/* Nath Algebra Lab - Premium Styling System */

:root {
  /* Colors */
  --bg-dark: hsl(222, 47%, 5%);
  --bg-dark-rgb: 9, 13, 22;
  --panel-bg: hsla(222, 40%, 10%, 0.5);
  --panel-border: hsla(222, 50%, 90%, 0.08);
  --panel-border-hover: hsla(222, 50%, 90%, 0.18);
  
  --text-main: hsl(210, 40%, 96%);
  --text-muted: hsl(215, 20%, 65%);
  --text-dark: hsl(222, 30%, 15%);
  
  --accent-purple: hsl(271, 91%, 65%);
  --accent-purple-glow: hsla(271, 91%, 65%, 0.25);
  --accent-blue: hsl(217, 91%, 60%);
  --accent-blue-glow: hsla(217, 91%, 60%, 0.25);
  --accent-cyan: hsl(190, 90%, 50%);
  --accent-emerald: hsl(142, 70%, 45%);
  --accent-emerald-glow: hsla(142, 70%, 45%, 0.2);
  --accent-rose: hsl(350, 89%, 60%);
  --accent-rose-glow: hsla(350, 89%, 60%, 0.2);
  
  --accent-light: hsl(210, 100%, 85%);
  --accent-glow: hsla(271, 91%, 65%, 0.15);

  /* Spacing & Borders */
  --radius-sm: 8px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.15);
  --shadow-glow: 0 0 20px 2px hsla(271, 91%, 65%, 0.15);
}

/* Global Reset & Base */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Outfit', sans-serif;
  background-color: var(--bg-dark);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
}

/* Decorative background glowing blobs */
.blob {
  position: fixed;
  border-radius: 50%;
  filter: blur(140px);
  z-index: -1;
  opacity: 0.35;
  pointer-events: none;
  transition: all var(--transition-slow);
}

.blob-purple {
  width: 450px;
  height: 450px;
  background: radial-gradient(circle, var(--accent-purple) 0%, transparent 70%);
  top: -100px;
  right: -50px;
}

.blob-blue {
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, var(--accent-blue) 0%, transparent 70%);
  bottom: -150px;
  left: -100px;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: rgba(var(--bg-dark-rgb), 0.5);
}

::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.12);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: rgba(255, 255, 255, 0.25);
}

/* Container */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Header & Nav */
header {
  background: rgba(9, 13, 22, 0.4);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--panel-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.logo-icon {
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-size: 1.8rem;
}

.logo-accent {
  background: linear-gradient(90deg, var(--accent-blue), var(--accent-cyan));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

nav {
  display: flex;
  gap: 0.5rem;
}

.nav-btn {
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-muted);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.6rem 1.2rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.nav-btn:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.03);
}

.nav-btn.active {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.06);
  border-color: var(--panel-border-hover);
  box-shadow: var(--shadow-sm);
}

/* Hero Section */
.hero-section {
  text-align: center;
  max-width: 800px;
  margin: 1.5rem auto 3rem;
}

.hero-section h1 {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -1px;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--text-main) 30%, var(--text-muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-section p {
  font-size: 1.15rem;
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  max-width: 600px;
  margin: 0 auto;
}

.stat-card {
  background: var(--panel-bg);
  backdrop-filter: blur(8px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-num {
  font-size: 2rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 0.25rem;
}

/* Tab Content Visibility */
.tab-content {
  display: none;
  animation: fadeIn 0.4s ease-in-out forwards;
}

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

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Category Tabs */
.category-tabs {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.cat-btn {
  background: var(--panel-bg);
  border: 1px solid var(--panel-border);
  color: var(--text-muted);
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  padding: 0.8rem 1.5rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  transition: all var(--transition-normal);
  backdrop-filter: blur(8px);
}

.cat-btn:hover {
  color: var(--text-main);
  border-color: var(--panel-border-hover);
  transform: translateY(-2px);
}

.cat-btn.active {
  color: var(--text-main);
  background: linear-gradient(135deg, var(--accent-purple-glow), rgba(255,255,255,0.02));
  border-color: var(--accent-purple);
  box-shadow: var(--shadow-glow);
}

/* Category Info Card */
.category-info-card {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-bottom: 2rem;
  text-align: center;
}

.category-info-card h3 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.category-info-card p {
  color: var(--text-muted);
  margin-bottom: 1.2rem;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

.formula-box {
  background: rgba(0, 0, 0, 0.25);
  border-radius: var(--radius-sm);
  padding: 1rem;
  display: inline-block;
  font-size: 1.25rem;
  border: 1px dashed var(--panel-border);
}

/* Worksheets Layout Split */
.worksheets-layout {
  display: grid;
  grid-template-columns: 1fr 1.2fr;
  gap: 2rem;
  align-items: start;
}

/* Exercise List Container */
.exercise-list-container {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.exercise-list-container h4 {
  font-size: 1rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
  font-weight: 500;
}

.exercise-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
  gap: 0.75rem;
  max-height: 520px;
  overflow-y: auto;
  padding-right: 0.5rem;
}

.ex-btn {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--panel-border);
  color: var(--text-main);
  padding: 0.8rem;
  border-radius: var(--radius-sm);
  font-family: 'Fira Code', monospace;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
}

.ex-btn:hover {
  background: rgba(255, 255, 255, 0.07);
  border-color: var(--panel-border-hover);
  transform: translateY(-2px);
}

.ex-btn.active {
  background: linear-gradient(135deg, var(--accent-blue-glow), transparent);
  border-color: var(--accent-blue);
  box-shadow: 0 0 10px 1px rgba(59, 130, 246, 0.15);
}

.ex-id {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
}

/* Detail Explanation Panel */
.detail-panel {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 2rem;
  min-height: 480px;
  position: sticky;
  top: 100px;
}

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  min-height: 400px;
  color: var(--text-muted);
}

.empty-icon {
  font-size: 3.5rem;
  margin-bottom: 1.5rem;
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.animate-bounce {
  animation: bounce 2s infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

.empty-state h3 {
  font-size: 1.25rem;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.detail-header {
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--panel-border);
  padding-bottom: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
}

.detail-header-left {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.copy-btn {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--panel-border);
  color: var(--text-muted);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
  backdrop-filter: blur(4px);
}

.copy-btn:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.08);
  border-color: var(--panel-border-hover);
  transform: translateY(-1px);
}

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

.copy-btn.copied {
  color: var(--text-main);
  background: var(--accent-emerald-glow);
  border-color: var(--accent-emerald);
  box-shadow: 0 0 10px 1px rgba(16, 185, 129, 0.2);
}

.category-badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  padding: 0.3rem 0.8rem;
  border-radius: 50px;
  background: var(--accent-purple-glow);
  color: var(--text-main);
  border: 1px solid var(--accent-purple);
  margin-bottom: 0.75rem;
}

.badge-emerald {
  background: var(--accent-emerald-glow);
  color: var(--text-main);
  border-color: var(--accent-emerald);
}

.detail-header h2 {
  font-size: 1.8rem;
  font-weight: 800;
}

.result-highlight {
  background: linear-gradient(90deg, rgba(var(--bg-dark-rgb), 0.7), transparent);
  border-left: 4px solid var(--accent-blue);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 1.2rem 1.5rem;
  margin-bottom: 2rem;
}

.result-label {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: 0.5px;
  margin-bottom: 0.4rem;
}

.result-math {
  font-size: 1.45rem;
  font-weight: 700;
  color: var(--accent-light);
}

/* Steps Timeline styling */
.steps-timeline h4 {
  font-size: 1.1rem;
  margin-bottom: 1.2rem;
  font-weight: 600;
}

/* Keyframes for step animations */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(15px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.step-card {
  position: relative;
  padding-left: 2rem;
  margin-bottom: 2rem;
  opacity: 0;
  transform: translateY(15px);
  animation: fadeInUp 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards;
  animation-delay: calc(var(--step-index, 0) * 0.12s);
  transition: transform var(--transition-normal) cubic-bezier(0.16, 1, 0.3, 1);
}

.step-card:hover {
  transform: translateX(4px);
}

.step-card::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: -28px;
  width: 2px;
  background: var(--panel-border);
}

.step-card:last-child::before {
  display: none;
}

.step-number {
  position: absolute;
  left: 0;
  top: 4px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent-purple);
  border: 3px solid var(--bg-dark);
  box-shadow: 0 0 8px var(--accent-purple);
  transition: transform var(--transition-normal) cubic-bezier(0.16, 1, 0.3, 1), box-shadow var(--transition-normal);
}

.step-card:hover .step-number {
  transform: scale(1.3);
  box-shadow: 0 0 12px var(--accent-purple);
}

.step-title {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
  color: var(--text-main);
}

.step-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
}

.step-desc code {
  font-family: 'Fira Code', monospace;
  background: rgba(0,0,0,0.25);
  padding: 0.1rem 0.3rem;
  border-radius: 4px;
  font-size: 0.85rem;
}

/* Inverted Check Card Styling */
.check-card {
  position: relative;
  background: var(--text-main);
  color: var(--text-dark);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-top: 2.5rem;
  margin-bottom: 1.5rem;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.4), 0 8px 16px -6px rgba(0, 0, 0, 0.4);
  border: 1px solid rgba(255, 255, 255, 0.8);
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: 1rem;
  row-gap: 0.5rem;
  align-items: center;
  opacity: 0;
  transform: translateY(15px);
  animation: fadeInUp 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards;
  animation-delay: calc(var(--step-index, 0) * 0.12s);
  transition: transform var(--transition-normal) cubic-bezier(0.16, 1, 0.3, 1), box-shadow var(--transition-normal);
}

.check-card:hover {
  transform: translateY(-4px) scale(1.01);
  box-shadow: 0 15px 30px -5px rgba(0, 0, 0, 0.5), 0 10px 20px -6px rgba(0, 0, 0, 0.5);
}

.check-icon {
  grid-column: 1;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  color: var(--text-main);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  box-shadow: 0 4px 10px rgba(168, 85, 247, 0.3);
  transition: transform var(--transition-normal) cubic-bezier(0.16, 1, 0.3, 1);
}

.check-card:hover .check-icon {
  transform: rotate(15deg) scale(1.1);
}

.check-title {
  grid-column: 2;
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text-dark);
  letter-spacing: -0.2px;
}

.check-desc {
  grid-column: 1 / span 2;
  font-size: 0.95rem;
  color: hsl(222, 20%, 25%);
  line-height: 1.6;
  margin-top: 0.5rem;
}

/* Override KaTeX for light background check card */
.check-card .katex {
  color: var(--text-dark) !important;
}

.check-card .katex-display {
  color: var(--text-dark) !important;
  background: rgba(0, 0, 0, 0.03);
  border-radius: var(--radius-sm);
  padding: 0.75rem 0.5rem;
  margin: 0.75rem 0;
  border: 1px solid rgba(0, 0, 0, 0.05);
}

.check-card strong {
  color: hsl(222, 35%, 10%);
}

.check-card code {
  font-family: 'Fira Code', monospace;
  background: rgba(0, 0, 0, 0.06);
  color: var(--text-dark);
  padding: 0.15rem 0.35rem;
  border-radius: 4px;
  font-size: 0.85rem;
}

/* Interactive Solver tab styles */
.solver-container {
  display: grid;
  grid-template-columns: 1fr 1.2fr;
  gap: 2rem;
  align-items: start;
}

.solver-input-card {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 2rem;
}

.solver-input-card h2 {
  font-size: 1.6rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.solver-input-card p {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.input-group {
  margin-bottom: 1.5rem;
}

.input-group label {
  display: block;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.input-wrapper input {
  width: 100%;
  background: rgba(0, 0, 0, 0.3);
  border: 1px solid var(--panel-border);
  color: var(--text-main);
  font-family: 'Fira Code', monospace;
  font-size: 1.1rem;
  padding: 1rem 3rem 1rem 1.2rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.input-wrapper input:focus {
  outline: none;
  border-color: var(--accent-purple);
  box-shadow: 0 0 12px 1px rgba(168, 85, 247, 0.18);
  background: rgba(0,0,0,0.4);
}

.clear-btn {
  position: absolute;
  right: 1rem;
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1.1rem;
  transition: color var(--transition-fast);
}

.clear-btn:hover {
  color: var(--text-main);
}

.format-guide {
  background: rgba(0,0,0,0.15);
  border-radius: var(--radius-sm);
  padding: 1.2rem;
  border: 1px solid rgba(255,255,255,0.02);
}

.format-guide h5 {
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
  color: var(--text-main);
}

.format-guide ul {
  list-style: none;
}

.format-guide li {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.format-guide li::before {
  content: "•";
  color: var(--accent-purple);
}

.format-guide code {
  font-family: 'Fira Code', monospace;
  background: rgba(0,0,0,0.2);
  padding: 0.1rem 0.3rem;
  border-radius: 4px;
  color: var(--accent-light);
}

.solver-result-panel {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 2rem;
  min-height: 460px;
}

.solver-error {
  display: flex;
  gap: 1rem;
  background: var(--accent-rose-glow);
  border: 1px solid var(--accent-rose);
  padding: 1.2rem;
  border-radius: var(--radius-sm);
  color: var(--text-main);
  animation: shake 0.3s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-5px); }
  75% { transform: translateX(5px); }
}

.error-icon {
  font-size: 1.8rem;
  color: var(--accent-rose);
}

.solver-error h4 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.solver-error p {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Practice Quiz Styles */
.practice-container {
  max-width: 700px;
  margin: 0 auto;
}

.practice-setup-card {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 2.5rem;
  text-align: center;
}

.practice-setup-card h2 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
}

.practice-setup-card p {
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.quiz-options h4 {
  font-size: 1rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 1.2rem;
}

.quiz-cats {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.quiz-cat-btn {
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--panel-border);
  color: var(--text-main);
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 600;
  padding: 1.2rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 1rem;
  transition: all var(--transition-normal);
}

.quiz-cat-btn:hover {
  background: rgba(255,255,255,0.07);
  border-color: var(--accent-blue);
  transform: translateX(5px);
}

.quiz-cat-btn i {
  font-size: 1.3rem;
  color: var(--accent-blue);
}

.quiz-cat-all {
  background: linear-gradient(90deg, rgba(168, 85, 247, 0.1), rgba(59, 130, 246, 0.1));
}

.quiz-cat-all:hover {
  border-color: var(--accent-purple);
}

.quiz-cat-all i {
  color: var(--accent-purple);
}

/* Active Quiz Card */
.quiz-card {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 2.5rem;
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--panel-border);
  padding-bottom: 1.2rem;
  margin-bottom: 1.5rem;
}

.quiz-header h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-top: 0.25rem;
}

.quiz-score-badge {
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgb(245, 158, 11);
  color: rgb(245, 158, 11);
  font-weight: 700;
  font-size: 0.9rem;
  padding: 0.4rem 0.8rem;
  border-radius: 50px;
}

.quiz-question-box {
  background: rgba(0,0,0,0.15);
  border-radius: var(--radius-sm);
  padding: 1.5rem;
  text-align: center;
  margin-bottom: 2rem;
}

.quiz-question-box p {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
}

.quiz-math-display {
  font-size: 1.8rem;
  font-weight: 700;
}

.quiz-options-container {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.8rem;
  margin-bottom: 2rem;
}

.quiz-option-btn {
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--panel-border);
  color: var(--text-main);
  font-family: inherit;
  font-size: 1.1rem;
  padding: 1.1rem 1.5rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-align: left;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.quiz-option-btn:hover {
  background: rgba(255,255,255,0.07);
  border-color: var(--panel-border-hover);
  transform: translateY(-2px);
}

.quiz-option-btn.correct {
  background: var(--accent-emerald-glow) !important;
  border-color: var(--accent-emerald) !important;
  color: var(--text-main) !important;
}

.quiz-option-btn.wrong {
  background: var(--accent-rose-glow) !important;
  border-color: var(--accent-rose) !important;
  color: var(--text-main) !important;
}

/* Feedback Box */
.quiz-feedback-box {
  background: rgba(255,255,255,0.02);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  animation: slideUp 0.3s ease;
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.feedback-status {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1.2rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.feedback-status.correct {
  color: var(--accent-emerald);
}

.feedback-status.wrong {
  color: var(--accent-rose);
}

.feedback-desc {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-bottom: 1.2rem;
}

.next-btn {
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-cyan));
  color: var(--text-main);
  border: none;
  font-family: inherit;
  font-weight: 700;
  padding: 0.8rem 1.5rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.next-btn:hover {
  box-shadow: 0 0 15px rgba(59, 130, 246, 0.4);
  transform: translateY(-2px);
}

.quiz-footer {
  border-top: 1px solid var(--panel-border);
  padding-top: 1rem;
}

.quit-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.9rem;
  transition: color var(--transition-fast);
}

.quit-btn:hover {
  color: var(--accent-rose);
}

/* Quiz finished view */
.quiz-finished-card {
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 3rem;
  text-align: center;
}

.trophy-icon {
  font-size: 4.5rem;
  margin-bottom: 1.5rem;
  background: linear-gradient(135deg, #f59e0b, #fbbf24);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.quiz-finished-card h2 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.quiz-finished-card p {
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.results-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  max-width: 500px;
  margin: 0 auto 2.5rem;
}

.result-stat {
  background: rgba(0,0,0,0.15);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  padding: 1.2rem;
}

.finished-actions {
  display: flex;
  justify-content: center;
  gap: 1rem;
}

.restart-btn {
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  border: none;
  color: var(--text-main);
  font-family: inherit;
  font-weight: 700;
  padding: 0.8rem 1.6rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.restart-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.back-btn {
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--panel-border);
  color: var(--text-main);
  font-family: inherit;
  font-weight: 600;
  padding: 0.8rem 1.6rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.back-btn:hover {
  background: rgba(255,255,255,0.08);
  border-color: var(--panel-border-hover);
}

/* Footer Styling */
footer {
  border-top: 1px solid var(--panel-border);
  background: rgba(5, 7, 12, 0.9);
  padding: 2rem 1.5rem;
  margin-top: 5rem;
  text-align: center;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.footer-container {
  max-width: 1280px;
  margin: 0 auto;
}

.footer-sub {
  font-size: 0.8rem;
  margin-top: 0.5rem;
  opacity: 0.7;
}

/* Helper hidden utilities */
.hidden {
  display: none !important;
}

.text-purple {
  color: var(--accent-purple) !important;
}

.text-blue {
  color: var(--accent-blue) !important;
}

.text-emerald {
  color: var(--accent-emerald) !important;
}

/* Active Operation Info in Header */
.header-center-info {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.08);
  padding: 0.35rem 1.25rem;
  border-radius: var(--radius-md);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: all var(--transition-normal);
  max-width: 450px;
  box-shadow: var(--shadow-sm);
}

.header-center-info.hidden {
  display: none !important;
}

.header-center-info:not(.hidden) {
  animation: fadeInDown 0.3s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

.active-badge {
  font-weight: 700;
  color: var(--accent-cyan);
  text-transform: uppercase;
  font-size: 0.62rem;
  letter-spacing: 1px;
  flex-shrink: 0;
  opacity: 0.8;
  line-height: 1;
}

.active-expr {
  font-family: 'Fira Code', monospace;
  font-weight: 600;
  color: var(--text-main);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  font-size: 1.15rem;
  display: inline-flex;
  align-items: center;
  line-height: 1.2;
}

.active-expr .katex {
  font-size: 0.95em;
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Responsiveness Settings */
@media (max-width: 1024px) {
  .worksheets-layout, .solver-container {
    grid-template-columns: 1fr;
  }
  
  .detail-panel {
    position: static;
    min-height: auto;
  }
}

@media (max-width: 768px) {
  .hero-section h1 {
    font-size: 2.2rem;
  }
  
  .stats-grid {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
  
  .results-stats {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
  
  .finished-actions {
    flex-direction: column;
    align-items: stretch;
  }
  
  .header-container {
    flex-direction: column;
    align-items: center;
  }
  
  .header-center-info {
    margin: 0.25rem 0;
    max-width: 90%;
    justify-content: center;
  }
}