:root {
  --bg: #ffffff;
  --surface: #ffffff;
  --text: #111111;
  --muted: #6b6b6b;
  --border: #e9e9e9;
  --link: #1a5cff;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
}

.container {
  max-width: 820px;
  margin: 0 auto;
  padding: 28px 20px 48px;
}

header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

header .container {
  padding-top: 18px;
  padding-bottom: 18px;
  display: flex;
  gap: 12px;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
}

.brand {
  font-weight: 600;
  font-size: 18px;
  letter-spacing: 0.1px;
}

nav a {
  margin-right: 14px;
  color: var(--text);
  text-decoration: none;
  font-size: 14px;
}

nav a:last-child {
  margin-right: 0;
}

nav a:hover {
  text-decoration: underline;
}

main {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
}

h1 {
  margin-top: 0;
  font-size: 26px;
}

h2 {
  margin-top: 24px;
  font-size: 18px;
}

p {
  margin: 12px 0;
}

ul {
  margin: 12px 0 12px 20px;
}

a {
  color: var(--link);
}

footer {
  margin-top: 28px;
  color: var(--muted);
  font-size: 13px;
  text-align: center;
}

.note {
  background: #f7f7f7;
  border: 1px solid #e6e6e6;
  padding: 12px 14px;
  border-radius: 8px;
  color: #222222;
  font-size: 14px;
}

@media (max-width: 640px) {
  header .container {
    flex-direction: column;
    align-items: flex-start;
  }

  nav a {
    display: inline-block;
    margin-bottom: 6px;
  }

  main {
    padding: 18px;
  }
}