:root {
  --bg: #0f1419;
  --bg-card: #1a2332;
  --bg-card-2: #1f2b3d;
  --border: #2d3e54;
  --accent: #4fc3f7;
  --accent-2: #ffb74d;
  --accent-3: #81c784;
  --accent-4: #f06292;
  --text: #e3eaf2;
  --text-dim: #9fb1c5;
  --code-bg: #0a0e14;
  --formula-bg: #142233;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  padding: 0;
}
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 40px 24px 80px;
}
header {
  text-align: center;
  padding: 50px 20px 30px;
  background: linear-gradient(135deg, #1a2a40 0%, #0f1419 100%);
  border-bottom: 2px solid var(--accent);
  margin-bottom: 30px;
}
header h1 {
  font-size: 2.2em;
  margin: 0 0 10px;
  color: var(--accent);
  letter-spacing: 0.5px;
}
header .subtitle {
  font-size: 1.1em;
  color: var(--text-dim);
  max-width: 800px;
  margin: 0 auto;
}
header .stage-badge {
  display: inline-block;
  background: var(--accent);
  color: #0a0e14;
  padding: 6px 16px;
  border-radius: 20px;
  font-size: 0.85em;
  font-weight: 700;
  margin-bottom: 14px;
  letter-spacing: 1px;
  text-transform: uppercase;
}
h2 {
  color: var(--accent);
  border-bottom: 2px solid var(--border);
  padding-bottom: 8px;
  margin-top: 40px;
  font-size: 1.5em;
}
h3 {
  color: var(--accent-2);
  margin-top: 28px;
  font-size: 1.2em;
}
h4 {
  color: var(--accent-3);
  margin: 18px 0 8px;
  font-size: 1.05em;
}
.stage {
  background: var(--bg-card);
  border-radius: 8px;
  padding: 24px 28px;
  margin: 20px 0;
  box-shadow: 0 4px 12px rgba(0,0,0,0.25);
}
.stage h2:first-child { margin-top: 0; }
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
  margin: 20px 0;
}
.box {
  background: var(--bg-card-2);
  border-radius: 6px;
  padding: 14px 18px;
  border-left: 3px solid var(--accent-2);
}
.box.in { border-left-color: var(--accent-3); }
.box.out { border-left-color: var(--accent-4); }
.box.actors { border-left-color: var(--accent-2); }
.box.enzymes { border-left-color: var(--accent); }
.box-label {
  font-size: 0.75em;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--text-dim);
  font-weight: 700;
  margin-bottom: 8px;
}
ul, ol { padding-left: 22px; margin: 8px 0; }
li { margin: 4px 0; }
.formula {
  background: var(--formula-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 14px 18px;
  margin: 14px 0;
  font-family: "JetBrains Mono", "Cascadia Code", Consolas, monospace;
  font-size: 0.98em;
  overflow-x: auto;
  color: #c8e6f5;
  white-space: nowrap;
}
.formula .label {
  display: block;
  font-family: -apple-system, sans-serif;
  color: var(--accent-2);
  font-size: 0.85em;
  margin-bottom: 6px;
  white-space: normal;
  text-transform: uppercase;
  letter-spacing: 1px;
}
.formula-block {
  background: var(--formula-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 14px 18px;
  margin: 14px 0;
  font-family: "JetBrains Mono", Consolas, monospace;
  font-size: 0.95em;
  overflow-x: auto;
  color: #c8e6f5;
  white-space: pre;
  line-height: 1.5;
}
table {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0;
  background: var(--bg-card-2);
  border-radius: 6px;
  overflow: hidden;
}
th, td {
  text-align: left;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border);
  font-size: 0.93em;
}
th {
  background: #15202e;
  color: var(--accent);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-size: 0.78em;
}
tr:last-child td { border-bottom: none; }
tr:hover { background: rgba(79, 195, 247, 0.05); }
.toc {
  background: var(--bg-card);
  border-radius: 8px;
  padding: 24px 28px;
  margin: 0 0 30px;
  border: 1px solid var(--border);
}
.toc h2 {
  margin-top: 0;
  border-bottom: 1px solid var(--border);
}
.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 12px;
  margin-top: 20px;
}
.toc-card {
  background: var(--bg-card-2);
  border-left: 3px solid var(--accent);
  border-radius: 6px;
  padding: 14px 18px;
  text-decoration: none;
  color: var(--text);
  transition: transform 0.15s, border-color 0.15s, background 0.15s;
  display: block;
}
.toc-card:hover {
  transform: translateX(3px);
  background: #243349;
  border-left-color: var(--accent-2);
}
.toc-card .num {
  display: inline-block;
  background: var(--accent);
  color: #0a0e14;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.75em;
  font-weight: 700;
  margin-bottom: 6px;
}
.toc-card .title {
  font-weight: 600;
  font-size: 1.02em;
  color: var(--text);
}
.toc-card .desc {
  font-size: 0.85em;
  color: var(--text-dim);
  margin-top: 4px;
}
.chem-sub { font-size: 0.78em; vertical-align: -0.25em; }
.chem-sup { font-size: 0.78em; vertical-align: 0.5em; }
.arrow { color: var(--accent-2); font-weight: bold; }
.note {
  background: rgba(255, 183, 77, 0.08);
  border-left: 3px solid var(--accent-2);
  padding: 10px 16px;
  margin: 14px 0;
  border-radius: 4px;
  font-size: 0.93em;
  color: var(--text-dim);
}
.process {
  background: linear-gradient(135deg, #182838 0%, #15202e 100%);
  border-left: 4px solid var(--accent-3);
  border-radius: 6px;
  padding: 18px 24px;
  margin: 20px 0;
  line-height: 1.75;
}
.process h4 {
  color: var(--accent-3);
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 1.1em;
  text-transform: uppercase;
  letter-spacing: 1px;
}
.process p {
  margin: 10px 0;
  color: #d8e3ef;
}
.process p:first-of-type { margin-top: 0; }
.process p:last-child { margin-bottom: 0; }
.process .step {
  counter-increment: step-counter;
  padding: 8px 0 8px 38px;
  position: relative;
  border-bottom: 1px dashed rgba(255,255,255,0.06);
}
.process .step:last-child { border-bottom: none; }
.process .step::before {
  content: counter(step-counter);
  position: absolute;
  left: 0;
  top: 8px;
  width: 26px;
  height: 26px;
  background: var(--accent-3);
  color: #0a0e14;
  border-radius: 50%;
  text-align: center;
  line-height: 26px;
  font-weight: 700;
  font-size: 0.85em;
}
.process.numbered { counter-reset: step-counter; }
.highlight {
  color: var(--accent-2);
  font-weight: 600;
}
.summary-final {
  background: linear-gradient(135deg, #1a3a5c 0%, #0f2540 100%);
  border: 2px solid var(--accent);
  border-radius: 10px;
  padding: 30px;
  margin: 50px 0 30px;
  text-align: center;
}
.summary-final .formula-block {
  background: rgba(0,0,0,0.3);
  text-align: center;
  font-size: 1.15em;
}
footer {
  text-align: center;
  color: var(--text-dim);
  padding: 30px 20px;
  font-size: 0.85em;
  border-top: 1px solid var(--border);
  margin-top: 60px;
}

/* Page navigation between stages */
.page-nav {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: 12px;
  margin: 40px 0 20px;
  flex-wrap: wrap;
}
.page-nav a {
  flex: 1 1 30%;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 18px;
  text-decoration: none;
  color: var(--text);
  transition: all 0.15s;
  display: flex;
  flex-direction: column;
  min-width: 200px;
}
.page-nav a:hover {
  border-color: var(--accent);
  background: #243349;
}
.page-nav a.prev { text-align: left; }
.page-nav a.home { text-align: center; flex: 0 1 auto; min-width: 130px; }
.page-nav a.next { text-align: right; align-items: flex-end; }
.page-nav .nav-label {
  font-size: 0.75em;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 1.2px;
  margin-bottom: 4px;
}
.page-nav .nav-title {
  font-weight: 600;
  color: var(--accent);
  font-size: 1em;
}
.page-nav a.disabled {
  opacity: 0.4;
  pointer-events: none;
}

.breadcrumbs {
  font-size: 0.9em;
  color: var(--text-dim);
  margin-bottom: 18px;
}
.breadcrumbs a {
  color: var(--accent);
  text-decoration: none;
}
.breadcrumbs a:hover { text-decoration: underline; }
.breadcrumbs .sep { margin: 0 8px; color: var(--border); }

@media (max-width: 768px) {
  .container {
    padding: 16px 10px 40px;
  }
  header {
    padding: 28px 12px 20px;
    margin-bottom: 16px;
  }
  header h1 {
    font-size: 1.5em;
    line-height: 1.2;
    margin: 0 0 6px;
  }
  header .subtitle {
    font-size: 0.95em;
    line-height: 1.45;
  }
  header .stage-badge {
    font-size: 0.72em;
    padding: 4px 10px;
    margin-bottom: 10px;
  }
  h2 { font-size: 1.25em; margin-top: 24px; }
  h3 { font-size: 1.08em; margin-top: 18px; }
  h4 { font-size: 0.98em; margin: 12px 0 6px; }

  .stage {
    padding: 14px 12px;
    margin: 14px 0;
    border-radius: 6px;
  }
  .process {
    padding: 12px 12px;
    margin: 14px 0;
    border-left-width: 3px;
    line-height: 1.55;
  }
  .process h4 {
    font-size: 0.95em;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
  }
  .process .step {
    padding: 6px 0 6px 30px;
    font-size: 0.92em;
  }
  .process .step::before {
    width: 22px;
    height: 22px;
    line-height: 22px;
    font-size: 0.78em;
    top: 6px;
  }
  .process p { margin: 6px 0; font-size: 0.92em; }

  .grid {
    grid-template-columns: 1fr;
    gap: 10px;
    margin: 14px 0;
  }
  .box {
    padding: 10px 12px;
    border-left-width: 2px;
  }
  .box-label {
    font-size: 0.7em;
    letter-spacing: 1px;
    margin-bottom: 4px;
  }
  .box ul, .box ol { padding-left: 18px; }
  .box li { font-size: 0.9em; }

  ul, ol { padding-left: 18px; }

  .formula {
    padding: 10px 12px;
    margin: 10px 0;
    font-size: 0.85em;
    border-radius: 4px;
  }
  .formula .label {
    font-size: 0.75em;
    letter-spacing: 0.5px;
    margin-bottom: 4px;
  }
  .formula-block {
    padding: 10px 12px;
    margin: 10px 0;
    font-size: 0.78em;
    line-height: 1.4;
    border-radius: 4px;
  }

  table { font-size: 0.85em; margin: 12px 0; }
  th, td { padding: 6px 8px; font-size: 0.88em; }
  th { font-size: 0.7em; letter-spacing: 0.3px; }

  .toc {
    padding: 14px 12px;
    margin: 0 0 16px;
  }
  .toc-grid {
    grid-template-columns: 1fr;
    gap: 8px;
    margin-top: 14px;
  }
  .toc-card {
    padding: 10px 12px;
    border-left-width: 2px;
  }
  .toc-card .num {
    font-size: 0.7em;
    padding: 2px 6px;
  }
  .toc-card .title { font-size: 0.95em; }
  .toc-card .desc { font-size: 0.8em; margin-top: 2px; }

  .note {
    padding: 8px 12px;
    margin: 10px 0;
    font-size: 0.88em;
  }

  .summary-final {
    padding: 16px 12px;
    margin: 24px 0 16px;
    border-radius: 6px;
    border-width: 1px;
  }
  .summary-final h2 { font-size: 1.15em; }
  .summary-final .formula-block { font-size: 0.78em; }

  .breadcrumbs {
    font-size: 0.85em;
    margin-bottom: 12px;
  }

  .page-nav {
    flex-direction: column;
    gap: 8px;
    margin: 24px 0 12px;
  }
  .page-nav a {
    flex: 1 1 100%;
    padding: 10px 14px;
    border-radius: 6px;
    text-align: left !important;
    align-items: flex-start !important;
  }
  .page-nav a.next, .page-nav a.home {
    text-align: left !important;
    align-items: flex-start !important;
  }
  .page-nav .nav-label {
    font-size: 0.7em;
    letter-spacing: 0.8px;
    margin-bottom: 2px;
  }
  .page-nav .nav-title { font-size: 0.92em; }

  footer {
    padding: 18px 12px;
    margin-top: 30px;
    font-size: 0.8em;
  }
}

@media (max-width: 380px) {
  .container { padding: 12px 8px 30px; }
  header h1 { font-size: 1.3em; }
  header .subtitle { font-size: 0.88em; }
  .stage { padding: 12px 10px; }
  .process { padding: 10px 10px; }
  .process .step { padding: 6px 0 6px 28px; font-size: 0.88em; }
  .formula, .formula-block { font-size: 0.75em; padding: 8px 10px; }
  .box { padding: 8px 10px; }
  .toc-card .title { font-size: 0.9em; }
}