:root {
  color-scheme: light;
  --background: #f6f8fb;
  --surface: #ffffff;
  --text: #162033;
  --muted: #5d6b82;
  --border: #d5e0ec;
  --blue-700: #174a86;
  --blue-600: #1f5fa8;
  --focus: #0b6fbd;
  --shadow: 0 18px 45px rgba(23, 74, 134, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background: var(--background);
}

a {
  color: inherit;
}

a:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 4px;
}

.container {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  padding: 72px 0 36px;
  text-align: center;
}

.level {
  margin: 0;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0;
  color: var(--blue-700);
}

h1,
h2,
h3,
p {
  overflow-wrap: break-word;
}

h1 {
  max-width: 860px;
  margin: 10px auto 0;
  font-size: 3.9rem;
  line-height: 1.05;
  letter-spacing: 0;
}

.subtitle {
  margin: 18px auto 0;
  font-size: 1.5rem;
  font-weight: 650;
  color: var(--blue-700);
}

.intro {
  max-width: 650px;
  margin: 14px auto 0;
  color: var(--muted);
}

.class-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
  padding: 24px 0 72px;
}

.class-card {
  display: flex;
  min-height: 260px;
  flex-direction: column;
  justify-content: space-between;
  gap: 28px;
  padding: 28px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.class-card h3 {
  margin: 14px 0 0;
  font-size: 1.35rem;
  line-height: 1.25;
  letter-spacing: 0;
}

.detail {
  margin: 12px 0 0;
  color: var(--muted);
  font-weight: 600;
}

.card-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  width: 100%;
  padding: 11px 18px;
  border: 2px solid var(--blue-600);
  border-radius: 6px;
  background: var(--blue-600);
  color: #ffffff;
  font-weight: 750;
  text-decoration: none;
}

.card-link:hover {
  background: var(--blue-700);
  border-color: var(--blue-700);
}

.site-footer {
  padding: 22px 0 28px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  text-align: center;
}

.site-footer p {
  margin: 0;
  font-size: 0.95rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 840px) {
  .site-header {
    padding-top: 52px;
  }

  h1 {
    font-size: 2.8rem;
  }

  .class-grid {
    grid-template-columns: 1fr;
    padding-bottom: 48px;
  }

  .class-card {
    min-height: auto;
  }
}

@media (max-width: 520px) {
  .container {
    width: min(100% - 24px, 1120px);
  }

  .site-header {
    padding: 44px 0 28px;
  }

  h1 {
    font-size: 2.3rem;
  }

  .subtitle {
    font-size: 1.2rem;
  }

  .class-card {
    padding: 22px;
  }
}