:root {
  --bg: #f6f8fb;
  --surface: #ffffff;
  --ink: #12233d;
  --muted: #5f6f87;
  --line: #d8dfeb;
  --brand: #1f6feb;
  --brand-ink: #ffffff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Avenir Next", "Segoe UI", sans-serif;
  color: var(--ink);
  background: radial-gradient(circle at 10% 10%, #eef5ff 0%, var(--bg) 45%);
  line-height: 1.6;
}

main {
  max-width: 860px;
  margin: 0 auto;
  padding: 2.5rem 1.25rem 4rem;
}

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

.nav {
  max-width: 860px;
  margin: 0 auto;
  padding: 1rem 1.25rem;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: center;
}

.brand {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
}

.links {
  display: flex;
  gap: 0.9rem;
  flex-wrap: wrap;
}

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

.links a {
  text-decoration: none;
  color: var(--muted);
  font-size: 0.95rem;
}

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

h1 {
  line-height: 1.2;
}

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 1rem 1.1rem;
  margin: 1rem 0;
}

.btn {
  display: inline-block;
  background: var(--brand);
  color: var(--brand-ink);
  text-decoration: none;
  padding: 0.65rem 1rem;
  border-radius: 10px;
  font-weight: 600;
  margin-top: 0.6rem;
}

.note {
  color: var(--muted);
  font-size: 0.95rem;
}

ul {
  padding-left: 1.2rem;
}

footer {
  margin-top: 2.5rem;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 640px) {
  main {
    padding-top: 2rem;
  }

  .nav {
    align-items: flex-start;
    flex-direction: column;
  }
}