:root {
  --color-primary: #2563EB;
  --color-secondary: #0F172A;
  --color-bg: #ffffff;
  --color-text: #171717;
  --color-muted: #6B7280;
  --color-border: #E5E7EB;
  --color-card: #F9FAFB;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --transition: 200ms ease;
  --max-width: 1200px;
  --font-sans: "Inter", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition), opacity var(--transition);
}

a:hover {
  color: #1d4ed8;
}

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

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  height: 64px;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: 16px;
}

.brand {
  font-weight: 700;
  color: var(--color-secondary);
  font-size: 20px;
  letter-spacing: -0.02em;
}

.nav {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 14px;
}

.nav a {
  color: var(--color-secondary);
  font-weight: 500;
}

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

.header-search {
  flex: 1;
  max-width: 520px;
  position: relative;
}

.search-input {
  width: 100%;
  border: 1px solid var(--color-border);
  background: #fff;
  padding: 12px 16px;
  border-radius: 999px;
  font-size: 15px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.hero {
  padding: 64px 0 32px;
  text-align: center;
}

.hero h1 {
  color: var(--color-secondary);
  font-size: 40px;
  line-height: 1.2;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.hero p {
  color: var(--color-muted);
  max-width: 700px;
  margin: 0 auto 24px;
  font-size: 18px;
}

.hero-search {
  max-width: 680px;
  margin: 0 auto;
}

.hero .search-input {
  font-size: 16px;
  padding: 16px 20px;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
  margin-top: 16px;
}

.chip {
  padding: 6px 12px;
  background: #EEF2FF;
  color: var(--color-primary);
  border-radius: 999px;
  font-size: 13px;
  font-weight: 500;
  transition: background var(--transition), color var(--transition);
}

.chip:hover {
  background: var(--color-primary);
  color: #fff;
}

.section {
  padding: 32px 0;
}

.section-title {
  font-size: 22px;
  color: var(--color-secondary);
  margin-bottom: 16px;
}

.grid {
  display: grid;
  gap: 18px;
}

.grid-3 {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.grid-4 {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 18px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: #dbe1ea;
}

.card-icon {
  width: 32px;
  height: 32px;
  margin-bottom: 10px;
  color: var(--color-primary);
}

.card-title {
  color: var(--color-secondary);
  font-weight: 600;
  margin-bottom: 6px;
}

.card-text {
  color: var(--color-muted);
  font-size: 14px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--color-primary);
  color: #fff;
  border: none;
  border-radius: 999px;
  padding: 10px 18px;
  font-weight: 600;
  font-size: 14px;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition);
}

.button:hover {
  background: #1d4ed8;
  transform: translateY(-1px);
}

.button-outline {
  background: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}

.button-outline:hover {
  background: var(--color-primary);
  color: #fff;
}

.page {
  padding: 32px 0 56px;
}

.two-col {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 24px;
  align-items: start;
}

.resource-card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 18px;
  margin-bottom: 16px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), border-color var(--transition);
}

.resource-card:hover {
  box-shadow: var(--shadow-md);
  border-color: #dbe1ea;
}

.resource-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
}

.resource-thumb {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--color-card);
  border: 1px solid var(--color-border);
}

.resource-title {
  color: var(--color-secondary);
  font-weight: 600;
}

.resource-desc {
  color: var(--color-muted);
  font-size: 14px;
  margin: 6px 0 10px;
}

.badges {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 10px;
}

.badge {
  background: #EEF2FF;
  color: var(--color-primary);
  border-radius: 999px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 500;
}

.meta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  font-size: 12px;
  color: var(--color-muted);
}

.aside-box {
  position: sticky;
  top: 88px;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 16px;
}

.toc {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc li {
  margin: 8px 0;
}

.toc a {
  color: var(--color-secondary);
  font-size: 14px;
}

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

.footer {
  border-top: 1px solid var(--color-border);
  padding: 24px 0;
  color: var(--color-muted);
  font-size: 14px;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-top: 10px;
}

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

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

@media (max-width: 1024px) {
  .grid-4 {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  .two-col {
    grid-template-columns: 1fr;
  }
  .aside-box {
    position: static;
  }
}

@media (max-width: 768px) {
  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding: 10px 0;
  }
  .header-search {
    order: 1;
    width: 100%;
    max-width: none;
  }
  .nav {
    order: 2;
    width: 100%;
    justify-content: space-between;
  }
  .hero h1 {
    font-size: 30px;
  }
  .grid-4,
  .grid-3 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 480px) {
  .grid-4,
  .grid-3 {
    grid-template-columns: 1fr;
  }
  .hero {
    padding: 40px 0 20px;
  }
  .hero h1 {
    font-size: 26px;
  }
  .hero p {
    font-size: 16px;
  }
  .search-input {
    padding: 12px 14px;
  }
}