:root {
  --bg: #081420;
  --panel-border: #2c4864;
  --text: #f3f7fa;
  --muted: #9eb2c4;
  --radius: 14px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "IBM Plex Sans", sans-serif;
  color: var(--text);
  background: var(--bg);
}

.bg-layer {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(circle at 8% 15%, #164667 0%, transparent 36%),
    radial-gradient(circle at 78% 12%, #3d2c5f 0%, transparent 30%),
    radial-gradient(circle at 26% 92%, #1b4d45 0%, transparent 32%),
    linear-gradient(145deg, #07111b 0%, #0f2235 55%, #091523 100%);
}

h1,
h2,
h3,
h4 {
  font-family: "Space Grotesk", sans-serif;
}

.topbar {
  max-width: 1400px;
  margin: 0 auto;
  padding: 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
}

.topbar h1 {
  margin: 0;
  font-size: clamp(1.3rem, 2.5vw, 1.8rem);
}

.brand-line {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.brand-subtitle {
  margin: 0;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 500;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.page-link {
  border: 1px solid #41729f;
  border-radius: 10px;
  background: #1a3551;
  color: #e9f4ff;
  text-decoration: none;
  padding: 7px 11px;
  font-size: 0.85rem;
  font-weight: 600;
}

.page-link.active {
  background: #285782;
}

.github-icon-link {
  width: 34px;
  height: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid rgb(67 101 131 / 78%);
  border-radius: 10px;
  background: rgb(15 33 49 / 72%);
  color: #b7c8d8;
  text-decoration: none;
  transition: background 130ms ease, border-color 130ms ease, color 130ms ease, transform 130ms ease;
}

.github-icon-link svg {
  width: 16px;
  height: 16px;
  fill: currentColor;
}

.github-icon-link:hover,
.github-icon-link:focus-visible {
  background: rgb(25 50 73 / 82%);
  border-color: rgb(98 132 166 / 88%);
  color: #dbe9f7;
  transform: translateY(-1px);
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 6px 20px 32px;
  display: grid;
  gap: 12px;
}

.panel {
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  background: linear-gradient(170deg, rgb(12 29 45 / 90%), rgb(10 21 33 / 94%));
  padding: 14px;
}

.panel h2,
.panel h3,
.panel h4 {
  margin-top: 0;
}

.panel p {
  margin: 0;
  color: #ccdae7;
}

.intro p {
  font-size: 1rem;
  line-height: 1.45;
}

.muted {
  color: var(--muted) !important;
  margin-bottom: 10px !important;
}

.pill-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.pill {
  border: 1px solid var(--panel-border);
  border-radius: 999px;
  padding: 5px 10px;
  color: #dce9f7;
  font-size: 0.84rem;
  background: rgb(9 21 34 / 80%);
}

.list {
  margin: 0;
  padding-left: 18px;
  display: grid;
  gap: 8px;
  color: #d4e2f1;
}

.list li {
  line-height: 1.35;
}

.levels {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.level {
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  padding: 10px;
  background: rgb(9 21 34 / 80%);
}

.level h4 {
  margin-bottom: 6px;
}

.level p {
  font-size: 0.92rem;
}

.level-foundational {
  border-color: #8d7a2d;
}

.level-intermediate {
  border-color: #2f8d79;
}

.level-advanced {
  border-color: #446fba;
}

.level-expert {
  border-color: #a55a52;
}

.footer-note a {
  color: #9de5ff;
}

@media (max-width: 920px) {
  .levels {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .topbar {
    flex-direction: column;
    align-items: flex-start;
  }

  .nav-links {
    width: 100%;
  }
}