/* ========================================
   EXCEL FORMULA MAKER - DESIGN SYSTEM
   Premium Glassmorphism UI with Dark/Light Mode
   ======================================== */

/* --- CSS Custom Properties --- */
:root {
  /* Colors - Light Mode */
  --bg-primary: #f0f4f8;
  --bg-secondary: #ffffff;
  --bg-glass: rgba(255, 255, 255, 0.7);
  --bg-glass-hover: rgba(255, 255, 255, 0.85);
  --text-primary: #1a202c;
  --text-secondary: #4a5568;
  --text-muted: #718096;
  --border-color: rgba(0, 0, 0, 0.08);
  --shadow-color: rgba(0, 0, 0, 0.1);

  /* Accent Colors */
  --accent-primary: #10b981;
  --accent-primary-rgb: 16, 185, 129;
  --accent-secondary: #3b82f6;
  --accent-tertiary: #8b5cf6;
  --accent-gradient: linear-gradient(135deg, #10b981 0%, #3b82f6 50%, #8b5cf6 100%);
  --accent-gradient-reverse: linear-gradient(135deg, #8b5cf6 0%, #3b82f6 50%, #10b981 100%);

  /* Category Colors */
  --cat-math: #ef4444;
  --cat-text: #f59e0b;
  --cat-date: #10b981;
  --cat-lookup: #3b82f6;
  --cat-financial: #8b5cf6;
  --cat-statistical: #ec4899;
  --cat-logical: #06b6d4;

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

  /* 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: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Shadows */
  --shadow-sm: 0 2px 8px var(--shadow-color);
  --shadow-md: 0 4px 16px var(--shadow-color);
  --shadow-lg: 0 8px 32px var(--shadow-color);
  --shadow-glow: 0 0 40px rgba(var(--accent-primary-rgb), 0.3);
}

/* Dark Mode */
[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-glass: rgba(30, 41, 59, 0.7);
  --bg-glass-hover: rgba(30, 41, 59, 0.85);
  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --border-color: rgba(255, 255, 255, 0.1);
  --shadow-color: rgba(0, 0, 0, 0.4);
}

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

html {
  scroll-behavior: smooth;
}

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

/* --- Animated Background --- */
.bg-animation {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  overflow: hidden;
}

.bg-animation::before {
  content: '';
  position: absolute;
  width: 150%;
  height: 150%;
  top: -25%;
  left: -25%;
  background:
    radial-gradient(ellipse at 20% 20%, rgba(var(--accent-primary-rgb), 0.15) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 80%, rgba(59, 130, 246, 0.15) 0%, transparent 50%),
    radial-gradient(ellipse at 40% 60%, rgba(139, 92, 246, 0.1) 0%, transparent 50%);
  animation: bgMove 20s ease-in-out infinite;
}

@keyframes bgMove {

  0%,
  100% {
    transform: translate(0, 0) rotate(0deg);
  }

  25% {
    transform: translate(2%, 2%) rotate(1deg);
  }

  50% {
    transform: translate(-1%, 3%) rotate(-1deg);
  }

  75% {
    transform: translate(3%, -2%) rotate(0.5deg);
  }
}

/* --- Typography --- */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-weight: 700;
  line-height: 1.2;
  color: var(--text-primary);
}

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

h2 {
  font-size: clamp(1.5rem, 3vw, 2.25rem);
}

h3 {
  font-size: clamp(1.25rem, 2vw, 1.5rem);
}

p {
  color: var(--text-secondary);
}

/* --- Layout --- */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section {
  padding: var(--space-3xl) 0;
}

/* --- Header --- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: var(--space-md) 0;
  backdrop-filter: blur(20px);
  background: var(--bg-glass);
  border-bottom: 1px solid var(--border-color);
  transition: all var(--transition-base);
}

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

.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 {
  width: 40px;
  height: 40px;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.25rem;
}

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

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.nav-link:hover {
  color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

.theme-toggle {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  border: 2px solid var(--border-color);
  background: var(--bg-glass);
  color: var(--text-primary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
  transform: rotate(15deg);
}

/* --- Hero Section --- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 100px;
  position: relative;
}

.hero-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-3xl);
  align-items: center;
}

.hero-text {
  max-width: 600px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: rgba(var(--accent-primary-rgb), 0.1);
  border: 1px solid rgba(var(--accent-primary-rgb), 0.3);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent-primary);
  margin-bottom: var(--space-lg);
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {

  0%,
  100% {
    opacity: 1;
  }

  50% {
    opacity: 0.7;
  }
}

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

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

.hero-description {
  font-size: 1.125rem;
  margin-bottom: var(--space-xl);
}

.hero-cta {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

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

.btn-primary {
  background: var(--accent-gradient);
  color: white;
  box-shadow: var(--shadow-glow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 0 60px rgba(var(--accent-primary-rgb), 0.4);
}

.btn-secondary {
  background: var(--bg-glass);
  color: var(--text-primary);
  border: 2px solid var(--border-color);
  backdrop-filter: blur(10px);
}

.btn-secondary:hover {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

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

/* --- Glass Card --- */
.glass-card {
  background: var(--bg-glass);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
}

.glass-card:hover {
  background: var(--bg-glass-hover);
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

/* --- AI Chat Section --- */
.ai-section {
  background: var(--bg-secondary);
  border-radius: var(--radius-xl);
  padding: var(--space-2xl);
  margin-top: var(--space-2xl);
}

.ai-header {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.ai-header h2 {
  margin-bottom: var(--space-sm);
}

.ai-chat-container {
  max-width: 900px;
  margin: 0 auto;
}

.ai-mode-tabs {
  display: flex;
  gap: var(--space-sm);
  padding: var(--space-xs);
  background: var(--bg-glass);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-lg);
}

.ai-mode-tab {
  flex: 1;
  padding: var(--space-sm) var(--space-md);
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.ai-mode-tab.active {
  background: var(--accent-gradient);
  color: white;
}

.ai-mode-tab:hover:not(.active) {
  background: var(--bg-glass-hover);
  color: var(--text-primary);
}

.ai-chat-box {
  background: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.ai-messages {
  min-height: 300px;
  max-height: 500px;
  overflow-y: auto;
  padding: var(--space-lg);
}

.ai-message {
  display: flex;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
  animation: fadeIn 0.3s ease;
}

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

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

.ai-message.user {
  flex-direction: row-reverse;
}

.ai-avatar {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  flex-shrink: 0;
}

.ai-avatar.ai {
  background: var(--accent-gradient);
  color: white;
}

.ai-avatar.user {
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
}

.ai-bubble {
  max-width: 80%;
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-lg);
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
}

.ai-message.user .ai-bubble {
  background: var(--accent-gradient);
  color: white;
  border: none;
}

.ai-message.user .ai-bubble p {
  color: white;
}

.formula-result {
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-top: var(--space-md);
  position: relative;
}

.formula-code {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  color: var(--accent-primary);
  word-break: break-all;
}

.copy-btn {
  position: absolute;
  top: var(--space-sm);
  right: var(--space-sm);
  padding: var(--space-xs) var(--space-sm);
  font-size: 0.75rem;
  background: var(--accent-primary);
  color: white;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.formula-result:hover .copy-btn {
  opacity: 1;
}

.copy-btn:hover {
  background: var(--accent-secondary);
}

.ai-input-container {
  display: flex;
  gap: var(--space-md);
  padding: var(--space-lg);
  border-top: 1px solid var(--border-color);
  background: var(--bg-secondary);
}

.ai-input {
  flex: 1;
  padding: var(--space-md) var(--space-lg);
  font-family: inherit;
  font-size: 1rem;
  background: var(--bg-glass);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  transition: all var(--transition-fast);
  resize: none;
}

.ai-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 4px rgba(var(--accent-primary-rgb), 0.1);
}

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

.ai-send-btn {
  width: 50px;
  height: 50px;
  border-radius: var(--radius-md);
  background: var(--accent-gradient);
  border: none;
  color: white;
  font-size: 1.25rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.ai-send-btn:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-glow);
}

.ai-send-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Loading Animation */
.typing-indicator {
  display: flex;
  gap: 4px;
  padding: var(--space-md);
}

.typing-dot {
  width: 8px;
  height: 8px;
  background: var(--accent-primary);
  border-radius: 50%;
  animation: typing 1.4s infinite;
}

.typing-dot:nth-child(2) {
  animation-delay: 0.2s;
}

.typing-dot:nth-child(3) {
  animation-delay: 0.4s;
}

@keyframes typing {

  0%,
  60%,
  100% {
    transform: translateY(0);
    opacity: 0.4;
  }

  30% {
    transform: translateY(-8px);
    opacity: 1;
  }
}

/* --- Formula Library Section --- */
.library-section {
  padding: var(--space-3xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.section-header p {
  max-width: 600px;
  margin: var(--space-md) auto 0;
}

.library-search {
  max-width: 500px;
  margin: 0 auto var(--space-xl);
  position: relative;
}

.library-search input {
  width: 100%;
  padding: var(--space-md) var(--space-lg);
  padding-left: 50px;
  font-family: inherit;
  font-size: 1rem;
  background: var(--bg-glass);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-full);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.library-search input:focus {
  outline: none;
  border-color: var(--accent-primary);
}

.library-search-icon {
  position: absolute;
  left: var(--space-lg);
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
}

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

.category-tab {
  padding: var(--space-sm) var(--space-lg);
  border: 2px solid var(--border-color);
  background: var(--bg-glass);
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.category-tab:hover,
.category-tab.active {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

.category-tab[data-category="math"] {
  --cat-color: var(--cat-math);
}

.category-tab[data-category="text"] {
  --cat-color: var(--cat-text);
}

.category-tab[data-category="date"] {
  --cat-color: var(--cat-date);
}

.category-tab[data-category="lookup"] {
  --cat-color: var(--cat-lookup);
}

.category-tab[data-category="financial"] {
  --cat-color: var(--cat-financial);
}

.category-tab[data-category="statistical"] {
  --cat-color: var(--cat-statistical);
}

.category-tab[data-category="logical"] {
  --cat-color: var(--cat-logical);
}

.category-tab[data-category]:hover,
.category-tab[data-category].active {
  border-color: var(--cat-color);
  color: var(--cat-color);
  background: color-mix(in srgb, var(--cat-color) 10%, transparent);
}

.formula-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: var(--space-lg);
}

.formula-card {
  background: var(--bg-glass);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

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

.formula-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--card-accent, var(--accent-primary));
}

.formula-card[data-category="math"] {
  --card-accent: var(--cat-math);
}

.formula-card[data-category="text"] {
  --card-accent: var(--cat-text);
}

.formula-card[data-category="date"] {
  --card-accent: var(--cat-date);
}

.formula-card[data-category="lookup"] {
  --card-accent: var(--cat-lookup);
}

.formula-card[data-category="financial"] {
  --card-accent: var(--cat-financial);
}

.formula-card[data-category="statistical"] {
  --card-accent: var(--cat-statistical);
}

.formula-card[data-category="logical"] {
  --card-accent: var(--cat-logical);
}

.formula-card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-md);
}

.formula-name {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.formula-category-badge {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--card-accent) 15%, transparent);
  color: var(--card-accent);
}

.formula-description {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-md);
}

.formula-syntax {
  background: var(--bg-primary);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent-primary);
  margin-bottom: var(--space-md);
  overflow-x: auto;
}

.formula-example {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.formula-example strong {
  color: var(--text-secondary);
}

.formula-card-actions {
  display: flex;
  gap: var(--space-sm);
  margin-top: var(--space-md);
  padding-top: var(--space-md);
  border-top: 1px solid var(--border-color);
}

.formula-action-btn {
  flex: 1;
  padding: var(--space-sm);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  border: 1px solid var(--border-color);
  background: transparent;
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
}

.formula-action-btn:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

.formula-action-btn.copied {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
  color: white;
}

/* --- Formula Builder Section --- */
.builder-section {
  background: var(--bg-secondary);
  padding: var(--space-3xl) 0;
}

.builder-container {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: var(--space-xl);
  max-width: 1200px;
  margin: 0 auto;
}

.builder-sidebar {
  background: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  height: fit-content;
  position: sticky;
  top: 100px;
}

.builder-sidebar h3 {
  margin-bottom: var(--space-md);
  font-size: 1rem;
}

.function-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  max-height: 400px;
  overflow-y: auto;
}

.function-item {
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  cursor: grab;
  transition: all var(--transition-fast);
}

.function-item:hover {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

.function-item:active {
  cursor: grabbing;
}

.builder-main {
  background: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
}

.builder-preview {
  background: var(--bg-primary);
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--space-xl);
  min-height: 120px;
  font-family: var(--font-mono);
  font-size: 1.25rem;
  color: var(--accent-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  margin-bottom: var(--space-lg);
  transition: all var(--transition-fast);
}

.builder-preview.drag-over {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.05);
}

.builder-preview.has-content {
  justify-content: flex-start;
  padding: var(--space-lg);
}

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

/* --- Features Section --- */
.features-section {
  padding: var(--space-3xl) 0;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
}

.feature-card {
  text-align: center;
  padding: var(--space-xl);
}

.feature-icon {
  width: 70px;
  height: 70px;
  margin: 0 auto var(--space-lg);
  background: var(--accent-gradient);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  color: white;
  box-shadow: var(--shadow-glow);
}

.feature-card h3 {
  margin-bottom: var(--space-md);
}

/* --- Footer --- */
.footer {
  background: var(--bg-secondary);
  padding: var(--space-2xl) 0;
  text-align: center;
  border-top: 1px solid var(--border-color);
}

.footer-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-lg);
}

.footer-logo {
  font-size: 1.25rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

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

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

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

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

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

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

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

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

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

/* --- Responsive --- */
@media (max-width: 1024px) {
  .hero-content {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .hero-cta {
    justify-content: center;
  }

  .builder-container {
    grid-template-columns: 1fr;
  }

  .builder-sidebar {
    position: static;
  }
}

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

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
  }

  .nav-link {
    display: none;
  }

  .hero {
    padding-top: 120px;
  }

  .hero-cta {
    flex-direction: column;
    align-items: stretch;
  }

  .ai-mode-tabs {
    flex-wrap: wrap;
  }

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

  .category-tabs {
    flex-wrap: nowrap;
    overflow-x: auto;
    justify-content: flex-start;
    padding-bottom: var(--space-sm);
    -webkit-overflow-scrolling: touch;
  }

  .category-tab {
    flex-shrink: 0;
  }
}

/* --- Toast Notifications --- */
.toast-container {
  position: fixed;
  bottom: var(--space-xl);
  right: var(--space-xl);
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.toast {
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: var(--space-md);
  animation: slideIn 0.3s ease;
  min-width: 280px;
}

.toast.success {
  border-color: var(--accent-primary);
}

.toast.error {
  border-color: var(--cat-math);
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(100%);
  }

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

.toast-icon {
  font-size: 1.25rem;
}

.toast.success .toast-icon {
  color: var(--accent-primary);
}

.toast.error .toast-icon {
  color: var(--cat-math);
}

.toast-message {
  flex: 1;
  font-size: 0.9rem;
}

/* --- Empty State --- */
.empty-state {
  text-align: center;
  padding: var(--space-3xl);
  color: var(--text-muted);
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: var(--space-md);
  opacity: 0.5;
}

/* ========================================
   EXCEL EDITOR SECTION
   ======================================== */

/* --- Editor Container --- */
.editor-section {
  background: var(--bg-secondary);
  padding: var(--space-3xl) 0;
}

.editor-container {
  background: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

/* --- File Upload Zone --- */
.upload-zone {
  padding: var(--space-2xl);
  border: 3px dashed var(--border-color);
  border-radius: var(--radius-lg);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-base);
  margin: var(--space-xl);
  background: var(--bg-primary);
}

.upload-zone:hover,
.upload-zone.drag-over {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.05);
}

.upload-zone.drag-over {
  transform: scale(1.01);
}

.upload-zone-icon {
  font-size: 4rem;
  margin-bottom: var(--space-md);
  opacity: 0.7;
}

.upload-zone h3 {
  margin-bottom: var(--space-sm);
  color: var(--text-primary);
}

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

.upload-zone-formats {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  margin-top: var(--space-md);
}

.upload-format-badge {
  padding: var(--space-xs) var(--space-sm);
  background: rgba(var(--accent-primary-rgb), 0.1);
  color: var(--accent-primary);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
}

.upload-zone input[type="file"] {
  display: none;
}

/* --- Spreadsheet Container --- */
.spreadsheet-wrapper {
  display: none;
  flex-direction: column;
  height: 600px;
}

.spreadsheet-wrapper.active {
  display: flex;
}

/* --- Toolbar --- */
.spreadsheet-toolbar {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  flex-wrap: wrap;
}

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

.toolbar-divider {
  width: 1px;
  height: 24px;
  background: var(--border-color);
  margin: 0 var(--space-sm);
}

.toolbar-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-color);
  background: var(--bg-glass);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 1rem;
}

.toolbar-btn:hover {
  border-color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

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

/* --- Cell Reference & Formula Bar --- */
.cell-reference {
  width: 80px;
  padding: var(--space-sm);
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-primary);
  text-align: center;
}

.formula-bar {
  flex: 1;
  min-width: 200px;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
}

.formula-bar-label {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text-muted);
  font-weight: 600;
}

.formula-bar-input {
  flex: 1;
  border: none;
  background: transparent;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--accent-primary);
  outline: none;
}

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

/* --- Spreadsheet Grid --- */
.spreadsheet-container {
  flex: 1;
  overflow: auto;
  position: relative;
  background: var(--bg-primary);
}

.spreadsheet-table {
  border-collapse: collapse;
  min-width: 100%;
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.spreadsheet-table th,
.spreadsheet-table td {
  border: 1px solid var(--border-color);
  padding: 0;
  min-width: 100px;
  height: 28px;
  position: relative;
}

.spreadsheet-table th {
  background: var(--bg-secondary);
  font-weight: 600;
  color: var(--text-secondary);
  position: sticky;
  top: 0;
  z-index: 10;
  user-select: none;
}

.spreadsheet-table th:first-child {
  left: 0;
  z-index: 20;
  min-width: 50px;
  width: 50px;
}

.spreadsheet-table td:first-child {
  background: var(--bg-secondary);
  font-weight: 600;
  color: var(--text-secondary);
  text-align: center;
  position: sticky;
  left: 0;
  z-index: 5;
  min-width: 50px;
  width: 50px;
}

.spreadsheet-cell {
  width: 100%;
  height: 100%;
  padding: 4px 8px;
  border: none;
  background: transparent;
  font-family: inherit;
  font-size: inherit;
  color: var(--text-primary);
  outline: none;
  box-sizing: border-box;
}

.spreadsheet-cell:focus {
  background: var(--bg-glass);
  box-shadow: inset 0 0 0 2px var(--accent-primary);
}

.spreadsheet-cell.formula {
  color: var(--accent-primary);
}

.spreadsheet-cell.selected {
  background: rgba(var(--accent-primary-rgb), 0.1);
}

/* --- Sheet Tabs --- */
.sheet-tabs {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-lg);
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  overflow-x: auto;
}

.sheet-tab {
  padding: var(--space-sm) var(--space-lg);
  background: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-bottom: none;
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  font-family: inherit;
  font-size: 0.85rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.sheet-tab:hover {
  background: var(--bg-glass-hover);
  color: var(--text-primary);
}

.sheet-tab.active {
  background: var(--bg-primary);
  color: var(--accent-primary);
  border-color: var(--accent-primary);
  font-weight: 600;
}

.sheet-tab-add {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.sheet-tab-add:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: rgba(var(--accent-primary-rgb), 0.1);
}

/* --- File Info Bar --- */
.file-info-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-glass);
  border-bottom: 1px solid var(--border-color);
}

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

.file-name {
  font-weight: 600;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.file-size {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.file-actions {
  display: flex;
  gap: var(--space-sm);
}

/* --- Insert Formula from AI Button --- */
.insert-formula-btn {
  position: fixed;
  bottom: var(--space-xl);
  left: 50%;
  transform: translateX(-50%);
  z-index: 100;
  display: none;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-xl);
  background: var(--accent-gradient);
  color: white;
  border: none;
  border-radius: var(--radius-full);
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-glow), var(--shadow-lg);
  transition: all var(--transition-fast);
}

.insert-formula-btn.visible {
  display: flex;
  animation: fadeIn 0.3s ease;
}

.insert-formula-btn:hover {
  transform: translateX(-50%) scale(1.05);
}

/* --- Responsive for Editor --- */
@media (max-width: 768px) {
  .spreadsheet-toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .toolbar-group {
    justify-content: center;
  }

  .formula-bar {
    min-width: 100%;
  }

  .cell-reference {
    width: 100%;
    text-align: left;
  }
}