:root {
  --bg: #f3efe5;
  --panel: #fffaf0;
  --ink: #1d2a38;
  --muted: #5d6b78;
  --accent: #bf5b04;
  --accent-soft: #f3c48b;
  --line: #d8c9ae;
  --alkali: #f5b971;
  --alkaline: #f0d77b;
  --nonmetal: #8bc6a2;
  --halogen: #7db8d6;
  --noble: #b99de0;
  --unknown: #d8d2c6;
  --card-shadow: 0 12px 35px rgba(34, 35, 38, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Georgia, "Times New Roman", serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(191, 91, 4, 0.15), transparent 28%),
    radial-gradient(circle at bottom right, rgba(125, 184, 214, 0.18), transparent 26%),
    linear-gradient(180deg, #f8f2e8, #eee6d5);
  min-height: 100vh;
}

.page {
  width: min(1380px, calc(100vw - 32px));
  margin: 0 auto;
  padding: 24px 0 32px;
}

.hero {
  background: rgba(255, 250, 240, 0.92);
  border: 1px solid rgba(216, 201, 174, 0.8);
  border-radius: 24px;
  padding: 28px;
  box-shadow: var(--card-shadow);
  margin-bottom: 20px;
}

.hero h1 {
  margin: 0 0 12px;
  font-size: clamp(2rem, 4vw, 3.5rem);
  line-height: 1.05;
  letter-spacing: 0.03em;
}

.hero p {
  margin: 0;
  max-width: 900px;
  font-size: 1.05rem;
  color: var(--muted);
  line-height: 1.6;
}

.grid {
  display: grid;
  grid-template-columns: minmax(0, 1.65fr) minmax(320px, 0.9fr);
  gap: 20px;
  align-items: start;
}

.panel {
  background: rgba(255, 250, 240, 0.94);
  border: 1px solid rgba(216, 201, 174, 0.85);
  border-radius: 24px;
  box-shadow: var(--card-shadow);
  overflow: hidden;
}

.panel-header {
  padding: 18px 22px 10px;
}

.panel-header h2,
.panel-header h3 {
  margin: 0 0 6px;
  font-size: 1.35rem;
}

.panel-header p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.table-wrap {
  padding: 8px 18px 24px;
  overflow-x: auto;
}

.periodic-table {
  display: grid;
  grid-template-columns: 64px repeat(18, minmax(62px, 1fr));
  gap: 8px;
  min-width: 1240px;
  align-items: stretch;
}

.corner,
.group-label,
.period-label {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  font-size: 0.88rem;
  min-height: 38px;
}

.group-label {
  font-weight: 700;
  letter-spacing: 0.04em;
}

.period-label {
  font-weight: 700;
}

.element {
  border: 1px solid rgba(29, 42, 56, 0.12);
  border-radius: 16px;
  min-height: 94px;
  padding: 10px 9px 8px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  cursor: pointer;
  transition: transform 180ms ease, box-shadow 180ms ease, border-color 180ms ease;
  position: relative;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
}

.element:hover,
.element:focus-visible {
  transform: translateY(-3px);
  box-shadow: 0 14px 24px rgba(0, 0, 0, 0.12);
  border-color: rgba(29, 42, 56, 0.35);
  outline: none;
}

.element.active {
  box-shadow: 0 0 0 3px rgba(191, 91, 4, 0.3), 0 16px 28px rgba(0, 0, 0, 0.16);
  border-color: rgba(191, 91, 4, 0.55);
}

.element-number {
  font-size: 0.75rem;
  color: rgba(29, 42, 56, 0.82);
}

.element-symbol {
  font-size: 1.72rem;
  font-weight: 700;
  line-height: 1;
  text-align: center;
  letter-spacing: 0.04em;
}

.element-meta {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  font-size: 0.72rem;
  color: rgba(29, 42, 56, 0.82);
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 0 22px 22px;
}

.legend-item {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  font-size: 0.92rem;
}

.legend-swatch {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 1px solid rgba(29, 42, 56, 0.15);
}

.details {
  padding-bottom: 18px;
  position: sticky;
  top: 16px;
}

.details-body {
  padding: 0 22px 8px;
}

.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 14px;
}

.tag {
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(191, 91, 4, 0.09);
  color: var(--ink);
  font-size: 0.84rem;
  border: 1px solid rgba(191, 91, 4, 0.18);
}

.facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-bottom: 20px;
}

.fact {
  border: 1px solid rgba(216, 201, 174, 0.9);
  background: rgba(255, 255, 255, 0.58);
  border-radius: 16px;
  padding: 12px;
}

.fact span {
  display: block;
  font-size: 0.8rem;
  color: var(--muted);
  margin-bottom: 4px;
}

.fact strong {
  font-size: 1.05rem;
}

.section-title {
  font-size: 1rem;
  margin: 18px 0 10px;
}

.explainer {
  color: var(--muted);
  line-height: 1.55;
  font-size: 0.95rem;
  margin: 0 0 14px;
}

.lewis-box {
  min-height: 220px;
  border: 1px solid rgba(216, 201, 174, 0.9);
  background:
    radial-gradient(circle at center, rgba(191, 91, 4, 0.07), transparent 52%),
    rgba(255, 255, 255, 0.62);
  border-radius: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 18px;
  padding: 12px;
}

.lewis-svg,
.bohr-svg {
  width: min(100%, 310px);
  height: auto;
  display: block;
}

.bohr-box {
  min-height: 340px;
  border: 1px solid rgba(216, 201, 174, 0.9);
  background:
    radial-gradient(circle at center, rgba(125, 184, 214, 0.08), transparent 58%),
    rgba(255, 255, 255, 0.62);
  border-radius: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 12px;
}

.note {
  margin: 14px 0 0;
  padding: 12px 14px;
  background: rgba(139, 198, 162, 0.14);
  border: 1px solid rgba(139, 198, 162, 0.28);
  border-radius: 14px;
  color: var(--ink);
  line-height: 1.55;
  font-size: 0.92rem;
}

.placeholder {
  padding: 16px;
  color: var(--muted);
  text-align: center;
  line-height: 1.6;
}

.footer {
  margin-top: 18px;
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 1040px) {
  .grid {
    grid-template-columns: 1fr;
  }

  .details {
    position: static;
  }
}

@media (max-width: 640px) {
  .page {
    width: min(100vw - 18px, 1380px);
    padding-top: 14px;
  }

  .hero,
  .panel {
    border-radius: 18px;
  }

  .hero {
    padding: 20px;
  }

  .panel-header,
  .details-body,
  .legend {
    padding-left: 16px;
    padding-right: 16px;
  }

  .facts {
    grid-template-columns: 1fr;
  }
}