@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Outfit:wght@500;600;700;800&display=swap');

:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-title: 'Outfit', var(--font-sans);
  
  /* Light Mode Palette */
  --bg-primary: #f8fafc;
  --bg-card: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --accent: #4f46e5;
  --accent-gradient: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
  --border: #e2e8f0;
  --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
  --header-bg: rgba(255, 255, 255, 0.8);
}

@media (prefers-color-scheme: dark) {
  :root {
    /* Dark Mode Palette */
    --bg-primary: #090d16;
    --bg-card: #111827;
    --text-primary: #f9fafb;
    --text-secondary: #9ca3af;
    --text-muted: #6b7280;
    --accent: #818cf8;
    --accent-gradient: linear-gradient(135deg, #818cf8 0%, #34d399 100%);
    --border: #1f2937;
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
    --header-bg: rgba(17, 24, 39, 0.8);
  }
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* Header & Navigation */
header {
  position: sticky;
  top: 0;
  z-index: 10;
  background-color: var(--header-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 1rem 2rem;
  transition: background-color 0.3s, border-color 0.3s;
}

.header-container {
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo-link {
  display: flex;
  align-items: center;
  text-decoration: none;
  gap: 0.75rem;
}

.logo-img {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  object-fit: contain;
}

.logo-text {
  font-family: var(--font-title);
  font-size: 1.35rem;
  font-weight: 700;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  gap: 1.5rem;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.95rem;
  transition: color 0.2s;
}

.nav-links a:hover, .nav-links a.active {
  color: var(--accent);
}

/* Main Container */
.main-layout {
  max-width: 1000px;
  margin: 3rem auto;
  padding: 0 1.5rem;
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

@media (min-width: 850px) {
  .main-layout {
    grid-template-columns: 260px 1fr;
    align-items: start;
  }
}

/* Sidebar / Table of Contents */
.sidebar {
  position: sticky;
  top: 6rem;
  display: none;
}

@media (min-width: 850px) {
  .sidebar {
    display: block;
  }
}

.toc-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.toc-title {
  font-family: var(--font-title);
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 1rem;
  font-weight: 700;
}

.toc-list {
  list-style: none;
}

.toc-item {
  margin-bottom: 0.75rem;
}

.toc-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s, padding-left 0.2s;
  display: block;
}

.toc-link:hover {
  color: var(--accent);
  padding-left: 4px;
}

/* Content Card */
.content-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 24px;
  padding: 2.5rem;
  box-shadow: var(--shadow);
}

.content-header {
  margin-bottom: 2.5rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 1.5rem;
}

.meta-info {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
  font-weight: 500;
  display: flex;
  gap: 1rem;
}

h1 {
  font-family: var(--font-title);
  font-size: 2.25rem;
  font-weight: 800;
  line-height: 1.25;
  margin-bottom: 0.5rem;
  letter-spacing: -0.03em;
}

h2 {
  font-family: var(--font-title);
  font-size: 1.4rem;
  font-weight: 700;
  margin: 2.5rem 0 1rem 0;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--border);
  letter-spacing: -0.01em;
}

h2:first-of-type {
  margin-top: 1rem;
}

p {
  color: var(--text-secondary);
  margin-bottom: 1.25rem;
}

ul, ol {
  margin-bottom: 1.5rem;
  padding-left: 1.5rem;
  color: var(--text-secondary);
}

li {
  margin-bottom: 0.5rem;
}

strong {
  color: var(--text-primary);
}

/* Footer */
footer {
  text-align: center;
  padding: 4rem 2rem;
  border-top: 1px solid var(--border);
  margin-top: 5rem;
}

.footer-container {
  max-width: 1000px;
  margin: 0 auto;
}

.footer-logo {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  margin-bottom: 1rem;
}

.footer-logo .logo-img {
  width: 24px;
  height: 24px;
}

.footer-logo .logo-text {
  font-size: 1.1rem;
}

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

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s;
}

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

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

/* Form Styles */
.form-group {
  margin-bottom: 1.5rem;
  text-align: left;
}

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

.form-control {
  width: 100%;
  padding: 0.85rem 1rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
  outline: none;
}

.form-control:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
  background-color: var(--bg-card);
}

textarea.form-control {
  resize: vertical;
  min-height: 120px;
}

select.form-control {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%2394a3b8'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M19 9l-7 7-7-7'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 1rem center;
  background-size: 1.25rem;
  padding-right: 2.5rem;
}

@media (prefers-color-scheme: dark) {
  select.form-control {
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%236b7280'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M19 9l-7 7-7-7'/%3E%3C/svg%3E");
  }
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  padding: 0.85rem 1.5rem;
  border-radius: 12px;
  border: none;
  background: var(--accent-gradient);
  color: white;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.2s, transform 0.2s;
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}

.btn-primary:hover {
  opacity: 0.95;
  transform: translateY(-1px);
}

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

.btn-primary:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

/* Success / Error States */
.feedback-container {
  display: none;
  text-align: center;
  padding: 2.5rem 1rem;
}

.feedback-icon {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
  font-size: 2rem;
}

.feedback-success {
  background-color: rgba(16, 185, 129, 0.1);
  color: #10b981;
}

.feedback-error {
  background-color: rgba(239, 68, 68, 0.1);
  color: #ef4444;
}

.feedback-title {
  font-family: var(--font-title);
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}

.feedback-message {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 1.5rem;
}

.spinner {
  display: inline-block;
  width: 1.25rem;
  height: 1.25rem;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: white;
  animation: spin 0.8s linear infinite;
  margin-right: 0.5rem;
}

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