/* ============================================================
   carbon.css — Styles for the Carbon knowledge page
   ============================================================ */

/* ── Hero ── */
.carbon-hero {
  position: relative;
  min-height: 70vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: var(--nav-h);
  overflow: hidden;
  text-align: center;
  border-bottom: 1px solid var(--border);
}

.carbon-hero__bg {
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 70% 60% at 50% 50%, rgba(201,168,76,0.05) 0%, transparent 70%);
}

.carbon-hero__svg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.carbon-hero__content {
  position: relative;
  z-index: 2;
  padding: 5rem 2rem;
}

.carbon-hero__title {
  font-family: var(--font-serif);
  font-size: clamp(4rem, 12vw, 9rem);
  font-weight: 400;
  line-height: 1;
  color: var(--white);
  letter-spacing: -0.02em;
  margin-bottom: 1.5rem;
}
.carbon-hero__title em {
  color: var(--gold);
  font-style: italic;
}

.carbon-hero__sub {
  font-size: 1.125rem;
  color: var(--mid);
  line-height: 1.7;
  margin-bottom: 3rem;
}

/* Chapter nav */
.carbon-chapnav {
  display: flex;
  gap: 0;
  justify-content: center;
  flex-wrap: wrap;
  border: 1px solid var(--border);
  display: inline-flex;
}

.carbon-chapnav a {
  padding: 0.6rem 1.25rem;
  font-size: 0.6875rem;
  font-weight: 400;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--muted);
  border-right: 1px solid var(--border);
  transition: color 0.2s, background 0.2s;
}
.carbon-chapnav a:last-child { border-right: none; }
.carbon-chapnav a:hover {
  color: var(--gold);
  background: rgba(201,168,76,0.05);
}

/* ── Section scroll offset for sticky nav ── */
.carbon-section {
  scroll-margin-top: calc(var(--nav-h) + 2rem);
}

/* ── Atom Diagram ── */
.carbon-diagram {
  margin: 3rem 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.carbon-diagram__label {
  font-size: 0.6875rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
}

.atom-diagram {
  position: relative;
  width: 260px;
  height: 260px;
}

.atom-nucleus {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 64px; height: 64px;
  border-radius: 50%;
  background: var(--dark-2);
  border: 2px solid var(--gold);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 3;
  box-shadow: 0 0 20px rgba(201,168,76,0.2);
}

.atom-nucleus__symbol {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  color: var(--gold);
  line-height: 1;
}

.atom-nucleus__num {
  font-size: 0.5rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}

.atom-shell {
  position: absolute;
  top: 50%; left: 50%;
  border-radius: 50%;
  border: 1px solid var(--border);
  transform: translate(-50%, -50%);
}

.atom-shell--1 {
  width: 120px; height: 120px;
  animation: spinShell 6s linear infinite;
}

.atom-shell--2 {
  width: 220px; height: 220px;
  animation: spinShell 10s linear infinite reverse;
}

@keyframes spinShell {
  from { transform: translate(-50%, -50%) rotate(0deg); }
  to   { transform: translate(-50%, -50%) rotate(360deg); }
}

.atom-electron {
  position: absolute;
  width: 10px; height: 10px;
  border-radius: 50%;
  background: var(--mid);
  top: 50%; left: 50%;
  transform:
    translate(-50%, -50%)
    rotate(var(--angle))
    translateX(55px)
    rotate(calc(-1 * var(--angle)));
}

.atom-electron--outer {
  background: var(--gold);
  width: 10px; height: 10px;
  transform:
    translate(-50%, -50%)
    rotate(var(--angle))
    translateX(105px)
    rotate(calc(-1 * var(--angle)));
  box-shadow: 0 0 6px rgba(201,168,76,0.6);
}

.atom-shell-label {
  position: absolute;
  font-size: 0.5625rem;
  color: var(--muted);
  letter-spacing: 0.08em;
  white-space: nowrap;
}

.atom-shell-label--1 {
  top: 50%;
  left: calc(50% + 65px);
  transform: translateY(-50%);
}

.atom-shell-label--2 {
  top: 50%;
  left: calc(50% + 115px);
  transform: translateY(-50%);
}

/* ── Fact Row ── */
.carbon-fact-row {
  display: flex;
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2.5rem 0;
}

.carbon-fact {
  flex: 1;
  background: var(--dark);
  padding: 1.5rem 1rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.carbon-fact__val {
  font-family: var(--font-serif);
  font-size: 2rem;
  color: var(--gold);
  line-height: 1;
}

.carbon-fact__key {
  font-size: 0.625rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}

/* ── Bond Types ── */
.bond-types {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2.5rem 0;
}

.bond-type {
  background: var(--dark);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  transition: background 0.2s;
}
.bond-type:hover { background: var(--dark-2); }

.bond-type__diagram {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  height: 60px;
  margin-bottom: 0.5rem;
}

.bond-type__diagram--ring {
  height: 80px;
}
.bond-type__diagram--ring svg {
  width: 80px;
  height: 80px;
}

.bond-atom {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--dark-3);
  border: 1px solid var(--gold-dim);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-serif);
  font-size: 1rem;
  color: var(--gold);
}

.bond-line {
  background: var(--gold);
  height: 2px;
  width: 30px;
  position: relative;
}

.bond-line--double::before {
  content: '';
  position: absolute;
  top: -4px; left: 0; right: 0;
  height: 2px;
  background: var(--gold);
}

.bond-line--triple::before,
.bond-line--triple::after {
  content: '';
  position: absolute;
  left: 0; right: 0;
  height: 2px;
  background: var(--gold);
}
.bond-line--triple::before { top: -5px; }
.bond-line--triple::after  { top: 5px; }

.bond-type h3 {
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  font-weight: 400;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--white);
}

.bond-type p {
  font-size: 0.875rem;
  color: var(--muted);
  line-height: 1.65;
  margin: 0;
}

.bond-type__notation {
  font-family: var(--font-serif);
  font-size: 1.125rem;
  color: var(--gold);
  letter-spacing: 0.1em;
  margin-top: auto;
}

/* ── Allotropes Grid ── */
.allotropes-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2.5rem 0;
}

.allotrope-card {
  background: var(--dark);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  transition: background 0.25s;
}
.allotrope-card:hover { background: var(--dark-2); }

.allotrope-card--featured {
  background: var(--dark-2);
  border: 1px solid var(--gold-dim);
  margin: -1px;
  z-index: 1;
}

.allotrope-card__diagram {
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.allotrope-card__diagram svg {
  width: 120px;
  height: 100px;
}

.allotrope-card h3 {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  color: var(--white);
  font-weight: 400;
}

.allotrope-card__tag {
  font-size: 0.5625rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--gold);
  border: 1px solid var(--gold-dim);
  padding: 0.15rem 0.5rem;
  align-self: flex-start;
}

.allotrope-card p {
  font-size: 0.875rem;
  color: var(--muted);
  line-height: 1.65;
  margin: 0;
}

/* ── Life Molecules ── */
.life-molecules {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2.5rem 0;
}

.life-molecule {
  background: var(--dark);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  transition: background 0.2s;
}
.life-molecule:hover { background: var(--dark-2); }

.life-molecule h3 {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  color: var(--white);
  font-weight: 400;
}

.life-molecule p {
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.7;
  margin: 0;
  flex: 1;
}

.life-molecule__formula {
  font-family: var(--font-serif);
  font-size: 0.875rem;
  color: var(--gold);
  font-style: italic;
  margin-top: auto;
  padding-top: 0.75rem;
  border-top: 1px solid var(--border);
}

/* ── Carbon Cycle ── */
.cycle-diagram {
  display: flex;
  align-items: flex-start;
  gap: 0;
  margin: 2.5rem 0;
  overflow-x: auto;
  padding-bottom: 1rem;
}

.cycle-step {
  flex: 1;
  min-width: 120px;
  background: var(--dark);
  border: 1px solid var(--border);
  padding: 1.5rem 1rem;
  text-align: center;
}

.cycle-step__num {
  display: block;
  font-family: var(--font-serif);
  font-size: 1.5rem;
  color: var(--gold);
  margin-bottom: 0.5rem;
  line-height: 1;
}

.cycle-step h4 {
  font-family: var(--font-sans);
  font-size: 0.6875rem;
  font-weight: 400;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--white);
  margin-bottom: 0.75rem;
}

.cycle-step p {
  font-size: 0.8125rem;
  color: var(--muted);
  line-height: 1.6;
  margin: 0;
}

.cycle-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--gold-dim);
  font-size: 1.25rem;
  padding: 0 0.25rem;
  flex-shrink: 0;
  padding-top: 2rem;
}

.cycle-arrow--loop {
  font-size: 1.75rem;
  color: var(--gold);
}

/* ── Carbon Final Grid ── */
.carbon-final-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2.5rem 0;
}

.carbon-final-item {
  background: var(--dark);
  padding: 2rem 1rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.carbon-final-icon {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  color: var(--gold);
  line-height: 1;
}

.carbon-final-item p {
  font-size: 0.75rem;
  color: var(--muted);
  line-height: 1.5;
  margin: 0;
  letter-spacing: 0.03em;
}

/* ── Responsive ── */
@media (max-width: 900px) {
  .allotropes-grid { grid-template-columns: repeat(2, 1fr); }
  .carbon-final-grid { grid-template-columns: repeat(2, 1fr); }
  .cycle-diagram { flex-wrap: wrap; }
  .cycle-step { min-width: 140px; }
  .cycle-arrow { display: none; }
}

@media (max-width: 640px) {
  .bond-types { grid-template-columns: 1fr; }
  .life-molecules { grid-template-columns: 1fr; }
  .allotropes-grid { grid-template-columns: 1fr; }
  .carbon-fact-row { flex-wrap: wrap; }
  .carbon-fact { min-width: 45%; }
  .carbon-chapnav { flex-wrap: wrap; }
  .carbon-chapnav a { border-bottom: 1px solid var(--border); }
}