/* =============================================
   Frontend Developer Assessment Platform
   Design System & Global Styles
   ============================================= */

/* Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Plus+Jakarta+Sans:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* CSS Variables / Design Tokens */
:root {
  /* Colors - Dark Theme */
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-tertiary: #1a1a2e;
  --bg-card: rgba(26, 26, 46, 0.6);
  --bg-card-hover: rgba(36, 36, 66, 0.8);

  /* Accent Colors */
  --accent-primary: #4f46e5;
  --accent-secondary: #7c3aed;
  --accent-gradient: linear-gradient(135deg, #4f46e5 0%, #7c3aed 50%, #a855f7 100%);
  --accent-glow: 0 0 40px rgba(79, 70, 229, 0.3);

  /* Status Colors */
  --success: #10b981;
  --success-bg: rgba(16, 185, 129, 0.1);
  --error: #ef4444;
  --error-bg: rgba(239, 68, 68, 0.1);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.1);
  --info: #3b82f6;
  --info-bg: rgba(59, 130, 246, 0.1);

  /* Text Colors */
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  /* Border Colors */
  --border-primary: rgba(148, 163, 184, 0.1);
  --border-secondary: rgba(148, 163, 184, 0.2);
  --border-accent: rgba(79, 70, 229, 0.5);

  /* Category Colors */
  --html-color: #e34c26;
  --css-color: #264de4;
  --js-color: #f7df1e;
  --git-color: #f05032;
  --challenge-color: #a855f7;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.3), 0 8px 10px -6px rgba(0, 0, 0, 0.3);

  /* Glassmorphism */
  --glass-bg: rgba(26, 26, 46, 0.6);
  --glass-border: rgba(255, 255, 255, 0.1);
  --glass-blur: blur(20px);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Plus Jakarta Sans', 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Background Pattern */
body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background:
    radial-gradient(ellipse at 20% 20%, rgba(79, 70, 229, 0.15) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 80%, rgba(124, 58, 237, 0.1) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 50%, rgba(168, 85, 247, 0.05) 0%, transparent 70%);
  pointer-events: none;
  z-index: -1;
}

/* Typography */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
}

h2 {
  font-size: clamp(1.5rem, 4vw, 2.5rem);
}

h3 {
  font-size: clamp(1.25rem, 3vw, 1.75rem);
}

h4 {
  font-size: 1.25rem;
}

p {
  color: var(--text-secondary);
  max-width: 65ch;
}

a {
  color: var(--accent-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--accent-secondary);
}

/* Container */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.container-narrow {
  max-width: 800px;
}

/* =============================================
   Header / Navigation
   ============================================= */

.header {
  position: sticky;
  top: 0;
  z-index: 100;
  padding: var(--space-lg) 0;
  background: rgba(10, 10, 15, 0.8);
  backdrop-filter: var(--glass-blur);
  border-bottom: 1px solid var(--border-primary);
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 1.5rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.logo-icon {
  display: flex;
  align-items: center;
  justify-content: center;
}

.logo-img {
  height: 48px;
  width: auto;
  filter: invert(1) brightness(2);
  object-fit: contain;
}

.footer .logo-img {
  height: 32px;
  opacity: 0.9;
}

.nav {
  display: flex;
  gap: var(--space-md);
}

.nav-link {
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-weight: 500;
  transition: all var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
  color: var(--text-primary);
  background: var(--bg-tertiary);
}

/* =============================================
   Hero Section
   ============================================= */

.hero {
  padding: var(--space-3xl) 0;
  text-align: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-secondary);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-lg);
}

.hero-badge-dot {
  width: 8px;
  height: 8px;
  background: var(--success);
  border-radius: 50%;
  animation: pulse 2s infinite;
}

@keyframes pulse {

  0%,
  100% {
    opacity: 1;
  }

  50% {
    opacity: 0.5;
  }
}

.hero h1 {
  margin-bottom: var(--space-md);
}

.hero-title-accent {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.125rem;
  margin: 0 auto var(--space-xl);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--space-2xl);
  margin-top: var(--space-xl);
}

.hero-stat {
  text-align: center;
}

.hero-stat-value {
  display: block;
  font-size: 2.5rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-stat-label {
  font-size: 0.875rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* =============================================
   Category Cards
   ============================================= */

.categories {
  padding: var(--space-2xl) 0;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-xl);
}

.section-title {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-lg);
}

.category-card {
  position: relative;
  padding: var(--space-xl);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  backdrop-filter: var(--glass-blur);
  transition: all var(--transition-base);
  overflow: hidden;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  min-height: 280px;
}

.category-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--card-accent, var(--accent-gradient));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.category-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-accent);
  box-shadow: var(--accent-glow);
}

.category-card:hover::before {
  opacity: 1;
}

.category-card.html {
  --card-accent: var(--html-color);
}

.category-card.css {
  --card-accent: var(--css-color);
}

.category-card.js {
  --card-accent: var(--js-color);
}

.category-card.git {
  --card-accent: var(--git-color);
}

.category-card.challenge {
  --card-accent: var(--challenge-color);
}

.category-icon {
  width: 56px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-tertiary);
  border-radius: var(--radius-lg);
  font-size: 1.5rem;
  margin-bottom: var(--space-md);
}

.category-card.html .category-icon {
  background: rgba(227, 76, 38, 0.15);
  color: var(--html-color);
}

.category-card.css .category-icon {
  background: rgba(38, 77, 228, 0.15);
  color: var(--css-color);
}

.category-card.js .category-icon {
  background: rgba(247, 223, 30, 0.15);
  color: var(--js-color);
}

.category-card.git .category-icon {
  background: rgba(240, 80, 50, 0.15);
  color: var(--git-color);
}

.category-card.challenge .category-icon {
  background: rgba(168, 85, 247, 0.15);
  color: var(--challenge-color);
}

.category-title {
  font-size: 1.25rem;
  margin-bottom: var(--space-sm);
}

.hero-description {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto var(--space-xl);
  line-height: 1.6;
}

.stats-container {
  display: flex;
  justify-content: center;
  gap: var(--space-2xl);
  margin-top: var(--space-xl);
  flex-wrap: wrap;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-xs);
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1;
}

.stat-label {
  font-size: 0.875rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 600;
}

.tabs-container {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-bottom: var(--space-xl);

  /* Panel Styling */
  background: rgba(18, 18, 26, 0.8);
  /* var(--bg-secondary) with opacity */
  padding: var(--space-sm);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-primary);
  max-width: fit-content;
  margin-left: auto;
  margin-right: auto;
  box-shadow: var(--shadow-sm);
}

.tab-btn {
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--radius-md);
  font-weight: 500;
  font-size: 0.9rem;
  transition: all var(--transition-fast);
  border: 1px solid var(--border-primary);
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
}

.tab-btn:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
  transform: translateY(-2px);
}

.tab-btn.active {
  background: var(--accent-gradient);
  color: white;
  box-shadow: var(--accent-glow);
  border-color: transparent;
}

.category-description {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: var(--space-md);
  flex-grow: 1;
}

.category-meta {
  display: flex;
  gap: var(--space-md);
  font-size: 0.8rem;
  margin-top: auto;
}

.category-meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  color: var(--text-muted);
}

/* =============================================
   Quiz List
   ============================================= */

.quiz-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.quiz-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  transition: all var(--transition-base);
  cursor: pointer;
  text-decoration: none;
  color: inherit;
}

.quiz-item:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-accent);
  transform: translateX(8px);
}

.quiz-item-content {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.quiz-item-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  font-size: 1.25rem;
}

.quiz-item-info h4 {
  font-size: 1rem;
  margin-bottom: var(--space-xs);
}

.quiz-item-info p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.quiz-item-arrow {
  font-size: 1.25rem;
  color: var(--text-muted);
  transition: transform var(--transition-fast);
}

.quiz-item:hover .quiz-item-arrow {
  transform: translateX(4px);
  color: var(--accent-primary);
}

/* =============================================
   Quiz Page Styles
   ============================================= */

.quiz-header {
  padding: var(--space-xl) 0;
  border-bottom: 1px solid var(--border-primary);
  margin-bottom: var(--space-xl);
}

.quiz-header-content {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-lg);
}

.quiz-header-info h1 {
  font-size: 2rem;
  margin-bottom: var(--space-sm);
}

.quiz-progress {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.quiz-progress-bar {
  width: 200px;
  height: 8px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  background: var(--accent-gradient);
  border-radius: var(--radius-full);
  transition: width var(--transition-base);
}

.quiz-progress-text {
  font-size: 0.875rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* Question Card */
.question-card {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  margin-bottom: var(--space-lg);
  backdrop-filter: var(--glass-blur);
}

.question-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.question-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  font-weight: 700;
  flex-shrink: 0;
}

.question-text {
  font-size: 1.125rem;
  font-weight: 500;
  line-height: 1.5;
}

.question-type-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-xs) var(--space-sm);
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-top: var(--space-sm);
}

/* MCQ Options */
.options-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.option-item {
  position: relative;
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-secondary);
  border: 2px solid var(--border-primary);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.option-item:hover {
  border-color: var(--border-secondary);
  background: var(--bg-tertiary);
}

.option-item.selected {
  border-color: var(--accent-primary);
  background: rgba(79, 70, 229, 0.1);
}

.option-item.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.option-item.incorrect {
  border-color: var(--error);
  background: var(--error-bg);
}

.option-radio {
  width: 24px;
  height: 24px;
  border: 2px solid var(--border-secondary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.option-item.selected .option-radio {
  border-color: var(--accent-primary);
}

.option-item.selected .option-radio::after {
  content: '';
  width: 12px;
  height: 12px;
  background: var(--accent-primary);
  border-radius: 50%;
}

.option-item.correct .option-radio {
  border-color: var(--success);
  background: var(--success);
}

.option-item.correct .option-radio::after {
  content: '✓';
  color: white;
  font-size: 14px;
  font-weight: bold;
}

.option-item.incorrect .option-radio {
  border-color: var(--error);
  background: var(--error);
}

.option-item.incorrect .option-radio::after {
  content: '✗';
  color: white;
  font-size: 14px;
  font-weight: bold;
}

.option-checkbox {
  width: 24px;
  height: 24px;
  border: 2px solid var(--border-secondary);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.option-item.selected .option-checkbox {
  border-color: var(--accent-primary);
  background: var(--accent-primary);
}

.option-item.selected .option-checkbox::after {
  content: '✓';
  color: white;
  font-size: 14px;
  font-weight: bold;
}

.option-text {
  font-size: 1rem;
  color: var(--text-primary);
}

.option-letter {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-muted);
  flex-shrink: 0;
}

/* Text Input */
.text-input {
  width: 100%;
  padding: var(--space-md);
  background: var(--bg-secondary);
  border: 2px solid var(--border-primary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 1rem;
  transition: all var(--transition-fast);
}

.text-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.2);
}

.text-input::placeholder {
  color: var(--text-muted);
}

/* Code Input */
.code-input {
  width: 100%;
  min-height: 150px;
  padding: var(--space-md);
  background: var(--bg-primary);
  border: 2px solid var(--border-primary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.6;
  resize: vertical;
  transition: all var(--transition-fast);
}

.code-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.2);
}

/* =============================================
   Buttons
   ============================================= */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-xl);
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--accent-gradient);
  color: white;
  box-shadow: 0 4px 15px rgba(79, 70, 229, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(79, 70, 229, 0.4);
  color: white;
}

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

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-secondary);
}

.btn-secondary:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-accent);
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}

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

.btn-lg {
  padding: var(--space-lg) var(--space-2xl);
  font-size: 1.125rem;
}

.btn-sm {
  padding: var(--space-sm) var(--space-md);
  font-size: 0.875rem;
}

.btn-icon {
  width: 44px;
  height: 44px;
  padding: 0;
  border-radius: var(--radius-md);
}

/* Quiz Navigation */
.quiz-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--border-primary);
  margin-top: var(--space-xl);
}

/* =============================================
   Results Page
   ============================================= */

.results-container {
  max-width: 600px;
  margin: 0 auto;
  padding: var(--space-3xl) var(--space-lg);
  text-align: center;
}

.results-card {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  padding: var(--space-2xl);
  backdrop-filter: var(--glass-blur);
}

.results-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  font-size: 2.5rem;
}

.results-icon.success {
  background: var(--success-bg);
  color: var(--success);
}

.results-icon.warning {
  background: var(--warning-bg);
  color: var(--warning);
}

.results-icon.error {
  background: var(--error-bg);
  color: var(--error);
}

.results-score {
  font-size: 4rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--space-sm);
}

.results-label {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-xl);
}

.results-breakdown {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md);
  padding: var(--space-lg);
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-xl);
}

.results-stat {
  text-align: center;
}

.results-stat-value {
  font-size: 1.5rem;
  font-weight: 700;
}

.results-stat-value.correct {
  color: var(--success);
}

.results-stat-value.incorrect {
  color: var(--error);
}

.results-stat-value.skipped {
  color: var(--text-muted);
}

.results-stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.results-actions {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
}

/* =============================================
   Challenges Page
   ============================================= */

.challenges-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--space-lg);
}

.challenge-card {
  display: flex;
  flex-direction: column;
  min-height: 320px;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  backdrop-filter: var(--glass-blur);
  transition: all var(--transition-base);
  cursor: pointer;
}

.challenge-card:hover {
  border-color: var(--border-accent);
  transform: translateY(-4px);
}

.challenge-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.challenge-number {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 42px;
  width: 42px;
  height: 42px;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  font-weight: 700;
  font-size: 0.8rem;
  flex-shrink: 0;
}

.challenge-title {
  font-size: 1.1rem;
  font-weight: 600;
  flex: 1;
  line-height: 1.3;
}

.challenge-difficulty {
  flex-shrink: 0;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  white-space: nowrap;
}

.challenge-difficulty.easy {
  background: var(--success-bg);
  color: var(--success);
}

.challenge-difficulty.medium {
  background: var(--warning-bg);
  color: var(--warning);
}

.challenge-difficulty.hard {
  background: var(--error-bg);
  color: var(--error);
}

.challenge-description {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
  flex: 1;
}

.challenge-example {
  margin-top: var(--space-md);
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.challenge-example strong {
  color: var(--accent-primary);
}

.challenge-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-top: auto;
  padding-top: var(--space-md);
}

.challenge-tag {
  padding: var(--space-xs) var(--space-sm);
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
}

.challenge-video-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  background: linear-gradient(135deg, #a855f7 0%, #7c3aed 100%);
  color: white !important;
  font-weight: 600;
  text-decoration: none;
  transition: all var(--transition-fast);
  cursor: pointer;
  border: none;
  box-shadow: 0 2px 8px rgba(168, 85, 247, 0.3);
}

.challenge-video-link:hover {
  background: linear-gradient(135deg, #c084fc 0%, #a855f7 100%);
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 4px 12px rgba(168, 85, 247, 0.4);
}

/* =============================================
   Footer
   ============================================= */

.footer {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--border-primary);
  margin-top: var(--space-3xl);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-text {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-links {
  display: flex;
  gap: var(--space-lg);
}

.footer-link {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-link:hover {
  color: var(--text-primary);
}

/* =============================================
   Utilities
   ============================================= */

.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

.mb-sm {
  margin-bottom: var(--space-sm);
}

.mb-md {
  margin-bottom: var(--space-md);
}

.mb-lg {
  margin-bottom: var(--space-lg);
}

.mb-xl {
  margin-bottom: var(--space-xl);
}

.hidden {
  display: none !important;
}

.visible {
  display: block !important;
}

.fade-in {
  animation: fadeIn 0.3s ease forwards;
}

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

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.slide-up {
  animation: slideUp 0.4s ease forwards;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* =============================================
   Responsive Design
   ============================================= */

@media (max-width: 768px) {
  .header-content {
    flex-direction: column;
    gap: var(--space-md);
  }

  .logo {
    margin-bottom: var(--space-sm);
  }

  .nav {
    width: 100%;
    justify-content: center;
  }

  /* Stats vertical on mobile */
  .stats-container {
    flex-direction: column;
    gap: var(--space-md);
    width: 100%;
  }

  .category-grid {
    grid-template-columns: 1fr;
  }

  .quiz-header-content {
    flex-direction: column;
  }

  /* Full width buttons on mobile */
  .btn,
  .btn-primary,
  .btn-secondary,
  .challenge-video-link {
    width: 100%;
    justify-content: center;
  }

  /* Exception for small buttons (like Clear All) */
  .btn-sm {
    width: auto !important;
  }

  /* Prevent title wrapping in headers */
  .section-title h2 {
    white-space: nowrap;
  }

  /* Tabs wrapping but keeping pill shape or full width? 
     User said "buttons... like here". I'll default to full width for ease of tap. 
     Actually tab-btn might be better as row with wrapping for saving space. 
     I will leave tab-btn as is (wrapping row) unless it looks bad. */

  .quiz-progress {
    width: 100%;
  }

  .quiz-progress-bar {
    flex: 1;
  }

  .results-breakdown {
    grid-template-columns: 1fr;
  }

  .results-actions {
    flex-direction: column;
  }

  .challenges-grid {
    grid-template-columns: 1fr;
  }

  .footer-content {
    flex-direction: column;
    gap: var(--space-md);
    text-align: center;
  }
}

@media (max-width: 480px) {
  :root {
    --space-lg: 1rem;
    --space-xl: 1.5rem;
    --space-2xl: 2rem;
  }

  /* Code syntax responsiveness */
  code,
  pre {
    white-space: pre-wrap;
    word-break: break-word;
    font-size: 0.85rem;
  }

  .option-item {
    padding: var(--space-sm) var(--space-md);
    font-size: 0.9rem;
  }

  /* Ensure quiz options wrap text */
  .option-item span {
    word-break: break-word;
  }
}

/* =============================================
   Ad Container & Upsell Card Styles
   ============================================= */

.ad-container {
  margin-top: var(--space-xl);
  padding: var(--space-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  text-align: center;
  min-height: 90px;
}

.ad-container ins {
  display: block !important;
}

/* Smart Upsell Card */
.upsell-card {
  margin-top: var(--space-xl);
  padding: var(--space-lg);
  border: 2px solid;
  border-radius: var(--radius-xl);
  backdrop-filter: var(--glass-blur);
  animation: slideUp 0.4s ease-out;
}

.upsell-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
  font-weight: 600;
  font-size: 1.1rem;
}

.upsell-icon {
  font-size: 1.5rem;
}

.upsell-message {
  color: var(--text-primary);
}

.upsell-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
  flex-wrap: wrap;
}

.upsell-info {
  flex: 1;
  min-width: 200px;
}

.upsell-title {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: var(--space-xs);
  color: var(--text-primary);
}

.upsell-description {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: var(--space-sm);
}

.upsell-meta {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  font-size: 0.875rem;
}

.upsell-platform {
  background: var(--bg-tertiary);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  font-weight: 500;
}

.upsell-price {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.upsell-original-price {
  color: var(--text-muted);
  text-decoration: line-through;
  font-size: 0.85rem;
}

.upsell-sale-price {
  color: var(--success);
  font-weight: 700;
  font-size: 1.1rem;
}

.upsell-cta {
  flex-shrink: 0;
  white-space: nowrap;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Buy Me a Coffee Button */
.bmc-button {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  background: linear-gradient(135deg, #FF813F 0%, #FF5F5F 100%);
  color: white;
  font-weight: 600;
  font-size: 0.9rem;
  border-radius: var(--radius-full);
  transition: all var(--transition-base);
  text-decoration: none;
  box-shadow: 0 4px 14px rgba(255, 129, 63, 0.3);
}

.bmc-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(255, 129, 63, 0.4);
  color: white;
}

.bmc-button img {
  height: 20px;
  width: auto;
}

/* Support Section */
.support-section {
  text-align: center;
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--border-primary);
  margin-top: var(--space-2xl);
}

.support-section h3 {
  margin-bottom: var(--space-sm);
  font-size: 1.25rem;
}

.support-section p {
  color: var(--text-muted);
  margin-bottom: var(--space-lg);
  max-width: 400px;
  margin-left: auto;
  margin-right: auto;
}

/* Upsell responsive */
@media (max-width: 600px) {
  .upsell-content {
    flex-direction: column;
    align-items: flex-start;
  }

  .upsell-cta {
    width: 100%;
    text-align: center;
  }

  .upsell-meta {
    flex-wrap: wrap;
  }
}