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

:root {
  --color-bg: #fafafa;
  --color-surface: #ffffff;
  --color-text: #1a1a1a;
  --color-text-secondary: #555555;
  --color-accent: #2d2d2d;
  --color-accent-light: #4a4a4a;
  --color-border: #e0e0e0;
  --color-border-light: #f0f0f0;
  --color-highlight: #0066cc;
  --color-highlight-light: #e8f0fe;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  --max-width: 1100px;
  --radius: 6px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.1);
  --transition: 0.25s ease;
}

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

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-highlight);
  text-decoration: none;
  transition: color var(--transition);
}

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

img {
  max-width: 100%;
  display: block;
}

/* ===== Typography ===== */
h1, h2, h3, h4 {
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-text);
}

h1 { font-size: 2.25rem; letter-spacing: -0.02em; }
h2 { font-size: 1.6rem; letter-spacing: -0.01em; }
h3 { font-size: 1.2rem; }
h4 { font-size: 1rem; }

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

/* ===== Navbar ===== */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(250, 250, 250, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
}

.navbar-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.navbar-logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.navbar-logo:hover {
  color: var(--color-highlight);
}

.navbar-links {
  display: flex;
  gap: 1.8rem;
  list-style: none;
}

.navbar-links a {
  color: var(--color-text-secondary);
  font-size: 0.88rem;
  font-weight: 500;
  transition: color var(--transition);
  position: relative;
}

.navbar-links a:hover,
.navbar-links a.active {
  color: var(--color-text);
}

.navbar-links a.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--color-highlight);
  border-radius: 1px;
}

/* Mobile menu toggle */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.menu-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  margin: 5px 0;
  transition: var(--transition);
}

/* ===== Main Content ===== */
main {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 3rem 2rem;
  width: 100%;
}

/* ===== Page Header ===== */
.page-header {
  margin-bottom: 3rem;
}

.page-header h1 {
  margin-bottom: 0.5rem;
}

.page-header p {
  font-size: 1.05rem;
  max-width: 600px;
}

.page-header .divider {
  width: 48px;
  height: 3px;
  background: var(--color-highlight);
  border-radius: 2px;
  margin-top: 1rem;
}

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--color-border);
  padding: 2rem;
  text-align: center;
}

.footer p {
  font-size: 0.82rem;
  color: var(--color-text-secondary);
  max-width: var(--max-width);
  margin: 0 auto;
}

/* ===== Utility ===== */
.section {
  margin-bottom: 3rem;
}

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

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

.badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.2em 0.65em;
  border-radius: 3px;
  background: var(--color-highlight-light);
  color: var(--color-highlight);
  letter-spacing: 0.02em;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.35rem; }

  .navbar-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: 1rem 2rem;
    gap: 0.8rem;
  }

  .navbar-links.open {
    display: flex;
  }

  .menu-toggle {
    display: block;
  }

  main {
    padding: 2rem 1.25rem;
  }
}

@media (max-width: 480px) {
  h1 { font-size: 1.5rem; }
  main { padding: 1.5rem 1rem; }
}