion + .accordion { margin-top: 10px; }
.accordion-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 22px;
  background: var(--bg-card);
  cursor: pointer;
  transition: var(--transition);
  user-select: none;
  gap: 12px;
  width: 100%;
  border: none;
  color: var(--text-primary);
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  text-align: left;
}
.accordion-header:hover { background: var(--bg-card-hover); }
.accordion-header.open { background: var(--bg-card-hover); }
.accordion-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 10px;
}
.accordion-icon {
  width: 26px; height: 26px;
  background: var(--bg-card-deep);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  color: var(--accent-yellow);
  font-size: 0.75rem;
  transition: var(--transition);
  flex-shrink: 0;
}
.accordion-header.open .accordion-icon { transform: rotate(180deg); }
.accordion-body {
  display: none;
  padding: 20px 22px;
  background: var(--bg-card-deep);
  border-top: 1px solid var(--border-subtle);
}
.accordion-body.open { display: block; animation: slideDown 0.25s ease; }

/* ---------- SOLUTION REVEAL ---------- */
.solution-reveal {
  display: none;
  background: rgba(0,229,160,0.07);
  border: 1px solid rgba(0,229,160,0.25);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  margin-bottom: 12px;
  font-size: 0.9rem;
  color: var(--text-primary);
  line-height: 1.7;
}
.solution-reveal.show { display: block; animation: fadeIn 0.35s ease; }
.solution-reveal strong { color: var(--accent-green); }

/* ---------- PROBLEM CARD ---------- */
.problem-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 20px 22px;
  margin-bottom: 16px;
  transition: var(--transition);
}
.problem-card:hover { border-color: rgba(255,215,0,0.2); }
.problem-header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 14px;
}
.problem-num {
  width: 32px; height: 32px;
  background: var(--gradient-accent);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-weight: 800;
  font-size: 0.88rem;
  color: #fff;
  flex-shrink: 0;
}
.problem-meta { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.problem-text { color: var(--text-primary); font-size: 0.97rem; line-height: 1.65; margin-bottom: 16px; font-weight: 500; }
.problem-options { display: flex; flex-direction: column; gap: 8px; margin-bottom: 16px; }
.option {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  background: var(--bg-card-deep);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.93rem;
  cursor: pointer;
  transition: var(--transition);
}
.option:hover { border-color: rgba(255,215,0,0.3); color: var(--text-primary); }
.option-key {
  font-weight: 800;
  color: var(--accent-yellow);
  font-size: 0.82rem;
  min-width: 18px;
}
/* Exam tags */
.tag-cbse { background: rgba(59,130,246,0.15); color: #93c5fd; font-size: 0.72rem; font-weight: 700; padding: 2px 8px; border-radius: 10px; text-transform: uppercase; letter-spacing: 0.5px; }
.tag-neet { background: rgba(16,185,129,0.15); color: #6ee7b7; font-size: 0.72rem; font-weight: 700; padding: 2px 8px; border-radius: 10px; text-transform: uppercase; letter-spacing: 0.5px; }
.tag-jee  { background: rgba(245,158,11,0.15); color: #fcd34d; font-size: 0.72rem; font-weight: 700; padding: 2px 8px; border-radius: 10px; text-transform: uppercase; letter-spacing: 0.5px; }
.tag-adv  { background: rgba(239,68,68,0.15); color: #fca5a5; font-size: 0.72rem; font-weight: 700; padding: 2px 8px; border-radius: 10px; text-transform: uppercase; letter-spacing: 0.5px; }
.difficulty-easy   { font-size: 0.72rem; font-weight: 700; color: var(--accent-green); }
.difficulty-medium { font-size: 0.72rem; font-weight: 700; color: var(--accent-orange, #f59e0b); }
.difficulty-hard   { font-size: 0.72rem; font-weight: 700; color: var(--accent-red); }

/* ---------- FORMULA TABLE ---------- */
.formula-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}
.formula-table th {
  background: var(--bg-card-deep);
  color: var(--accent-yellow);
  padding: 12px 16px;
  text-align: left;
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  border-bottom: 1px solid var(--border-color);
}
.formula-table td {
  padding: 12px 16px;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border-subtle);
  vertical-align: top;
}
.formula-table tr:last-child td { border-bottom: none; }
.formula-table tr:hover td { background: rgba(255,215,0,0.04); color: var(--text-primary); }
.formula-table .formula-cell {
  font-family: var(--font-mono);
  color: var(--accent-yellow);
  font-weight: 600;
  font-size: 0.98rem;
  background: rgba(255,215,0,0.07);
  padding: 6px 12px;
  border-radius: 6px;
  display: inline-block;
}

/* ---------- MATH DISPLAY ---------- */
.math-display {
  background: var(--bg-card-deep);
  border: 1px solid rgba(255,215,0,0.2);
  border-radius: var(--radius-sm);
  padding: 14px 20px;
  font-family: var(--font-mono);
  font-size: 1.05rem;
  color: var(--accent-yellow);
  text-align: center;
  letter-spacing: 0.5px;
  margin: 12px 0;
}
.math-inline {
  font-family: var(--font-mono);
  color: var(--accent-yellow);
  background: rgba(255,215,0,0.08);
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.95em;
}

/* ---------- GRAPH DIAGRAM ---------- */
.graph-container {
  background: var(--bg-card-deep);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 24px;
  position: relative;
  overflow: hidden;
}
.graph-svg-wrap { width: 100%; height: 220px; }
.graph-title {
  text-align: center;
  color: var(--accent-yellow);
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 16px;
}
.graph-label {
  font-size: 0.78rem;
  fill: var(--text-muted);
}
.graph-axis { stroke: rgba(255,255,255,0.2); stroke-width: 1.5; }
.graph-line-yellow { stroke: #ffd700; stroke-width: 2.5; fill: none; }
.graph-line-blue { stroke: #4a8fff; stroke-width: 2.5; fill: none; }
.graph-line-green { stroke: #00e5a0; stroke-width: 2.5; fill: none; }
.graph-fill-yellow { fill: rgba(255,215,0,0.08); stroke: none; }

/* ---------- PROGRESS TRACKER ---------- */
.progress-tracker {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 20px 24px;
}
.progress-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}
.progress-title { font-size: 0.88rem; font-weight: 600; color: var(--text-primary); }
.progress-pct { font-size: 1.3rem; font-weight: 700; color: var(--accent-yellow); }
.progress-bar-wrap {
  background: rgba(255,255,255,0.07);
  border-radius: 10px;
  height: 8px;
  overflow: hidden;
  margin-bottom: 12px;
}
.progress-bar-fill {
  height: 100%;
  border-radius: 10px;
  background: linear-gradient(90deg, var(--accent-yellow), var(--accent-orange));
  transition: width 0.6s ease;
}
.progress-chapters {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}
.progress-dot {
  width: 10px; height: 10px;
  border-radius: 50%;
  cursor: pointer;
  transition: var(--transition);
}
.progress-dot.done { background: var(--accent-green); }
.progress-dot.current { background: var(--accent-yellow); box-shadow: 0 0 8px rgba(255,215,0,0.4); }
.progress-dot.pending { background: rgba(255,255,255,0.12); }

/* ---------- TIMER ---------- */
.timer-widget {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 18px 24px;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.timer-display {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent-yellow);
  letter-spacing: 2px;
  min-width: 100px;
}
.timer-display.warning { color: var(--accent-red); animation: blink 1s infinite; }
.timer-controls { display: flex; gap: 8px; flex-wrap: wrap; }

/* ---------- FLASHCARD ---------- */
.flashcard-wrap {
  perspective: 1000px;
  width: 100%;
  max-width: 520px;
  height: 220px;
  margin: 0 auto;
  cursor: pointer;
}
.flashcard {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(.4,0,.2,1);
}
.flashcard.flipped { transform: rotateY(180deg); }
.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 24px;
  text-align: center;
}
.flashcard-front {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
}
.flashcard-back {
  background: linear-gradient(135deg, #0d1b4b, #162146);
  border: 1px solid rgba(255,215,0,0.3);
  transform: rotateY(180deg);
}
.flashcard-question { font-size: 1.05rem; font-weight: 600; color: var(--text-primary); }
.flashcard-answer { font-family: var(--font-mono); font-size: 1.1rem; color: var(--accent-yellow); font-weight: 700; }
.flashcard-hint { font-size: 0.78rem; color: var(--text-muted); margin-top: 8px; }
.flashcard-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-top: 20px;
}
.flashcard-counter { color: var(--text-muted); font-size: 0.85rem; }

/* ---------- PRACTICE QUESTIONS ---------- */
.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 24px;
  margin-bottom: 20px;
  transition: var(--transition);
}
.question-card:hover { border-color: var(--border-color); }
.question-header {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  margin-bottom: 16px;
}
.question-num {
  width: 32px; height: 32px;
  background: var(--accent-yellow);
  color: #000;
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  font-weight: 700;
  font-size: 0.85rem;
  flex-shrink: 0;
  margin-top: 2px;
}
.question-text { color: var(--text-primary); font-size: 0.97rem; line-height: 1.65; }
.question-options { display: flex; flex-direction: column; gap: 10px; margin: 16px 0; }
.option-btn {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 12px 16px;
  background: var(--bg-card-deep);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  text-align: left;
  width: 100%;
  color: var(--text-secondary);
  font-size: 0.93rem;
}
.option-btn:hover { border-color: rgba(255,215,0,0.3); color: var(--text-primary); }
.option-btn.selected { border-color: var(--accent-yellow); background: var(--accent-yellow-glow); color: var(--text-primary); }
.option-btn.correct { border-color: var(--accent-green); background: rgba(0,229,160,0.08); color: var(--accent-green); }
.option-btn.wrong { border-color: var(--accent-red); background: rgba(255,77,109,0.08); color: var(--accent-red); }
.option-label {
  font-weight: 700;
  color: var(--accent-yellow);
  font-size: 0.85rem;
  min-width: 18px;
}
.option-btn.correct .option-label { color: var(--accent-green); }
.option-btn.wrong .option-label { color: var(--accent-red); }
.answer-reveal {
  display: none;
  background: var(--bg-card-deep);
  border: 1px solid rgba(0,229,160,0.3);
  border-radius: var(--radius-sm);
  padding: 16px;
  margin-top: 12px;
  animation: fadeIn 0.3s ease;
}
.answer-reveal.visible { display: block; }
.answer-reveal .answer-title {
  color: var(--accent-green);
  font-weight: 700;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 8px;
}
.difficulty-tag {
  font-size: 0.7rem;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 10px;
}
.diff-easy { background: rgba(0,229,160,0.15); color: var(--accent-green); }
.diff-medium { background: rgba(255,159,67,0.15); color: var(--accent-orange); }
.diff-hard { background: rgba(255,77,109,0.15); color: var(--accent-red); }

/* ---------- STEP SOLVER ---------- */
.step-box {
  counter-increment: step;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 16px 20px;
  margin-bottom: 12px;
  position: relative;
}
.step-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px; height: 24px;
  background: var(--accent-yellow);
  color: #000;
  border-radius: 50%;
  font-size: 0.72rem;
  font-weight: 700;
  margin-right: 10px;
  flex-shrink: 0;
}
.step-title { display: flex; align-items: center; font-weight: 600; color: var(--text-primary); margin-bottom: 8px; }
.step-content { color: var(--text-secondary); font-size: 0.93rem; padding-left: 34px; }

/* ---------- STATS CARD ---------- */
.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 22px 24px;
  text-align: center;
  transition: var(--transition);
}
.stat-card:hover { border-color: var(--border-color); transform: translateY(-3px); }
.stat-value {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--accent-yellow);
  line-height: 1;
  margin-bottom: 6px;
}
.stat-label { font-size: 0.82rem; color: var(--text-muted); font-weight: 500; text-transform: uppercase; letter-spacing: 0.8px; }
.stat-sub { font-size: 0.78rem; color: var(--text-muted); margin-top: 4px; }

/* ---------- WEIGHTAGE BAR ---------- */
.weightage-item {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 14px;
}
.weightage-topic {
  font-size: 0.88rem;
  color: var(--text-secondary);
  min-width: 180px;
  flex-shrink: 0;
}
.weightage-bar-wrap {
  flex: 1;
  background: rgba(255,255,255,0.07);
  border-radius: 6px;
  height: 8px;
  overflow: hidden;
}
.weightage-bar-fill {
  height: 100%;
  border-radius: 6px;
  background: linear-gradient(90deg, var(--accent-yellow), var(--accent-orange));
}
.weightage-pct {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent-yellow);
  min-width: 36px;
  text-align: right;
}

/* ---------- CONCEPT MAP ---------- */
.concept-map {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  padding: 20px;
  background: var(--bg-card-deep);
  border-radius: var(--radius-md);
  justify-content: center;
}
.concept-node {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 10px 18px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
  position: relative;
  cursor: default;
  transition: var(--transition);
}
.concept-node.central {
  background: rgba(255,215,0,0.15);
  border-color: var(--accent-yellow);
  color: var(--accent-yellow);
  font-size: 1rem;
  padding: 14px 24px;
}
.concept-node:hover { border-color: var(--accent-yellow); transform: scale(1.04); }
.concept-arrow {
  color: var(--text-muted);
  font-size: 1.2rem;
  align-self: center;
}

/* ---------- SEARCH BOX ---------- */
.search-box {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--bg-card);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 10px 16px;
  transition: var(--transition);
}
.search-box:focus-within {
  border-color: var(--accent-yellow);
  box-shadow: 0 0 0 3px rgba(255,215,0,0.1);
}
.search-box input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--text-primary);
  font-size: 0.93rem;
  font-family: var(--font-main);
}
.search-box input::placeholder { color: var(--text-muted); }
.search-icon { color: var(--text-muted); font-size: 1rem; }

/* ---------- CALCULATOR ---------- */
.calc-container {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 24px;
}
.calc-title {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--accent-yellow);
  margin-bottom: 18px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-bottom: 14px; }
.calc-field label {
  display: block;
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 6px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.calc-field input, .calc-field select {
  width: 100%;
  background: var(--bg-card-deep);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 9px 12px;
  color: var(--text-primary);
  font-size: 0.9rem;
  font-family: var(--font-main);
  outline: none;
  transition: var(--transition);
}
.calc-field input:focus, .calc-field select:focus {
  border-color: var(--accent-yellow);
  box-shadow: 0 0 0 2px rgba(255,215,0,0.1);
}
.calc-field select option { background: var(--bg-card); }
.calc-result {
  background: var(--bg-card-deep);
  border: 1px solid rgba(0,229,160,0.3);
  border-radius: var(--radius-sm);
  padding: 14px 18px;
  margin-top: 14px;
}
.calc-result-label { font-size: 0.75rem; color: var(--text-muted); font-weight: 600; text-transform: uppercase; letter-spacing: 0.8px; margin-bottom: 6px; }
.calc-result-value { font-family: var(--font-mono); font-size: 1.2rem; font-weight: 700; color: var(--accent-green); }

/* ---------- PAGE HERO ---------- */
.page-hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
  border-bottom: 1px solid var(--border-subtle);
  padding: 52px 0 40px;
  position: relative;
  overflow: hidden;
}
.page-hero::before {
  content: '';
  position: absolute;
  top: -80px; right: -80px;
  width: 320px; height: 320px;
  background: radial-gradient(circle, rgba(255,215,0,0.06) 0%, transparent 70%);
  pointer-events: none;
}
.page-hero::after {
  content: '';
  position: absolute;
  bottom: -60px; left: -60px;
  width: 250px; height: 250px;
  background: radial-gradient(circle, rgba(74,143,255,0.05) 0%, transparent 70%);
  pointer-events: none;
}
.hero-breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 16px;
}
.hero-breadcrumb a { color: var(--text-muted); }
.hero-breadcrumb a:hover { color: var(--accent-yellow); }
.hero-breadcrumb .sep { color: var(--text-muted); }
.page-hero h1 { color: #fff; margin-bottom: 14px; }
.page-hero p { color: var(--text-secondary); max-width: 580px; font-size: 1.05rem; }
.hero-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 20px;
  flex-wrap: wrap;
}

/* ---------- DIVIDER ---------- */
.divider {
  height: 1px;
  background: var(--border-subtle);
  margin: 32px 0;
}
.divider-yellow {
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--accent-yellow), transparent);
  margin: 32px 0;
}

/* ---------- TOOLTIP ---------- */
.tooltip-wrap { position: relative; display: inline-block; }
.tooltip-text {
  visibility: hidden;
  opacity: 0;
  background: #1a2550;
  color: #fff;
  font-size: 0.78rem;
  padding: 6px 12px;
  border-radius: 6px;
  position: absolute;
  bottom: calc(100% + 8px);
  left: 50%;
  transform: translateX(-50%);
  white-space: nowrap;
  pointer-events: none;
  transition: opacity 0.2s ease;
  border: 1px solid var(--border-color);
  z-index: 999;
}
.tooltip-wrap:hover .tooltip-text { visibility: visible; opacity: 1; }

/* ---------- FOOTER ---------- */
.site-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-subtle);
  padding: 32px 0;
  margin-top: 60px;
}
.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}
.footer-logo { font-weight: 800; color: var(--accent-yellow); font-size: 1.1rem; }
.footer-links { display: flex; gap: 20px; flex-wrap: wrap; }
.footer-links a { color: var(--text-muted); font-size: 0.82rem; }
.footer-links a:hover { color: var(--accent-yellow); }
.footer-copy { color: var(--text-muted); font-size: 0.78rem; }

/* ---------- ANIMATIONS ---------- */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}
@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.03); }
}
@keyframes shimmer {
  0% { background-position: -200% center; }
  100% { background-position: 200% center; }
}
.animate-in { animation: fadeIn 0.5s ease forwards; }

/* ---------- NOTIFICATION TOAST ---------- */
#toast {
  position: fixed;
  bottom: 28px;
  right: 28px;
  background: var(--bg-card);
  border: 1px solid var(--accent-yellow);
  border-radius: var(--radius-sm);
  padding: 14px 20px;
  color: var(--text-primary);
  font-size: 0.88rem;
  font-weight: 600;
  z-index: 99999;
  transform: translateY(100px);
  opacity: 0;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  gap: 10px;
  max-width: 320px;
  box-shadow: var(--shadow-card);
}
#toast.show { transform: translateY(0); opacity: 1; }

/* ---------- RESPONSIVE ---------- */
@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .nav-links { gap: 2px; }
  .nav-links a { padding: 5px 7px; font-size: 0.72rem; }
}
@media (max-width: 768px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: var(--navbar-height);
    left: 0; right: 0;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-subtle);
    padding: 16px 24px;
    gap: 4px;
    z-index: 9998;
  }
  .hamburger { display: flex; }
  .section { padding: 48px 0; }
  .page-hero { padding: 36px 0 28px; }
  .calc-grid { grid-template-columns: 1fr; }
  .exam-toggle-bar { padding: 8px 16px; }
  .weightage-topic { min-width: 120px; font-size: 0.78rem; }
  .flashcard-wrap { height: 200px; }
  .container { padding: 0 16px; }
}
@media (max-width: 480px) {
  .tab-bar { gap: 2px; }
  .tab-btn { padding: 8px 12px; font-size: 0.8rem; }
}

/* ---------- UTILITY EXTRAS ---------- */
.highlight { background: rgba(255,215,0,0.1); padding: 2px 6px; border-radius: 4px; color: var(--accent-yellow); font-weight: 600; }
.code-inline { font-family: var(--font-mono); background: rgba(255,255,255,0.07); padding: 2px 8px; border-radius: 4px; font-size: 0.88em; color: var(--accent-blue); }
.list-check li, .list-arrow li { display: flex; align-items: flex-start; gap: 10px; margin-bottom: 10px; color: var(--text-secondary); font-size: 0.95rem; }
.list-check li::before { content: '✓'; color: var(--accent-green); font-weight: 700; flex-shrink: 0; margin-top: 2px; }
.list-arrow li::before { content: '→'; color: var(--accent-yellow); font-weight: 700; flex-shrink: 0; margin-top: 2px; }
.list-bullet li::before { content: '•'; color: var(--accent-yellow); font-weight: 700; flex-shrink: 0; margin-top: 2px; }
.list-bullet li { display: flex; align-items: flex-start; gap: 10px; margin-bottom: 8px; color: var(--text-secondary); font-size: 0.95rem; }
.sticky-top { position: sticky; top: calc(var(--navbar-height) + 44px); }
.text-sm { font-size: 0.85rem; }
.text-xs { font-size: 0.75rem; }
.font-mono { font-family: var(--font-mono); }
.bold { font-weight: 700; }
.w-full { width: 100%; }
.rounded { border-radius: var(--radius-md); }
.hidden { display: none !important; }
.block { display: block; }
.inline-block { display: inline-block; }

/* Solved Example Styling */
.solved-example {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
  margin-bottom: 24px;
}
.solved-header {
  background: var(--bg-card-deep);
  padding: 14px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-subtle);
}
.solved-body { padding: 20px 24px; }
.solved-section-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin-bottom: 6px;
  margin-top: 14px;
}
.solved-section-label:first-child { margin-top: 0; }