:root {
  --bg: #f6f8fb;
  --surface: #ffffff;
  --text: #1f2937;
  --muted: #4b5563;
  --line: #dbe3ef;
  --brand: #0f5bb8;
  --brand-soft: #eaf2ff;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background: linear-gradient(180deg, #eef4ff 0%, var(--bg) 220px, var(--bg) 100%);
  color: var(--text);
  font-family: "Segoe UI", "Avenir Next", -apple-system, BlinkMacSystemFont, sans-serif;
  line-height: 1.6;
}

.container {
  max-width: 920px;
  margin: 0 auto;
  padding: 24px 16px 56px;
}

header {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 20px;
}

h1,
h2,
h3 {
  margin: 0 0 12px;
  line-height: 1.25;
}

h1 {
  font-size: 28px;
}

h2 {
  margin-top: 24px;
  font-size: 20px;
}

p,
li {
  color: var(--text);
}

.small,
.muted {
  color: var(--muted);
  font-size: 14px;
}

nav {
  margin-top: 12px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

nav a,
.btn {
  display: inline-block;
  text-decoration: none;
  border: 1px solid #bcd0f0;
  background: var(--brand-soft);
  color: #0b3e7f;
  border-radius: 10px;
  padding: 8px 12px;
  font-weight: 600;
}

.section {
  margin-top: 16px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 20px;
}

ul,
ol {
  padding-left: 20px;
}

code {
  background: #edf2fb;
  border: 1px solid #d8e3f5;
  border-radius: 6px;
  padding: 1px 5px;
}

footer {
  margin-top: 24px;
  font-size: 14px;
  color: var(--muted);
}

@media (max-width: 640px) {
  h1 {
    font-size: 24px;
  }

  .section,
  header {
    padding: 16px;
  }
}