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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif;
  font-size: 18px;
  line-height: 1.7;
  color: #1a1a1a;
  background: #f5f5f5;
}

header {
  background: #2c3e50;
  color: #fff;
  text-align: center;
  padding: 40px 20px;
}

.header-inner h1 {
  font-size: 2.5em;
  margin-bottom: 8px;
}

.tagline {
  font-size: 1.15em;
  opacity: 0.9;
}

nav {
  background: #34495e;
  padding: 0 20px;
}

nav ul {
  list-style: none;
  display: flex;
  gap: 0;
  max-width: 900px;
  margin: 0 auto;
}

nav ul li a {
  display: block;
  padding: 14px 24px;
  color: #ecf0f1;
  text-decoration: none;
  font-weight: 600;
  font-size: 16px;
}

nav ul li a:hover,
nav ul li a:focus {
  background: #2c3e50;
  outline: 3px solid #f39c12;
  outline-offset: -3px;
}

nav ul li a[aria-current="page"] {
  background: #2c3e50;
  border-bottom: 3px solid #f39c12;
}

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 30px 20px 50px;
}

section {
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
  padding: 28px 32px;
  margin-bottom: 24px;
}

h2 {
  font-size: 1.4em;
  color: #2c3e50;
  margin-bottom: 16px;
}

h3 {
  font-size: 1.1em;
  color: #34495e;
  margin-top: 20px;
  margin-bottom: 10px;
}

p {
  margin-bottom: 14px;
}

ul, ol {
  margin-bottom: 14px;
  padding-left: 24px;
}

li {
  margin-bottom: 6px;
}

a {
  color: #2980b9;
  text-decoration: underline;
  text-underline-offset: 2px;
}

a:hover,
a:focus {
  color: #1a5276;
  outline: 3px solid #f39c12;
  outline-offset: 2px;
}

.button {
  display: inline-block;
  background: #3498db;
  color: #fff;
  padding: 12px 28px;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 700;
  font-size: 17px;
  border: 2px solid #3498db;
}

.button:hover,
.button:focus {
  background: #2980b9;
  border-color: #2980b9;
  outline: 3px solid #f39c12;
  outline-offset: 2px;
}

.download-button {
  background: #27ae60;
  border-color: #27ae60;
  font-size: 20px;
  padding: 16px 36px;
}

.download-button:hover,
.download-button:focus {
  background: #1e8449;
  border-color: #1e8449;
}

.file-info {
  font-size: 14px;
  color: #7f8c8d;
  margin-top: 6px;
}

code {
  background: #ecf0f1;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 16px;
}

pre {
  background: #ecf0f1;
  padding: 12px;
  border-radius: 4px;
  overflow-x: auto;
}

pre code {
  background: none;
  padding: 0;
}

footer {
  background: #2c3e50;
  color: #ecf0f1;
  text-align: center;
  padding: 20px;
  font-size: 15px;
}

@media (max-width: 600px) {
  header {
    padding: 24px 16px;
  }
  .header-inner h1 {
    font-size: 1.8em;
  }
  nav ul {
    flex-direction: column;
  }
  nav ul li a {
    padding: 12px 16px;
  }
  section {
    padding: 20px;
  }
  .button {
    width: 100%;
    text-align: center;
  }
}