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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: #f1f5f9;
  background: #0f172a;
  display: flex;
  min-height: 100vh;
}

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  height: 100vh;
  background: #1e293b;
  border-right: 1px solid #334155;
  overflow-y: auto;
  padding: 40px 20px;
}

.nav-header {
  font-weight: bold;
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: #94a3b8;
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 1px solid #334155;
}

.sidebar nav ul {
  list-style: none;
}

.sidebar nav li {
  margin-bottom: 12px;
}

.sidebar nav a {
  color: #cbd5e1;
  text-decoration: none;
  font-size: 14px;
  line-height: 1.4;
  display: block;
  padding: 4px 0;
  transition: color 0.2s;
}

.sidebar nav a:hover {
  color: #f1f5f9;
}

main {
  margin-left: 280px;
  flex: 1;
  padding: 60px 40px;
  max-width: 900px;
}

article {
  background: #1e293b;
  padding: 60px;
  border: 1px solid #334155;
}

header {
  margin-bottom: 40px;
  padding-bottom: 30px;
  border-bottom: 1px solid #334155;
}

h1 {
  font-size: 2.5rem;
  font-weight: bold;
  line-height: 1.2;
  color: #f1f5f9;
  letter-spacing: -0.02em;
  margin-bottom: 0;
}

h2 {
  font-size: 1.75rem;
  font-weight: bold;
  line-height: 1.3;
  color: #f1f5f9;
  margin-top: 50px;
  margin-bottom: 20px;
  padding-top: 30px;
  border-top: 1px solid #334155;
  letter-spacing: -0.01em;
}

section:first-of-type h2 {
  margin-top: 0;
  padding-top: 0;
  border-top: none;
}

.intro {
  margin-bottom: 40px;
}

p {
  margin-bottom: 20px;
  color: #cbd5e1;
}

section {
  margin-bottom: 30px;
}

ul {
  list-style: none;
  margin-bottom: 20px;
}

ul li {
  margin-bottom: 15px;
  padding-left: 0;
  color: #cbd5e1;
}

a {
  color: #60a5fa;
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s;
}

a:hover {
  border-bottom-color: #60a5fa;
}

strong {
  color: #f1f5f9;
  font-weight: bold;
}

@media (max-width: 1024px) {
  .sidebar {
    width: 240px;
  }

  main {
    margin-left: 240px;
  }

  article {
    padding: 40px;
  }
}

@media (max-width: 768px) {
  body {
    flex-direction: column;
  }

  .sidebar {
    position: static;
    width: 100%;
    height: auto;
    border-right: none;
    border-bottom: 1px solid #334155;
  }

  main {
    margin-left: 0;
    padding: 30px 20px;
  }

  article {
    padding: 30px 20px;
  }

  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.5rem;
  }
}