:root {
  /* Color Palette - Light Mode */
  --primary-color: #4F46E5;
  --primary-hover: #4338CA;
  --secondary-color: #10B981;
  --accent-color: #F59E0B;

  --bg-color: #F9FAFB;
  --card-bg: #FFFFFF;
  --text-main: #111827;
  --text-muted: #6B7280;
  --border-color: #E5E7EB;

  --input-bg: #FFFFFF;
  --input-border: #D1D5DB;

  /* Spacing & Layout */
  --container-width: 1200px;
  --header-height: 70px;
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 1rem;

  /* 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);
}

[data-theme="dark"] {
  --primary-color: #6366F1;
  --primary-hover: #818CF8;

  --bg-color: #111827;
  --card-bg: #1F2937;
  --text-main: #F9FAFB;
  --text-muted: #9CA3AF;
  --border-color: #374151;

  --input-bg: #374151;
  --input-border: #4B5563;
}

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

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.5;
  transition: background-color 0.3s ease, color 0.3s ease;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

main {
  flex: 1;
}

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

ul {
  list-style: none;
}

/* Layout Utilities */
.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 1rem;
}

.grid {
  display: grid;
  gap: 1.5rem;
}

.flex {
  display: flex;
}

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

.justify-between {
  justify-content: space-between;
}

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

.gap-2 {
  gap: 0.5rem;
}

.gap-4 {
  gap: 1rem;
}

.gap-6 {
  gap: 1.5rem;
}

.gap-8 {
  gap: 2rem;
}

/* Components */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
  font-size: 1rem;
}

.btn-primary {
  background-color: var(--primary-color);
  color: white;
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

.btn-outline {
  background-color: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-main);
}

.btn-outline:hover {
  background-color: var(--border-color);
}

.card {
  background-color: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: 1.5rem;
  border: 1px solid var(--border-color);
  transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.input-group {
  margin-bottom: 1rem;
}

.input-label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  color: var(--text-main);
}

.form-control {
  width: 100%;
  padding: 0.75rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--input-border);
  background-color: var(--input-bg);
  color: var(--text-main);
  font-size: 1rem;
  transition: border-color 0.2s;
}

.form-control:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* Header */
.site-header {
  height: var(--header-height);
  background-color: rgba(255, 255, 255, 0.95);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: background-color 0.3s, border-color 0.3s, box-shadow 0.3s;
}

.site-header.scrolled {
  box-shadow: var(--shadow-md);
}

[data-theme="dark"] .site-header {
  background-color: rgba(17, 24, 39, 0.95);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary-color);
  letter-spacing: -0.025em;
  transition: transform 0.2s;
}

.logo:hover {
  transform: scale(1.05);
}

.logo-icon {
  font-size: 1.75rem;
}

.main-nav {
  display: flex;
  gap: 2rem;
}

.nav-link {
  color: var(--text-muted);
  font-weight: 500;
  text-decoration: none;
  transition: color 0.2s;
  font-size: 0.95rem;
  position: relative;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--primary-color);
  transition: width 0.3s;
}

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

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

.header-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.btn-icon {
  background: none;
  border: none;
  color: var(--text-main);
  cursor: pointer;
  padding: 0.5rem;
  border-radius: var(--radius-md);
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.btn-icon:hover {
  background-color: var(--bg-color);
  color: var(--primary-color);
  transform: scale(1.1);
}

.mobile-only {
  display: none;
}

/* Mobile Menu */
@media (max-width: 768px) {
  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: 100%;
    background-color: var(--card-bg);
    flex-direction: column;
    padding: 1rem;
    gap: 0.5rem;
    border-bottom: 1px solid var(--border-color);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease-in-out;
    z-index: 90;
    box-shadow: var(--shadow-lg);
  }

  .main-nav.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-link {
    padding: 1rem;
    border-radius: var(--radius-md);
    display: block;
  }

  .nav-link::after {
    display: none;
  }

  .nav-link:hover {
    background-color: var(--bg-color);
  }

  .mobile-only {
    display: flex;
  }
}

/* Hero Section */
.hero {
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: radial-gradient(var(--primary-color) 1px, transparent 1px);
  background-size: 20px 20px;
  opacity: 0.05;
  z-index: -1;
}

/* Footer */
.site-footer {
  background-color: var(--card-bg);
  border-top: 1px solid var(--border-color);
  padding: 3rem 0 1.5rem;
  margin-top: 4rem;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--text-muted);
  font-size: 0.875rem;
  transition: color 0.2s;
}

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

.footer-bottom {
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 0.875rem;
}

/* Utilities */
.text-center {
  text-align: center;
}

.mt-4 {
  margin-top: 1rem;
}

.mt-6 {
  margin-top: 1.5rem;
}

.mt-8 {
  margin-top: 2rem;
}

.mb-4 {
  margin-bottom: 1rem;
}

.mb-6 {
  margin-bottom: 1.5rem;
}

.mb-8 {
  margin-bottom: 2rem;
}

.text-xl {
  font-size: 1.25rem;
}

.text-2xl {
  font-size: 1.5rem;
}

.text-3xl {
  font-size: 1.875rem;
}

.text-4xl {
  font-size: 2.25rem;
}

.font-bold {
  font-weight: 700;
}

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