:root {
  color-scheme: light;
  --bg: #f7f8fc;
  --card: #ffffff;
  --text: #181b25;
  --muted: #626a7d;
  --line: #e5e8f0;
  --accent: #3b6bf5;
  --shadow: 0 12px 36px rgba(25, 34, 64, .09);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Roboto", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 0%, rgba(59, 107, 245, .12), transparent 32rem),
    radial-gradient(circle at 90% 100%, rgba(239, 68, 68, .10), transparent 30rem),
    var(--bg);
}

.hub {
  position: relative;
  width: min(680px, calc(100% - 32px));
  margin: 0 auto;
  padding: 56px 0 40px;
}

.hub-theme-toggle {
  position: absolute;
  top: 18px;
  right: 0;
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  color: var(--text);
  background: var(--card);
  box-shadow: var(--shadow);
  cursor: pointer;
}

.hub-theme-toggle:hover,
.hub-theme-toggle:focus-visible {
  border-color: var(--accent);
  color: var(--accent);
  outline: none;
}

.hub-theme-icon { width: 19px; height: 19px; display: block; }

.hero { text-align: center; }

h1 {
  margin: 18px 0 10px;
  font-size: clamp(32px, 7vw, 52px);
  line-height: 1.04;
  letter-spacing: -.04em;
}

.hero p {
  max-width: 540px;
  margin: 0 auto;
  color: var(--muted);
  font-size: 17px;
  line-height: 1.55;
}

.hero-actions {
  display: flex;
  justify-content: center;
  margin-top: 14px;
}

.hero-actions a {
  padding: 8px 12px;
  border-radius: 10px;
  color: var(--accent);
  font-size: 14px;
  font-weight: 700;
  text-decoration: none;
}

.hero-actions a:hover,
.hero-actions a:focus-visible {
  background: color-mix(in srgb, var(--accent) 10%, transparent);
  outline: none;
}

.level-grid {
  display: grid;
  gap: 12px;
  margin-top: 24px;
}

.level-card {
  display: flex;
  align-items: center;
  gap: 16px;
  min-height: 92px;
  padding: 17px 20px;
  color: inherit;
  text-decoration: none;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: var(--shadow);
  transition: transform .18s ease, border-color .18s ease, box-shadow .18s ease;
}

.level-card:hover,
.level-card:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(59, 107, 245, .45);
  box-shadow: 0 16px 42px rgba(25, 34, 64, .13);
  outline: none;
}

.level-badge {
  display: grid;
  place-items: center;
  width: 56px;
  height: 56px;
  flex: 0 0 56px;
  border-radius: 16px;
  color: #fff;
  font-weight: 800;
  letter-spacing: -.02em;
}

.level-a1 .level-badge { background: linear-gradient(135deg, #22b573, #118757); }
.level-a2 .level-badge { background: linear-gradient(135deg, #3b82f6, #3154cf); }
.level-b1 .level-badge { background: linear-gradient(135deg, #8b5cf6, #6737c7); }
.level-b2 .level-badge { background: linear-gradient(135deg, #ef4444, #c42b48); }

.level-copy {
  display: flex;
  flex: 1;
  min-width: 0;
  flex-direction: column;
  gap: 4px;
}

.level-copy strong { font-size: 18px; }
.level-arrow { color: var(--accent); font-size: 24px; }

@media (max-width: 480px) {
  .hub { padding-top: 34px; }
  .level-card { min-height: 82px; padding: 13px 15px; }
  .level-badge { width: 50px; height: 50px; flex-basis: 50px; border-radius: 14px; }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #141519;
  --card: #1d1f24;
  --text: #f4f6fa;
  --muted: #aeb5c3;
  --line: #353943;
  --accent: #7da0ff;
  --shadow: 0 12px 36px rgba(0, 0, 0, .34);
}

:root[data-theme="dark"] body {
  background:
    radial-gradient(circle at 10% 0%, rgba(59, 107, 245, .16), transparent 32rem),
    radial-gradient(circle at 90% 100%, rgba(239, 68, 68, .12), transparent 30rem),
    var(--bg);
}

:root[data-theme="dark"] .level-card:hover,
:root[data-theme="dark"] .level-card:focus-visible {
  border-color: rgba(125, 160, 255, .68);
  box-shadow: 0 16px 42px rgba(0, 0, 0, .42);
}