/* ==========================================================================
   LeetCode Solutions - Premium Design System
   ========================================================================== */

/* --- 1. Variables & Theming --- */
:root {
  /* Colors - Dark Theme (Default) */
  --bg-color: #060611;
  --surface-color: #0c0c24;
  --surface-hover: #151538;
  --surface-translucent: rgba(12, 12, 36, 0.7);
  
  --border-color: rgba(99, 102, 241, 0.12);
  --border-hover: rgba(139, 92, 246, 0.5);
  --border-gradient: linear-gradient(135deg, rgba(99, 102, 241, 0.5), rgba(167, 139, 250, 0.5));
  
  --accent-primary: #818cf8;
  --accent-secondary: #a78bfa;
  --accent-tertiary: #22d3ee;
  
  --easy-color: #4ade80;
  --medium-color: #fbbf24;
  --hard-color: #f87171;
  --easy-bg: rgba(74, 222, 128, 0.1);
  --medium-bg: rgba(251, 191, 36, 0.1);
  --hard-bg: rgba(248, 113, 113, 0.1);
  
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  --code-bg: #0d1117;
  
  /* Languages */
  --lang-cpp: #3b82f6;
  --lang-python: #eab308;
  --lang-sql: #f97316;
  --lang-javascript: #facc15;
  --lang-typescript: #3178c6;
  --lang-csharp: #10b981;
  --lang-java: #ef4444;
  
  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  
  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-24: 6rem;
  
  /* Radii */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.3);
  
  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 300ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 500ms cubic-bezier(0.4, 0, 0.2, 1);
}

body.light-theme {
  --bg-color: #f8fafc;
  --surface-color: #ffffff;
  --surface-hover: #f1f5f9;
  --surface-translucent: rgba(255, 255, 255, 0.8);
  
  --border-color: rgba(148, 163, 184, 0.2);
  --border-hover: rgba(99, 102, 241, 0.4);
  
  --accent-primary: #4f46e5;
  --accent-secondary: #7c3aed;
  --accent-tertiary: #0891b2;
  
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  
  --code-bg: #f1f5f9;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --shadow-glow: 0 0 20px rgba(79, 70, 229, 0.2);
}

/* --- 2. Base & Reset --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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


body {
  background-color: var(--bg-color);
  background-image: 
    linear-gradient(var(--border-color) 1px, transparent 1px),
    linear-gradient(90deg, var(--border-color) 1px, transparent 1px);
  background-size: 50px 50px;
  background-position: center top;
  color: var(--text-primary);

  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

a {
  color: inherit;
  text-decoration: none;
}

ul, ol {
  list-style: none;
}

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

/* Scrollbar */
::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: var(--bg-color);
}

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--border-hover);
}

/* --- 3. Animations --- */
@keyframes gradientShift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

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

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.8; transform: scale(1.05); }
}

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

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* --- 4. Globals --- */
.gradient-text {
  background: linear-gradient(to right, var(--accent-primary), var(--accent-secondary), var(--accent-tertiary));
  background-size: 200% auto;
  color: transparent;
  -webkit-background-clip: text;
  background-clip: text;
  animation: gradientShift 5s ease infinite;
  display: inline-block;
}

.visible {
  animation: fadeInUp 0.6s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

/* --- 5. Header --- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--surface-translucent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
}

.site-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary), var(--accent-tertiary));
  z-index: 101;
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-4) var(--space-6);
  position: relative;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  font-size: 1.25rem;
  letter-spacing: -0.025em;
  transition: transform var(--transition-fast);
}

.logo:hover {
  transform: scale(1.02);
}

.logo-icon {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.logo-accent {
  color: var(--accent-primary);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.nav-link {
  color: var(--text-secondary);
  font-weight: 500;
  position: relative;
  transition: color var(--transition-fast);
}

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

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent-primary);
  transition: width var(--transition-normal);
  border-radius: var(--radius-full);
}

.nav-link:hover::after {
  width: 100%;
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  color: var(--text-primary);
  border-color: var(--accent-primary);
  transform: rotate(15deg) scale(1.1);
}

.icon-sun {
  display: none;
}

body.light-theme .icon-sun {
  display: block;
}

body.light-theme .icon-moon {
  display: none;
}

.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: var(--space-2);
}

.mobile-menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  transition: var(--transition-fast);
}

/* --- 6. Hero Section --- */
.hero-section {
  position: relative;
  padding: var(--space-24) var(--space-6) var(--space-16);
  text-align: center;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.hero-section::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 80vw;
  height: 80vw;
  max-width: 1000px;
  max-height: 1000px;
  transform: translate(-50%, -50%);
  background: radial-gradient(circle, rgba(99, 102, 241, 0.15) 0%, rgba(6, 6, 17, 0) 70%);
  z-index: -1;
  pointer-events: none;
}

.hero-section::after {
  content: '';
  position: absolute;
  top: 10%;
  right: 10%;
  width: 300px;
  height: 300px;
  background: radial-gradient(circle, rgba(34, 211, 238, 0.1) 0%, transparent 70%);
  border-radius: 50%;
  filter: blur(40px);
  z-index: -1;
  animation: float 10s ease-in-out infinite;
}

.hero-content {
  max-width: 800px;
  position: relative;
  z-index: 1;
}

.hero-title {
  font-size: clamp(3rem, 5vw, 5rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.04em;
  margin-bottom: var(--space-6);
  color: var(--text-primary);
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto var(--space-8);
  line-height: 1.6;
}

/* --- 7. Stats Section --- */
.stats-section {
  padding: var(--space-8) var(--space-6);
  max-width: 1400px;
  margin: 0 auto;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-6);
}

.stat-card {
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  transition: all var(--transition-normal);
  backdrop-filter: blur(8px);
  opacity: 0; /* for scroll reveal */
  transform: translateY(20px);
}

.stat-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: var(--border-hover);
}

.stat-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: transparent;
  transition: background var(--transition-normal);
}

.stat-card.stat-total::before { background: var(--accent-primary); }
.stat-card.stat-easy::before { background: var(--easy-color); }
.stat-card.stat-medium::before { background: var(--medium-color); }
.stat-card.stat-hard::before { background: var(--hard-color); }

.stat-number {
  font-size: 3rem;
  font-weight: 800;
  font-family: var(--font-mono);
  line-height: 1;
  margin-bottom: var(--space-2);
}

.stat-total .stat-number { color: var(--accent-primary); }
.stat-easy .stat-number { color: var(--easy-color); }
.stat-medium .stat-number { color: var(--medium-color); }
.stat-hard .stat-number { color: var(--hard-color); }

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

/* --- 8. Content Section & Controls --- */
.content-section {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-8) var(--space-6) var(--space-24);
}

.controls-bar {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  margin-bottom: var(--space-10);
  background: var(--surface-translucent);
  padding: var(--space-6);
  border-radius: var(--radius-xl);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-md);
}

.search-wrapper {
  position: relative;
  width: 100%;
}

.search-icon {
  position: absolute;
  left: var(--space-4);
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  width: 20px;
  height: 20px;
  pointer-events: none;
}

#search-input {
  width: 100%;
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-4) var(--space-4) var(--space-4) var(--space-12);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: inherit;
  transition: all var(--transition-fast);
}

#search-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

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

.filter-section {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3);
}

.filter-group {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-8);
}

.filter-label {
  font-size: 0.875rem;
  color: var(--text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-right: var(--space-2);
}

.filter-btn {
  padding: var(--space-2) var(--space-4);
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  background: var(--surface-hover);
  color: var(--text-primary);
  border-color: var(--border-hover);
}

.filter-btn.active {
  background: var(--accent-primary);
  color: #fff;
  border-color: var(--accent-primary);
  box-shadow: var(--shadow-sm);
  transform: scale(1.05);
}

/* Specific Language Colors for Active Buttons */
.filter-btn[data-language="cpp"].active { background: var(--lang-cpp); border-color: var(--lang-cpp); }
.filter-btn[data-language="python"].active { background: var(--lang-python); border-color: var(--lang-python); color: #000; }
.filter-btn[data-language="sql"].active { background: var(--lang-sql); border-color: var(--lang-sql); }
.filter-btn[data-language="javascript"].active { background: var(--lang-javascript); border-color: var(--lang-javascript); color: #000; }
.filter-btn[data-language="java"].active { background: var(--lang-java); border-color: var(--lang-java); }
.filter-btn[data-language="typescript"].active { background: var(--lang-typescript); border-color: var(--lang-typescript); }
.filter-btn[data-language="csharp"].active { background: var(--lang-csharp); border-color: var(--lang-csharp); }

.results-count {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-left: auto;
}

/* --- 9. Problem Cards Grid --- */
.problems-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: var(--space-6);
}

.problem-card {
  display: flex;
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  flex-direction: column;
  background: var(--surface-translucent);
  border-radius: var(--radius-xl);
  border: 1px solid var(--border-color);
  overflow: hidden;
  text-decoration: none;
  color: inherit;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), border-color var(--transition-normal);
  position: relative;
  z-index: 1;
}

.problem-card::before {
  content: '';
  position: absolute;
  top: -2px;
  left: -2px;
  right: -2px;
  bottom: -2px;
  background: conic-gradient(from 180deg at 50% 50%, var(--accent-tertiary), var(--accent-primary), var(--accent-secondary), var(--accent-tertiary));
  z-index: -1;
  border-radius: calc(var(--radius-xl) + 2px);
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.problem-card::after {
  content: '';
  position: absolute;
  inset: 1px;
  background: var(--surface-translucent);
  border-radius: calc(var(--radius-xl) - 1px);
  z-index: -1;
  transition: background var(--transition-normal);
}

.problem-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-xl);
  border-color: transparent;
}

.problem-card:hover::before {
  opacity: 1;
  animation: spin 4s linear infinite;
}

.problem-card:hover::after {
  background: var(--surface-hover);
}

.card-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--border-color);
  background: rgba(0, 0, 0, 0.1);
}

.problem-number {
  font-family: var(--font-mono);
  color: var(--text-muted);
  font-size: 0.875rem;
  font-weight: 600;
}

.difficulty-badge, .lang-badge {
  padding: 2px 8px;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.difficulty-easy { background: var(--easy-bg); color: var(--easy-color); border: 1px solid rgba(74, 222, 128, 0.2); }
.difficulty-medium { background: var(--medium-bg); color: var(--medium-color); border: 1px solid rgba(251, 191, 36, 0.2); }
.difficulty-hard { background: var(--hard-bg); color: var(--hard-color); border: 1px solid rgba(248, 113, 113, 0.2); }

.lang-badge {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  margin-left: auto;
}

.lang-cpp { color: var(--lang-cpp); border-color: rgba(59, 130, 246, 0.3); }
.lang-python { color: var(--lang-python); border-color: rgba(234, 179, 8, 0.3); }
.lang-sql { color: var(--lang-sql); border-color: rgba(249, 115, 22, 0.3); }
.lang-javascript { color: var(--lang-javascript); border-color: rgba(250, 204, 21, 0.3); }
.lang-java { color: var(--lang-java); border-color: rgba(239, 68, 68, 0.3); }
.lang-typescript { color: var(--lang-typescript); border-color: rgba(49, 120, 198, 0.3); }
.lang-csharp { color: var(--lang-csharp); border-color: rgba(16, 185, 129, 0.3); }

.card-body {
  padding: var(--space-5);
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.problem-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  text-overflow: ellipsis;
}

.problem-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: auto;
}

.approach-tag {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
  transition: all var(--transition-fast);
}

.problem-card:hover .approach-tag {
  border-color: var(--border-hover);
  color: var(--text-secondary);
}

/* --- 10. Ads --- */
.ad-banner {
  width: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  margin: var(--space-8) 0;
}

.ad-container {
  background: var(--surface-translucent);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  text-align: center;
  position: relative;
  min-height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  font-size: 0.875rem;
}

.ad-label {
  position: absolute;
  top: -10px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--bg-color);
  padding: 0 var(--space-2);
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.ad-card {
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0.02);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-xl);
  min-height: 200px;
  color: var(--text-muted);
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* --- 11. Problem Page Layout --- */
.breadcrumb {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-6) var(--space-6) 0;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.breadcrumb a:hover {
  color: var(--accent-primary);
}

.breadcrumb-sep {
  color: var(--border-color);
}

.breadcrumb-current {
  color: var(--text-primary);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 300px;
}

.problem-layout {
  display: flex;
  gap: var(--space-8);
  max-width: 1400px;
  width: 100%;
  margin: 0 auto;
  padding: var(--space-6) var(--space-6) var(--space-24);
  align-items: flex-start;
  box-sizing: border-box;
}

.problem-main {
  flex: 1;
  min-width: 0;
  max-width: 100%;
  background: var(--surface-translucent);
  border-radius: var(--radius-2xl);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  box-sizing: border-box;
}

.problem-sidebar {
  width: 320px;
  flex-shrink: 0;
}

.sidebar-sticky {
  position: sticky;
  top: calc(80px + var(--space-6));
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.sidebar-info {
  background: var(--surface-translucent);
  border-radius: var(--radius-xl);
  border: 1px solid var(--border-color);
  padding: var(--space-5);
}

.sidebar-info h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--space-4);
  color: var(--text-primary);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--border-color);
}

.info-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-3) 0;
  border-bottom: 1px solid rgba(255,255,255,0.05);
  font-size: 0.875rem;
}

.info-item:last-child {
  border-bottom: none;
}

.info-label {
  color: var(--text-muted);
}

/* --- 12. Problem Page Content --- */
.problem-header-section {
  padding: var(--space-8);
  border-bottom: 1px solid var(--border-color);
  background: linear-gradient(to bottom, rgba(99, 102, 241, 0.05), transparent);
}

.problem-title {
  font-size: 2rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.problem-number-large {
  color: var(--accent-primary);
  font-family: var(--font-mono);
  font-size: 1.5rem;
}

.problem-meta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.description-section, .solution-section, .approach-section {
  padding: var(--space-8);
  border-bottom: 1px solid var(--border-color);
  box-sizing: border-box;
  max-width: 100%;
}

.approach-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: var(--space-6);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* LeetCode HTML Content Styling */
.description-content {
  font-size: 1.0625rem;
  line-height: 1.7;
  color: var(--text-secondary);
  word-wrap: break-word;
  overflow-wrap: break-word;
}

.description-content p { margin-bottom: var(--space-4); }
.description-content strong, .description-content b { color: var(--text-primary); font-weight: 600; }
.description-content em, .description-content i { color: var(--text-muted); }
.description-content ul, .description-content ol { margin: var(--space-4) 0; padding-left: var(--space-6); }
.description-content li { margin-bottom: var(--space-2); }
.description-content li::marker { color: var(--accent-primary); }

.description-content code {
  background: var(--code-bg);
  padding: 0.2em 0.4em;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.875em;
  color: var(--accent-tertiary);
  border: 1px solid var(--border-color);
  word-break: break-word;
}

.description-content pre {
  background: var(--code-bg);
  padding: var(--space-4);
  border-radius: var(--radius-lg);
  overflow-x: auto;
  margin: var(--space-6) 0;
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--accent-primary);
  max-width: 100%;
}

.description-content pre code {
  background: none;
  padding: 0;
  border: none;
  color: var(--text-primary);
  font-size: 0.875rem;
  word-break: normal;
  white-space: pre;
}

.description-content blockquote {
  border-left: 4px solid var(--border-hover);
  padding-left: var(--space-4);
  margin: var(--space-6) 0;
  color: var(--text-muted);
  font-style: italic;
  background: rgba(255,255,255,0.02);
  padding: var(--space-4);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.description-content img {
  max-width: 100%;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  margin: var(--space-6) 0;
  background: #fff; /* In case it's a transparent PNG meant for light bg */
}

/* Specific example block styles from LeetCode */
.description-content .example-block {
  background: var(--surface-hover);
  border-left: 4px solid var(--border-hover);
  padding: var(--space-4);
  border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
  margin: var(--space-4) 0;
}

/* Solution Block */
.solution-block {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.code-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  background: rgba(0,0,0,0.2);
  border-bottom: 1px solid var(--border-color);
}

.lang-label {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.copy-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-size: 0.75rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.copy-btn:hover {
  background: var(--surface-hover);
  color: var(--text-primary);
  border-color: var(--accent-primary);
}

.copy-btn svg {
  width: 14px;
  height: 14px;
}

.code-block {
  overflow-x: auto;
  background: var(--code-bg);
  width: 100%;
  max-width: 100%;
}

.code-block pre {
  margin: 0;
  padding: var(--space-5) !important;
  font-family: var(--font-mono) !important;
  font-size: 0.875rem !important;
  line-height: 1.6 !important;
  background: transparent !important;
  border-left: 2px solid var(--accent-secondary);
}

.code-block pre code {
  background: transparent;
  text-shadow: none !important;
  color: #c9d1d9; /* Base code color */
}

.no-solution {
  padding: var(--space-12) var(--space-6);
  text-align: center;
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-xl);
  color: var(--text-muted);
  font-style: italic;
  background: rgba(255,255,255,0.02);
}

/* Navigation */
.problem-nav {
  display: flex;
  justify-content: space-between;
  padding: var(--space-8);
  gap: var(--space-6);
}

.nav-prev, .nav-next {
  flex: 1;
  display: flex;
  flex-direction: row;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5);
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  text-decoration: none;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.nav-prev:hover, .nav-next:hover {
  background: var(--surface-hover);
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.nav-direction {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  font-weight: 600;
  margin-bottom: var(--space-2);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

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

.nav-prev:hover .nav-arrow { transform: translateX(-4px); color: var(--accent-primary); }
.nav-next:hover .nav-arrow { transform: translateX(4px); color: var(--accent-primary); }

.nav-next .nav-info { align-items: flex-end; text-align: right; }

.nav-title {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 1rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

/* --- 13. Footer --- */
.site-footer {
  border-top: 1px solid var(--border-color);
  background: var(--surface-translucent);
  padding: var(--space-12) var(--space-6);
  margin-top: auto;
}

.footer-content {
  max-width: 1400px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-6);
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: 1.25rem;
  font-weight: 700;
}

.footer-brand .logo-icon {
  width: 24px;
  height: 24px;
  font-size: 0.875rem;
}

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

/* --- 14. Prism JS Overrides --- */
code[class*="language-"], pre[class*="language-"] {
  color: #e2e8f0 !important;
  text-shadow: none !important;
  font-family: var(--font-mono) !important;
}

:not(pre) > code[class*="language-"], pre[class*="language-"] {
  background: var(--code-bg) !important;
}

.token.comment, .token.prolog, .token.doctype, .token.cdata { color: #64748b !important; font-style: italic; }
.token.punctuation { color: #94a3b8 !important; }
.token.namespace { opacity: .7 !important; }
.token.property, .token.tag, .token.constant, .token.symbol, .token.deleted { color: #f472b6 !important; }
.token.boolean, .token.number { color: #fdba74 !important; }
.token.selector, .token.attr-name, .token.string, .token.char, .token.builtin, .token.inserted { color: #86efac !important; }
.token.operator, .token.entity, .token.url, .language-css .token.string, .style .token.string { color: #93c5fd !important; }
.token.atrule, .token.attr-value, .token.keyword { color: #c084fc !important; }
.token.function, .token.class-name { color: #fcd34d !important; }
.token.regex, .token.important, .token.variable { color: #fca5a5 !important; }

.line-numbers .line-numbers-rows {
  border-right: 1px solid var(--border-color) !important;
}
.line-numbers-rows > span:before {
  color: var(--text-muted) !important;
}

/* --- 15. Responsive Design --- */
@media (max-width: 1200px) {
  .hero-title { font-size: 3.5rem; }
}

@media (max-width: 1024px) {
  .problem-layout {
    flex-direction: column;
    padding: var(--space-4) var(--space-2) var(--space-12);
  }
  .problem-sidebar {
    width: 100%;
  }
  .sidebar-sticky {
    position: static;
  }
  .sidebar-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--space-4);
  }
  .sidebar-info h3 {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  .nav-links {
    display: none; /* Hide on mobile */
    transform: none;
  }
  .mobile-menu-toggle {
    display: flex;
  }
  .hero-title {
    font-size: 2.5rem;
  }
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .controls-bar {
    padding: var(--space-4);
  }
  .filter-group {
    flex-direction: column;
    align-items: flex-start;
  }
  .problem-nav {
    flex-direction: column;
  }
  .nav-next, .nav-prev {
    flex-direction: column;
    justify-content: center;
    text-align: center;
    gap: 0.5rem;
  }
  .nav-next .nav-info, .nav-prev .nav-info {
    align-items: center;
    text-align: center;
  }
  .description-section, .solution-section, .approach-section {
    padding: var(--space-4) var(--space-2);
  }
}

@media (max-width: 480px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }
  .hero-title {
    font-size: 2rem;
  }
  .problem-title {
    font-size: 1.5rem;
  }
  .problems-grid {
    grid-template-columns: 1fr;
  }
}

/* ==========================================================================
   V2 Additions - Premium Enhancements
   ========================================================================== */

/* Header Glow Line */
.header-glow {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary), var(--accent-tertiary), var(--accent-secondary), var(--accent-primary));
  background-size: 200% 100%;
  animation: gradientShift 4s ease infinite;
}

/* Hero Orbs - Decorative Background */
.hero-bg {
  position: absolute;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
}

.hero-orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.15;
  animation: float 8s ease-in-out infinite;
}

.hero-orb-1 {
  width: 400px;
  height: 400px;
  background: var(--accent-primary);
  top: -100px;
  right: -100px;
  animation-delay: 0s;
}

.hero-orb-2 {
  width: 300px;
  height: 300px;
  background: var(--accent-secondary);
  bottom: -80px;
  left: -80px;
  animation-delay: -3s;
}

.hero-orb-3 {
  width: 200px;
  height: 200px;
  background: var(--accent-tertiary);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  animation-delay: -5s;
}

@keyframes float {
  0%, 100% { transform: translateY(0) scale(1); }
  50% { transform: translateY(-20px) scale(1.05); }
}

/* Hero Title Sub */
.hero-title-sub {
  font-weight: 400;
  font-size: 0.5em;
  color: var(--text-secondary);
  display: block;
  margin-top: 0.5rem;
}

/* Hero Badges */
.hero-badges {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 1.5rem;
}

.hero-badge {
  padding: 0.5rem 1rem;
  background: var(--surface-translucent, rgba(12, 12, 36, 0.7));
  border: 1px solid var(--border-color);
  border-radius: 999px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

/* Stat Icon */
.stat-icon {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

/* Card Badges & Footer */
.card-badges {
  display: flex;
  gap: 0.4rem;
  align-items: center;
  flex-wrap: wrap;
}

.card-footer {
  padding: 0.6rem 1.25rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.card-stat {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.multi-lang-badge {
  font-size: 0.7rem;
  padding: 0.15rem 0.45rem;
  border-radius: 999px;
  background: rgba(34, 211, 238, 0.1);
  color: var(--accent-tertiary);
  font-weight: 600;
  border: 1px solid rgba(34, 211, 238, 0.2);
}

/* Section Icons */
.section-icon {
  margin-right: 0.4rem;
}

/* Filter Count */
.filter-count {
  font-size: 0.7em;
  opacity: 0.7;
  margin-left: 0.2rem;
}

/* Results Info Bar */
.results-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: var(--container-width, 1200px);
  margin: 0.75rem auto;
  padding: 0 1rem;
  gap: var(--space-4);
  flex-wrap: wrap;
}

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

/* Sort Button */
.sort-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.4rem 0.8rem;
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 0.8rem;
  font-family: var(--font-family, 'Inter', sans-serif);
  transition: all 0.3s ease;
}

.sort-btn:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: rgba(129, 140, 248, 0.05);
}

/* Code Header Details */
.code-header-left {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.code-filename {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-code, 'JetBrains Mono', monospace);
}

.code-lines {
  font-size: 0.7rem;
  color: var(--text-muted);
  padding: 0.15rem 0.5rem;
  background: rgba(255, 255, 255, 0.03);
  border-radius: 4px;
}

/* Complexity Info */
.complexity-info {
  display: flex;
  gap: 1.5rem;
  margin-top: 1rem;
  flex-wrap: wrap;
}

.complexity-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1rem;
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  border-radius: 10px;
}

.complexity-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.complexity-value {
  font-family: var(--font-code, 'JetBrains Mono', monospace);
  font-size: 0.9rem;
  color: var(--accent-tertiary);
  background: rgba(34, 211, 238, 0.08);
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
}

/* Info Value */
.info-value {
  color: var(--text-primary);
  font-size: 0.85rem;
}

/* Problem Nav Arrows */
.nav-arrow {
  font-size: 1.5rem;
  color: var(--accent-primary);
  transition: transform 0.3s ease;
  flex-shrink: 0;
}

.nav-info {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
  min-width: 0;
}


.nav-direction {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.nav-title {
  font-size: 0.9rem;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 300px;
}

/* Footer Links */
.footer-links {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  margin: 0.75rem 0;
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color 0.3s ease;
}

.footer-links a:hover {
  color: var(--accent-primary);
}

/* LeetCode Link (problem page) */
.leetcode-link {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  padding: 0.3rem 0.75rem;
  border-radius: 8px;
  background: rgba(255, 165, 0, 0.08);
  color: #fbbf24;
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 500;
  transition: all 0.3s ease;
  border: 1px solid rgba(255, 165, 0, 0.15);
}

.leetcode-link:hover {
  background: rgba(255, 165, 0, 0.15);
  transform: translateY(-1px);
  border-color: rgba(255, 165, 0, 0.3);
}

/* No Solution State */
.no-solution {
  padding: 2rem;
  text-align: center;
  color: var(--text-muted);
  font-style: italic;
  background: var(--surface-translucent);
  border-radius: 12px;
  border: 1px dashed var(--border-color);
}

.no-solution a {
  color: var(--accent-primary);
}

/* Light theme adjustments for v2 elements */
body.light-theme .hero-orb { opacity: 0.08; }
body.light-theme .hero-badge { background: rgba(255,255,255,0.8); }
body.light-theme .complexity-value { background: rgba(6, 182, 212, 0.08); }
body.light-theme .code-lines { background: rgba(0,0,0,0.04); }
body.light-theme .sort-btn { background: #fff; }

/* --- Pagination --- */
.pagination-container {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: var(--space-2);
  margin-top: var(--space-8);
  flex-wrap: wrap;
}

.page-btn {
  background: var(--surface-translucent);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  font-weight: 500;
  transition: all var(--transition-fast);
  cursor: pointer;
  min-width: 40px;
  display: flex;
  justify-content: center;
}

.page-btn:hover:not(:disabled) {
  border-color: var(--accent-primary);
  color: var(--text-primary);
}

.page-btn.active {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
  color: #fff;
}

.page-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.page-dots {
  color: var(--text-muted);
  padding: 0 var(--space-2);
}

.search-input {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-size: 1rem;
  padding: 0;
  outline: none;
  font-family: inherit;
}
.search-input::placeholder {
  color: var(--text-muted);
}
.search-wrapper {
  transition: box-shadow var(--transition-normal), border-color var(--transition-normal);
}
.search-wrapper:focus-within {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}