/**
 * 生物学讲解页共用外壳。
 * 画布、标题、内容面板与中心法则的步骤条都从这里来，
 * 各页只保留自己的图示和交互。
 */
body.bio-page,
body.biology-page {
    font-family: var(--bx-font-body);
    color: var(--bx-ink);
    background-color: var(--bx-canvas);
    background-image: var(--bx-gradient-mesh);
    min-height: 100vh;
    padding: 28px 20px 72px;
}

body.bio-page .container,
body.biology-page .container {
    margin-left: auto;
    margin-right: auto;
    background: transparent;
    border-radius: 0;
    box-shadow: none;
    overflow: visible;
}

body.bio-page .header,
body.biology-page .header {
    background: transparent !important;
    color: var(--bx-ink) !important;
    text-align: left !important;
    text-shadow: none !important;
    padding: 8px 0 28px !important;
}

body.bio-page .header h1,
body.biology-page .header h1 {
    font-family: var(--bx-font-display);
    font-size: clamp(36px, 4.6vw, 56px) !important;
    font-weight: 750;
    letter-spacing: -0.045em;
    line-height: 1.08;
    color: var(--bx-ink) !important;
    text-shadow: none !important;
    margin-bottom: 12px;
}

body.bio-page .header p,
body.bio-page .header .sub,
body.biology-page .header p,
body.biology-page .header .lead,
body.biology-page .header .quote {
    color: var(--bx-muted) !important;
    opacity: 1 !important;
    max-width: 40em;
    margin-left: 0 !important;
    margin-right: 0 !important;
    font-size: 18px !important;
    line-height: 1.65;
    text-shadow: none !important;
}

body.biology-page .header .quote {
    font-size: 15px !important;
    border-top: 1px solid var(--bx-line);
    padding-top: 14px;
}

body.bio-page .header a,
body.biology-page .header a,
body.bio-page .back-link,
body.biology-page .back-link,
body.bio-page .content a,
body.biology-page .content a {
    color: var(--bx-primary);
}

body.bio-page .content,
body.biology-page .content {
    background: var(--bx-surface);
    border: 1px solid var(--bx-line);
    border-radius: var(--bx-radius-lg);
    box-shadow: var(--bx-shadow-card);
}

body.bio-page .step-btn,
body.biology-page .step-btn {
    border-color: var(--bx-primary);
    color: var(--bx-primary);
    background: var(--bx-surface);
}

body.bio-page .step-btn.active,
body.biology-page .step-btn.active,
body.bio-page .tab-btn.active,
body.biology-page .tab-btn.active,
body.bio-page .nav-btns button,
body.biology-page .nav-btns button {
    background: var(--bx-primary);
    color: #fff;
    border-color: var(--bx-primary);
}

body.bio-page .step-btn.done,
body.biology-page .step-btn.done {
    background: var(--bx-secondary-soft);
    border-color: rgba(31, 168, 154, 0.45);
    color: #14756c;
}

body.bio-page .step-desc,
body.biology-page .step-desc {
    background: var(--bx-canvas);
    border-left-color: var(--bx-accent);
    color: var(--bx-ink);
}

body.bio-page:has(.sheet) #demo-nav-mount,
.sheet {
    max-width: 1080px;
    margin-left: auto;
    margin-right: auto;
}

.sheet .mast {
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(260px, 0.85fr);
    gap: 36px;
    align-items: end;
    padding: 12px 0 36px;
}

.sheet .kicker {
    margin: 0 0 12px;
    font-family: var(--bx-font-mono);
    font-size: 12px;
    letter-spacing: 0.12em;
    color: var(--bx-primary);
}

.sheet .mast h1 {
    margin: 0;
    font-family: var(--bx-font-display);
    font-size: clamp(40px, 5vw, 64px);
    font-weight: 750;
    letter-spacing: -0.045em;
    line-height: 1.05;
    color: var(--bx-ink);
}

.sheet .lede {
    margin: 16px 0 0;
    max-width: 36em;
    font-size: 18px;
    line-height: 1.65;
    color: var(--bx-muted);
}

.sheet .figure {
    margin: 0;
    padding: 16px 18px 14px;
    background: var(--bx-surface);
    border: 1px solid var(--bx-line);
    border-radius: var(--bx-radius-md);
}

.sheet .figure svg { display: block; width: 100%; height: auto; }

.sheet .figure figcaption {
    margin-top: 8px;
    font-family: var(--bx-font-mono);
    font-size: 12px;
    color: var(--bx-muted);
}

.sheet .strand { fill: none; stroke-width: 2.5; stroke-linecap: round; }
.sheet .strand-dna { stroke: var(--bx-primary); }
.sheet .strand-rna { stroke: var(--bx-secondary); }
.sheet .rung { stroke: var(--bx-primary); stroke-opacity: 0.35; stroke-width: 1.5; }
.sheet .tick { stroke: var(--bx-secondary); stroke-opacity: 0.7; stroke-width: 1.5; }
.sheet .backbone { fill: none; stroke: var(--bx-accent); stroke-opacity: 0.45; stroke-width: 1.5; }
.sheet .bead { fill: var(--bx-accent); }
.sheet .arrow { fill: none; stroke: var(--bx-muted); stroke-width: 1.25; }
.sheet .fig-label {
    font-family: var(--bx-font-mono);
    font-size: 11px;
    fill: var(--bx-muted);
}

.sheet .stage-layout {
    display: grid;
    grid-template-columns: 272px minmax(0, 1fr);
    gap: 28px;
    align-items: start;
}

.sheet .flow {
    list-style: none;
    margin: 0;
    padding: 4px 0;
    display: flex;
    flex-direction: column;
    gap: 6px;
    position: relative;
}

.sheet .flow::before {
    content: "";
    position: absolute;
    left: 22px;
    top: 28px;
    bottom: 28px;
    width: 1px;
    background: var(--bx-line);
}

.sheet .flow-node {
    position: relative;
    display: grid;
    grid-template-columns: 36px 1fr;
    gap: 8px;
    align-items: center;
    width: 100%;
    padding: 12px 12px 12px 8px;
    text-align: left;
    font: inherit;
    color: inherit;
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--bx-radius-md);
    cursor: pointer;
}

.sheet .flow-node:hover { background: rgba(255, 255, 255, 0.72); }
.sheet .flow-node:active { transform: translateY(1px); }
.sheet .flow-node:focus-visible {
    outline: 2px solid var(--bx-primary);
    outline-offset: 2px;
}
.sheet .flow-node.active {
    background: var(--bx-surface);
    border-color: var(--bx-line);
    box-shadow: inset 3px 0 0 var(--bx-accent);
}
.sheet .idx {
    font-family: var(--bx-font-mono);
    font-size: 12px;
    color: var(--bx-muted);
    text-align: center;
}
.sheet .flow-node.active .idx { color: var(--bx-accent); }
.sheet .flow-node h3 {
    margin: 0;
    font-size: 16px;
    font-weight: 650;
    letter-spacing: -0.02em;
}
.sheet .flow-node p { margin: 2px 0 0; font-size: 13px; color: var(--bx-muted); }

.sheet .detail-panel {
    background: var(--bx-surface);
    border: 1px solid var(--bx-line);
    border-radius: var(--bx-radius-lg);
    padding: 28px 28px 24px;
    min-height: 240px;
    box-shadow: var(--bx-shadow-card);
}
.sheet .detail-panel h3 {
    margin: 0 0 12px;
    font-size: 22px;
    letter-spacing: -0.03em;
    font-weight: 650;
}
.sheet .detail-panel p {
    margin: 0;
    max-width: 62ch;
    line-height: 1.7;
    color: var(--bx-ink);
}
.sheet .detail-panel a { color: var(--bx-primary); }

.sheet .seq-display {
    margin: 16px 0;
    padding: 16px 18px;
    font-family: var(--bx-font-mono);
    font-size: 15px;
    letter-spacing: 0.12em;
    line-height: 1.9;
    background: var(--bx-canvas);
    border-radius: var(--bx-radius-md);
    word-break: break-all;
}
.sheet .seq-display .highlight {
    background: var(--bx-accent-soft);
    border-radius: 4px;
    padding: 1px 4px;
}
.sheet .base { font-style: normal; font-weight: 700; }
.sheet .base-A { color: var(--bx-primary); }
.sheet .base-T, .sheet .base-U { color: #14756c; }
.sheet .base-G { color: #8a5a2b; }
.sheet .base-C { color: #c4544a; }

.sheet .codon-table { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.sheet .codon {
    display: inline-flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 2px;
    padding: 8px 12px;
    font: inherit;
    font-family: var(--bx-font-mono);
    font-size: 13px;
    letter-spacing: 0.04em;
    color: var(--bx-ink);
    background: var(--bx-surface);
    border: 1px solid var(--bx-line);
    border-radius: 8px;
    cursor: pointer;
}
.sheet .codon .aa {
    font-family: var(--bx-font-body);
    font-size: 12px;
    letter-spacing: 0;
    color: var(--bx-muted);
}
.sheet .codon:hover { border-color: var(--bx-primary); }
.sheet .codon:focus-visible { outline: 2px solid var(--bx-primary); outline-offset: 2px; }
.sheet .codon.active {
    border-color: var(--bx-primary);
    background: var(--bx-primary-soft);
}
.sheet .codon.active .aa { color: var(--bx-primary); }
.sheet .peptide { margin-top: 14px; font-weight: 650; color: var(--bx-primary); }

.sheet .further {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 18px;
    align-items: baseline;
    margin-top: 36px;
    padding-top: 18px;
    border-top: 1px solid var(--bx-line);
    font-size: 15px;
}
.sheet .further span { color: var(--bx-muted); font-size: 13px; }
.sheet .further a { color: var(--bx-primary); text-underline-offset: 3px; }

@media (max-width: 800px) {
    .sheet .mast,
    .sheet .stage-layout { grid-template-columns: 1fr; gap: 20px; }
    .sheet .detail-panel { padding: 20px 16px; }
    .sheet .flow { flex-direction: row; overflow-x: auto; padding-bottom: 4px; }
    .sheet .flow::before { display: none; }
    .sheet .flow-node { min-width: 168px; }
    body.bio-page .content,
    body.biology-page .content { padding: 20px 16px; }
}

@media (prefers-reduced-motion: reduce) {
    .sheet .flow-node:active { transform: none; }
}