:root {
  color-scheme: light dark;
  --background: #f5f7fb;
  --surface: rgba(255, 255, 255, 0.9);
  --text: #0f172a;
  --muted: #475569;
  --primary: #2563eb;
  --accent: #0ea5e9;
  --border: rgba(15, 23, 42, 0.08);
}

@media (prefers-color-scheme: dark) {
  :root {
    --background: #0b1220;
    --surface: rgba(15, 23, 41, 0.65);
    --text: #e2e8f0;
    --muted: #94a3b8;
    --border: rgba(148, 163, 184, 0.25);
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Inter", "Segoe UI", sans-serif;
  background: radial-gradient(circle at top, rgba(37, 99, 235, 0.18), transparent 45%),
    radial-gradient(circle at bottom, rgba(14, 165, 233, 0.16), transparent 50%),
    var(--background);
  color: var(--text);
  display: flex;
  flex-direction: column;
}

header {
  padding: 1.75rem 1.5rem 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
}

.brand-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  background: linear-gradient(135deg, #2563eb 0%, #0ea5e9 100%);
  color: #fff;
  font-size: 1rem;
}

.brand a {
  color: inherit;
  text-decoration: none;
}

main {
  width: min(860px, calc(100% - 3rem));
  margin: 2rem auto 0;
  border-radius: 20px;
  background: var(--surface);
  box-shadow: 0 32px 72px rgba(15, 23, 42, 0.18);
  backdrop-filter: blur(12px);
  padding: clamp(2rem, 3vw + 1.75rem, 3.5rem);
  border: 1px solid var(--border);
}

h1 {
  margin-top: 0;
  font-size: clamp(1.9rem, 2.6vw + 1.2rem, 2.6rem);
  letter-spacing: -0.015em;
}

h2 {
  margin-top: 2.75rem;
  margin-bottom: 0.75rem;
  font-size: clamp(1.25rem, 2.2vw + 0.9rem, 1.8rem);
}

h3 {
  margin-top: 1.75rem;
  margin-bottom: 0.35rem;
  font-size: 1.1rem;
}

p,
li,
dd {
  line-height: 1.65;
  color: var(--muted);
  font-size: 1rem;
}

ul {
  padding-left: 1.1rem;
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover,
a:focus {
  text-decoration: underline;
}

.highlight-box {
  margin-top: 1.25rem;
  padding: 1.2rem 1.5rem;
  border-radius: 16px;
  border: 1px solid rgba(37, 99, 235, 0.25);
  background: rgba(37, 99, 235, 0.08);
}

.todo {
  font-weight: 600;
  color: #dc2626;
}

footer {
  margin-top: auto;
  padding: 2.5rem 1.5rem 1.5rem;
  text-align: center;
  color: var(--muted);
  font-size: 0.95rem;
}

@media (max-width: 640px) {
  main {
    width: calc(100% - 2rem);
    margin-top: 1.5rem;
  }

  header {
    padding-left: 1rem;
    padding-right: 1rem;
  }
}