:root {
  --bg: #07111b;
  --panel: rgba(9, 20, 34, 0.84);
  --line: rgba(150, 201, 255, 0.14);
  --text: #edf7ff;
  --muted: #adc3d8;
  --accent: #86e7ff;
  --accent-strong: #25bfff;
  --energy: #ffd16f;
  --shadow: 0 26px 70px rgba(0, 0, 0, 0.34);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Space Grotesk", "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 8% 0%, rgba(37, 191, 255, 0.18), transparent 28%),
    radial-gradient(circle at 90% 14%, rgba(255, 209, 111, 0.14), transparent 20%),
    linear-gradient(165deg, #030910 0%, #091523 40%, #112740 100%);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.16;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px);
  background-size: 36px 36px;
}

.page {
  width: min(1180px, calc(100vw - 2rem));
  margin: 0 auto;
  padding: 2rem 0 3rem;
}

.site-nav {
  display: flex;
  gap: 0.65rem;
  flex-wrap: wrap;
  align-items: center;
  margin-bottom: 1rem;
  padding: 0.7rem;
  border-radius: 20px;
  border: 1px solid var(--line);
  background: rgba(9, 20, 34, 0.68);
  backdrop-filter: blur(12px);
  box-shadow: var(--shadow);
}

.nav-brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  margin-right: auto;
  padding: 0.3rem 0.35rem 0.3rem 0.1rem;
  text-decoration: none;
  color: var(--text);
  font-weight: 800;
  letter-spacing: 0.04em;
}

.brand-mark {
  position: relative;
  width: 34px;
  height: 34px;
  display: inline-block;
}

.brand-core,
.brand-orbit {
  position: absolute;
  inset: 0;
}

.brand-core {
  width: 8px;
  height: 8px;
  inset: 50% auto auto 50%;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  background: linear-gradient(135deg, var(--energy), var(--accent));
  box-shadow: 0 0 18px rgba(134, 231, 255, 0.45);
  animation: core-pulse 2.8s ease-in-out infinite;
}

.brand-orbit {
  border: 2px solid rgba(134, 231, 255, 0.72);
  border-radius: 50%;
}

.orbit-a {
  transform: rotate(28deg) scaleX(1.18) scaleY(0.58);
  animation: orbit-spin-a 7s linear infinite;
}

.orbit-b {
  transform: rotate(-28deg) scaleX(1.18) scaleY(0.58);
  animation: orbit-spin-b 9s linear infinite;
}

.brand-text {
  font-size: 0.95rem;
}

@keyframes orbit-spin-a {
  from {
    transform: rotate(28deg) scaleX(1.18) scaleY(0.58);
  }
  to {
    transform: rotate(388deg) scaleX(1.18) scaleY(0.58);
  }
}

@keyframes orbit-spin-b {
  from {
    transform: rotate(-28deg) scaleX(1.18) scaleY(0.58);
  }
  to {
    transform: rotate(-388deg) scaleX(1.18) scaleY(0.58);
  }
}

@keyframes core-pulse {
  0%,
  100% {
    transform: translate(-50%, -50%) scale(1);
    box-shadow: 0 0 18px rgba(134, 231, 255, 0.45);
  }
  50% {
    transform: translate(-50%, -50%) scale(1.18);
    box-shadow: 0 0 24px rgba(255, 209, 111, 0.55);
  }
}

.nav-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.7rem 1rem;
  border-radius: 999px;
  color: var(--muted);
  text-decoration: none;
  font-weight: 700;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(150, 201, 255, 0.1);
  transition: transform 180ms ease, color 180ms ease, background-color 180ms ease;
}

.nav-link:hover {
  transform: translateY(-1px);
  color: var(--text);
}

.nav-link.is-active {
  color: #032335;
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  border-color: transparent;
}

.hero {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1rem;
  align-items: stretch;
}

.hero-copy,
.hero-card,
.info-card,
.feature-card,
.footer-note {
  border: 1px solid var(--line);
  background: var(--panel);
  backdrop-filter: blur(14px);
  box-shadow: var(--shadow);
  border-radius: 26px;
}

.hero-copy {
  padding: 2rem;
}

.eyebrow,
.label {
  margin: 0;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent);
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  margin: 0.45rem 0 1rem;
  font-size: clamp(2.8rem, 6vw, 5rem);
  line-height: 0.95;
  max-width: 8ch;
}

.lead {
  margin-bottom: 0;
  max-width: 60ch;
  color: var(--muted);
  line-height: 1.75;
  font-size: 1.04rem;
}

.hero-tags {
  display: flex;
  gap: 0.7rem;
  margin-top: 1.4rem;
  flex-wrap: wrap;
}

.hero-tags span {
  display: inline-flex;
  align-items: center;
  padding: 0.55rem 0.9rem;
  border-radius: 999px;
  color: var(--text);
  font-size: 0.86rem;
  font-weight: 700;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(150, 201, 255, 0.12);
}

.primary,
.secondary,
.card-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 999px;
  padding: 0.85rem 1.2rem;
  font-weight: 700;
  text-decoration: none;
  transition: transform 180ms ease, box-shadow 180ms ease, background-color 180ms ease;
}

.primary {
  color: #032335;
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  box-shadow: 0 12px 32px rgba(37, 191, 255, 0.28);
}

.secondary {
  color: var(--text);
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(150, 201, 255, 0.14);
}

.card-link {
  margin-top: 1rem;
  color: #032335;
  background: linear-gradient(135deg, #ffd98e, var(--energy));
  width: fit-content;
}

.primary:hover,
.secondary:hover,
.card-link:hover {
  transform: translateY(-2px);
}

.hero-card {
  padding: 1rem;
  display: grid;
  gap: 0.8rem;
}

.hero-card article {
  padding: 1rem;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(150, 201, 255, 0.08);
}

.value {
  margin: 0.28rem 0 0;
  font-size: 1.2rem;
  font-weight: 800;
}

.overview-grid,
.cards-grid {
  display: grid;
  gap: 1rem;
  margin-top: 1rem;
}

.overview-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.cards-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.info-card,
.feature-card {
  padding: 1.35rem;
}

.info-card h2,
.feature-card h3 {
  margin: 0.45rem 0 0.6rem;
}

.feature-card {
  position: relative;
  display: flex;
  flex-direction: column;
  min-height: 260px;
  overflow: hidden;
}

.feature-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--accent), var(--energy));
  opacity: 0.95;
}

.feature-card[data-topic="structure"]::before {
  background: linear-gradient(90deg, #7ce8ff, #9fffd5);
}

.feature-card[data-topic="half-life"]::before {
  background: linear-gradient(90deg, #ffd16f, #ff9d7a);
}

.feature-card[data-topic="fission"]::before {
  background: linear-gradient(90deg, #7ce8ff, #ffd16f);
}

.feature-card[data-topic="chain"]::before {
  background: linear-gradient(90deg, #7ef0ff, #86b8ff);
}

.feature-card[data-topic="radiation"]::before {
  background: linear-gradient(90deg, #ffe08a, #ffad95);
}

.feature-card[data-topic="changes"]::before {
  background: linear-gradient(90deg, #9fffd5, #7ce8ff);
}

.info-card p:last-child,
.feature-card p:last-of-type,
.footer-note p {
  margin-bottom: 0;
  color: var(--muted);
  line-height: 1.65;
}

.topic-meta {
  margin-top: auto;
  margin-bottom: 0;
  color: var(--accent);
  font-size: 0.86rem;
  font-weight: 700;
}

.footer-note {
  margin-top: 1rem;
  padding: 1rem 1.2rem;
}

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

  .overview-grid,
  .cards-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .page {
    width: min(100vw - 1rem, 100%);
    padding-top: 0.8rem;
  }

  .overview-grid,
  .cards-grid {
    grid-template-columns: 1fr;
  }

  .hero-copy,
  .hero-card,
  .info-card,
  .feature-card,
  .footer-note {
    border-radius: 20px;
  }

  .hero-copy,
  .info-card,
  .feature-card {
    padding: 1rem;
  }

  .primary,
  .secondary,
  .card-link,
  .nav-link {
    width: 100%;
  }

  .nav-brand {
    width: 100%;
    justify-content: center;
    margin-right: 0;
    padding-bottom: 0.55rem;
  }
}