:root {
        --bg: #f6f0e3;
        --bg-deep: #ece0ca;
        --paper: rgba(255, 251, 244, 0.84);
        --paper-strong: rgba(255, 251, 244, 0.94);
        --ink: #1b2830;
        --muted: #607180;
        --accent: #d16f2b;
        --accent-2: #0e7278;
        --accent-3: #b6421f;
        --line: rgba(27, 40, 48, 0.1);
        --shadow-soft: 0 18px 60px rgba(71, 49, 23, 0.13);
        --shadow-strong: 0 24px 74px rgba(34, 28, 20, 0.18);
        --radius-xl: 34px;
        --radius-lg: 24px;
        --radius-md: 18px;
      }

      * {
        box-sizing: border-box;
      }

      html {
        scroll-behavior: smooth;
      }

      body {
        margin: 0;
        font-family: "Manrope", sans-serif;
        color: var(--ink);
        background:
          radial-gradient(circle at 15% 10%, rgba(209, 111, 43, 0.18), transparent 24%),
          radial-gradient(circle at 82% 12%, rgba(14, 114, 120, 0.18), transparent 26%),
          linear-gradient(180deg, rgba(255, 255, 255, 0.44), transparent 22%),
          linear-gradient(180deg, var(--bg), var(--bg-deep));
        min-height: 100vh;
      }

      body::before {
        content: "";
        position: fixed;
        inset: 0;
        pointer-events: none;
        background-image:
          linear-gradient(rgba(27, 40, 48, 0.03) 1px, transparent 1px),
          linear-gradient(90deg, rgba(27, 40, 48, 0.03) 1px, transparent 1px);
        background-size: 40px 40px;
        mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.34), transparent 78%);
      }

      .page {
        width: min(1340px, calc(100vw - 28px));
        margin: 0 auto;
        padding: 20px 0 56px;
      }

      .hero {
        position: relative;
        overflow: hidden;
        padding: 46px 44px;
        border-radius: var(--radius-xl);
        background:
          radial-gradient(circle at 18% 12%, rgba(209, 111, 43, 0.14), transparent 22%),
          radial-gradient(circle at 84% 16%, rgba(14, 114, 120, 0.15), transparent 24%),
          linear-gradient(135deg, rgba(255, 252, 247, 0.96), rgba(255, 248, 240, 0.9));
        border: 1px solid rgba(27, 40, 48, 0.08);
        box-shadow: var(--shadow-strong);
      }

      .hero::after {
        content: "";
        position: absolute;
        right: -120px;
        top: -120px;
        width: 360px;
        height: 360px;
        border-radius: 50%;
        background: radial-gradient(circle, rgba(14, 114, 120, 0.12), transparent 68%);
        pointer-events: none;
      }

      .hero-grid {
        position: relative;
        z-index: 1;
        display: grid;
        grid-template-columns: minmax(0, 1.45fr) minmax(300px, 0.7fr);
        gap: 28px;
        align-items: end;
      }

      .hero-copy {
        max-width: 780px;
      }

      .hero-grid > *,
      .layout > *,
      .content > *,
      .subgrid > *,
      .equation-panel > *,
      .world-grid > * {
        min-width: 0;
      }

      .eyebrow {
        display: inline-flex;
        align-items: center;
        gap: 10px;
        padding: 9px 15px;
        border-radius: 999px;
        font-size: 0.78rem;
        font-weight: 800;
        letter-spacing: 0.1em;
        text-transform: uppercase;
        color: var(--accent-2);
        background: rgba(14, 114, 120, 0.1);
        border: 1px solid rgba(14, 114, 120, 0.16);
      }

      .hero h1 {
        margin: 18px 0 14px;
        max-width: 11ch;
        font-family: "Cormorant Garamond", serif;
        font-size: clamp(3.2rem, 7vw, 6.2rem);
        line-height: 0.92;
        letter-spacing: -0.04em;
      }

      .hero p {
        margin: 0;
        max-width: 64ch;
        font-size: 1.08rem;
        line-height: 1.86;
        color: var(--muted);
      }

      .quote-card {
        padding: 24px;
        border-radius: var(--radius-lg);
        color: #f8f3ea;
        background: linear-gradient(145deg, rgba(27, 40, 48, 0.96), rgba(42, 57, 68, 0.94));
        box-shadow: 0 18px 44px rgba(27, 40, 48, 0.24);
      }

      .quote-card .label {
        font-size: 0.74rem;
        font-weight: 800;
        letter-spacing: 0.08em;
        text-transform: uppercase;
        color: rgba(248, 243, 234, 0.62);
      }

      .quote-card .equation {
        margin: 16px 0 10px;
        font-size: 1.6rem;
      }

      .quote-card p {
        color: rgba(248, 243, 234, 0.76);
        font-size: 0.94rem;
        line-height: 1.78;
      }

      .hero-actions {
        display: flex;
        align-items: center;
        gap: 12px;
        flex-wrap: wrap;
        margin-top: 22px;
      }

      .inline-actions {
        display: flex;
        align-items: center;
        gap: 10px;
        flex-wrap: wrap;
      }

      .hero-note {
        font-size: 0.9rem;
        color: var(--muted);
      }

      .layout {
        display: grid;
        grid-template-columns: 260px minmax(0, 1fr);
        gap: 24px;
        margin-top: 24px;
      }

      .toc {
        position: sticky;
        top: 24px;
        align-self: start;
        padding: 18px;
        border-radius: var(--radius-lg);
        background: var(--paper);
        backdrop-filter: blur(12px);
        border: 1px solid rgba(27, 40, 48, 0.08);
        box-shadow: var(--shadow-soft);
      }

      .toc h2 {
        margin: 0 0 14px;
        font-size: 0.98rem;
        text-transform: uppercase;
        letter-spacing: 0.1em;
        color: var(--muted);
      }

      .toc nav {
        display: grid;
        gap: 10px;
      }

      .toc a {
        display: block;
        padding: 12px 14px;
        text-decoration: none;
        color: var(--ink);
        border-radius: 14px;
        font-weight: 700;
        background: rgba(255, 255, 255, 0.66);
        border: 1px solid rgba(27, 40, 48, 0.08);
      }

      .toc a:hover {
        background: rgba(209, 111, 43, 0.09);
      }

      .content {
        display: grid;
        gap: 24px;
      }

      .content > * {
        scroll-margin-top: 18px;
      }

      .chapter-index {
        margin-top: 24px;
      }

      .chapter-grid {
        display: grid;
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 18px;
        margin-top: 18px;
      }

      .chapter-card {
        padding: 20px;
        border-radius: 22px;
        background: rgba(255, 255, 255, 0.74);
        border: 1px solid rgba(27, 40, 48, 0.08);
      }

      .chapter-card h3 {
        margin: 0 0 10px;
        font-size: 1.18rem;
      }

      .chapter-card p {
        margin: 0 0 14px;
      }

      .chapter-meta {
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 12px;
        flex-wrap: wrap;
      }

      .chapter-tag {
        display: inline-flex;
        align-items: center;
        padding: 7px 12px;
        border-radius: 999px;
        font-size: 0.74rem;
        font-weight: 800;
        letter-spacing: 0.08em;
        text-transform: uppercase;
        background: rgba(14, 114, 120, 0.1);
        color: var(--accent-2);
        border: 1px solid rgba(14, 114, 120, 0.16);
      }

      .chapter-tag.soon {
        background: rgba(27, 40, 48, 0.07);
        color: var(--muted);
        border-color: rgba(27, 40, 48, 0.1);
      }

      .chapter-link {
        display: inline-flex;
        align-items: center;
        gap: 8px;
        text-decoration: none;
        font-weight: 800;
        color: var(--accent);
      }

      .chapter-link.disabled {
        color: var(--muted);
        pointer-events: none;
      }

      .chapter-intro {
        background:
          radial-gradient(circle at 84% 20%, rgba(14, 114, 120, 0.08), transparent 22%),
          linear-gradient(135deg, rgba(255, 252, 247, 0.96), rgba(255, 248, 240, 0.9));
      }

      .section-card {
        padding: 30px 30px 32px;
        border-radius: var(--radius-xl);
        background: var(--paper);
        backdrop-filter: blur(12px);
        border: 1px solid rgba(27, 40, 48, 0.08);
        box-shadow: var(--shadow-soft);
      }

      .section-card h2 {
        margin: 10px 0 16px;
        font-family: "Cormorant Garamond", serif;
        font-size: clamp(2.2rem, 4vw, 3.4rem);
        line-height: 0.98;
        letter-spacing: -0.035em;
      }

      .section-card p {
        margin: 0 0 16px;
        font-size: 1rem;
        line-height: 1.85;
        color: var(--muted);
      }

      .section-card .lede {
        font-size: 1.08rem;
        color: var(--ink);
      }

      .subgrid {
        display: grid;
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 18px;
        margin-top: 22px;
      }

      .concept-card {
        padding: 20px;
        border-radius: var(--radius-md);
        background: rgba(255, 255, 255, 0.72);
        border: 1px solid rgba(27, 40, 48, 0.08);
      }

      .concept-card h3 {
        margin: 0 0 10px;
        font-size: 1.08rem;
      }

      .concept-card p,
      .concept-card ul {
        margin: 0;
        color: var(--muted);
        line-height: 1.78;
      }

      .equation-panel {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(min(100%, 34rem), 1fr));
        gap: 18px;
        align-items: start;
        margin-top: 22px;
        padding: 22px;
        border-radius: 24px;
        background: linear-gradient(150deg, rgba(27, 40, 48, 0.96), rgba(43, 57, 67, 0.94));
        color: #f8f3ea;
      }

      .equation-panel h3 {
        margin: 0 0 8px;
        font-size: 0.88rem;
        text-transform: uppercase;
        letter-spacing: 0.1em;
        color: rgba(248, 243, 234, 0.62);
      }

      .equation-panel p {
        color: rgba(248, 243, 234, 0.78);
        margin: 0;
      }

      .equation-box {
        font-size: 1rem;
        line-height: 1.22;
        margin: 10px 0 14px;
        width: 100%;
        overflow-x: auto;
        overflow-y: hidden;
        padding-bottom: 6px;
        -webkit-overflow-scrolling: touch;
        scrollbar-width: thin;
        scrollbar-color: rgba(248, 243, 234, 0.26) transparent;
      }

      .equation-box .katex-display {
        margin: 0;
        text-align: left;
      }

      .equation-box .katex-display > .katex {
        min-width: max-content;
      }

      .equation-panel .katex-display,
      .quote-card .katex-display {
        text-align: left;
        display: block;
        padding-bottom: 4px;
      }

      .equation-box::-webkit-scrollbar {
        height: 8px;
      }

      .equation-box::-webkit-scrollbar-track {
        background: transparent;
      }

      .equation-box::-webkit-scrollbar-thumb {
        background: rgba(248, 243, 234, 0.22);
        border-radius: 999px;
      }

      .callout {
        margin-top: 22px;
        padding: 22px 22px 22px 20px;
        border-left: 4px solid var(--accent-3);
        border-radius: 18px;
        background: linear-gradient(180deg, rgba(184, 66, 31, 0.08), rgba(184, 66, 31, 0.03));
      }

      .callout h3 {
        margin: 0 0 10px;
        font-size: 1rem;
        text-transform: uppercase;
        letter-spacing: 0.08em;
        color: var(--accent-3);
      }

      .callout p,
      .callout ul {
        margin: 0;
        color: var(--muted);
        line-height: 1.8;
      }

      .callout ul {
        margin-top: 10px;
        padding-left: 18px;
      }

      .world-card {
        overflow: hidden;
        border-radius: 26px;
        border: 1px solid rgba(27, 40, 48, 0.08);
        background: rgba(255, 255, 255, 0.74);
        box-shadow: var(--shadow-soft);
      }

      .world-head {
        display: flex;
        align-items: start;
        justify-content: space-between;
        gap: 16px;
        padding: 22px 22px 18px;
        border-bottom: 1px solid rgba(27, 40, 48, 0.08);
        background: linear-gradient(180deg, rgba(255, 255, 255, 0.84), rgba(255, 255, 255, 0.56));
      }

      .world-head h3 {
        margin: 0 0 8px;
        font-size: 1.45rem;
      }

      .world-head p {
        margin: 0;
      }

      .world-actions {
        display: flex;
        flex-wrap: wrap;
        justify-content: flex-end;
        gap: 10px;
      }

      .world-body {
        padding: 22px;
      }

      .world-body p {
        margin-bottom: 14px;
      }

      .world-body ul {
        margin: 0 0 16px;
        padding-left: 20px;
        color: var(--muted);
        line-height: 1.85;
      }

      .world-grid {
        display: grid;
        grid-template-columns: 1.1fr 0.9fr;
        gap: 18px;
        margin-top: 18px;
      }

      .viz-shell {
        min-height: 330px;
        border-radius: 20px;
        overflow: hidden;
        border: 1px solid rgba(27, 40, 48, 0.08);
        background:
          radial-gradient(circle at top left, rgba(14, 114, 120, 0.12), transparent 28%),
          linear-gradient(180deg, rgba(255, 255, 255, 0.84), rgba(243, 235, 221, 0.92));
      }

      .viz-shell.viz-wide {
        min-height: 540px;
      }

      .world-side {
        display: grid;
        gap: 16px;
      }

      .stat-box {
        padding: 18px;
        border-radius: 18px;
        background: rgba(255, 255, 255, 0.74);
        border: 1px solid rgba(27, 40, 48, 0.08);
      }

      .stat-box h4 {
        margin: 0 0 8px;
        font-size: 0.86rem;
        text-transform: uppercase;
        letter-spacing: 0.08em;
        color: var(--muted);
      }

      .stat-box p {
        margin: 0;
      }

      .control-row {
        display: flex;
        align-items: center;
        gap: 14px;
        flex-wrap: wrap;
        margin-top: 14px;
      }

      .control-row label {
        font-size: 0.9rem;
        font-weight: 700;
        color: var(--muted);
      }

      .control-row input[type="range"] {
        width: min(100%, 220px);
        accent-color: var(--accent);
      }

      .btn {
        appearance: none;
        border: 0;
        cursor: pointer;
        padding: 10px 14px;
        border-radius: 999px;
        font-family: inherit;
        font-size: 0.88rem;
        font-weight: 800;
        letter-spacing: 0.03em;
        color: #fff9f1;
        background: linear-gradient(135deg, var(--accent), #e08b37);
        box-shadow: 0 12px 24px rgba(209, 111, 43, 0.24);
      }

      .btn:hover {
        filter: brightness(1.02);
      }

      .btn.secondary {
        background: linear-gradient(135deg, var(--accent-2), #1e9199);
        box-shadow: 0 12px 24px rgba(14, 114, 120, 0.24);
      }

      .mini-label {
        font-size: 0.84rem;
        color: var(--muted);
      }

      .katex-display {
        margin: 0.9em 0;
        display: block;
        overflow-x: auto;
        overflow-y: hidden;
        padding-bottom: 6px;
        max-width: 100%;
      }

      @media (max-width: 1150px) {
        .layout,
        .subgrid,
        .equation-panel,
        .world-grid,
        .chapter-grid {
          grid-template-columns: 1fr;
        }

        .hero {
          padding: 34px 32px 30px;
        }

        .hero::after {
          right: -80px;
          top: -90px;
          width: 280px;
          height: 280px;
        }

        .hero-grid {
          grid-template-columns: 1fr;
          max-width: none;
          margin: 0;
          gap: 18px;
          align-items: start;
        }

        .hero-copy {
          max-width: 760px;
        }

        .hero h1 {
          max-width: 10ch;
          font-size: clamp(3rem, 6vw, 4.9rem);
          line-height: 0.95;
        }

        .hero p {
          max-width: 42ch;
          font-size: 1.04rem;
          line-height: 1.74;
        }

        .toc {
          position: static;
        }

        .quote-card {
          max-width: 620px;
          width: 100%;
        }
      }

      @media (max-width: 920px) {
        .page {
          width: min(100vw - 10px, 100%);
          padding: 10px 0 30px;
        }

        .hero {
          padding: 28px 22px 22px;
          border-radius: 28px;
        }

        .hero::after {
          right: -56px;
          top: -54px;
          width: 220px;
          height: 220px;
          opacity: 0.72;
        }

        .hero-grid {
          gap: 14px;
        }

        .hero-copy,
        .quote-card {
          max-width: none;
        }

        .hero h1 {
          margin: 14px 0 12px;
          max-width: none;
          font-size: clamp(2.9rem, 8.2vw, 4.2rem);
          line-height: 0.93;
        }

        .hero p {
          max-width: 42ch;
          font-size: 1.08rem;
          line-height: 1.68;
        }

        .hero-actions {
          margin-top: 18px;
        }

        .quote-card {
          padding: 19px 18px 17px;
        }

        .quote-card .equation {
          font-size: 1.42rem;
        }

        .quote-card p {
          font-size: 0.99rem;
          line-height: 1.7;
        }

        .layout {
          gap: 18px;
          margin-top: 18px;
        }

        .toc {
          padding: 14px;
        }

        .toc a {
          font-size: 1rem;
        }

        .section-card {
          padding: 24px 22px 26px;
        }

        .section-card h2 {
          font-size: clamp(2.25rem, 8.4vw, 3rem);
        }

        .section-card p,
        .section-card .lede,
        .concept-card p,
        .concept-card ul,
        .callout p,
        .callout ul,
        .world-body ul,
        .stat-box p {
          font-size: 1.02rem;
          line-height: 1.74;
        }

        .concept-card h3,
        .world-head h3 {
          font-size: 1.24rem;
        }

        .world-body {
          padding: 20px;
        }

        .viz-shell {
          min-height: 286px;
        }

        .viz-shell.viz-wide {
          min-height: 520px;
        }

        .btn {
          font-size: 0.9rem;
        }
      }

      @media (max-width: 760px) {
        .page {
          width: min(100vw - 12px, 100%);
          padding: 8px 0 24px;
        }

        .hero {
          padding: 24px 20px;
          border-radius: 26px;
        }

        .hero h1 {
          margin-top: 14px;
          max-width: none;
          font-size: clamp(2.7rem, 12.8vw, 3.85rem);
          line-height: 0.94;
        }

        .hero p {
          font-size: 1.06rem;
          line-height: 1.66;
        }

        .hero-actions .btn {
          width: 100%;
          justify-content: center;
        }

        .hero-note {
          width: 100%;
        }

        .quote-card {
          padding: 18px;
          border-radius: 18px;
        }

        .quote-card .equation {
          font-size: 1.34rem;
        }

        .layout {
          gap: 16px;
          margin-top: 16px;
        }

        .toc {
          padding: 12px;
          border-radius: 18px;
        }

        .toc h2 {
          margin-bottom: 10px;
          font-size: 0.82rem;
        }

        .toc nav {
          display: flex;
          gap: 8px;
          overflow-x: auto;
          padding-bottom: 4px;
          scrollbar-width: none;
        }

        .toc nav::-webkit-scrollbar {
          display: none;
        }

        .toc a {
          white-space: nowrap;
          padding: 10px 12px;
          font-size: 0.98rem;
          border-radius: 12px;
        }

        .section-card {
          padding: 20px 18px 22px;
          border-radius: 24px;
        }

        .section-card h2 {
          font-size: clamp(2.15rem, 11vw, 3rem);
        }

        .section-card p,
        .section-card .lede {
          font-size: 1rem;
          line-height: 1.72;
        }

        .eyebrow {
          padding: 7px 12px;
          font-size: 0.7rem;
        }

        .concept-card,
        .callout,
        .stat-box {
          padding: 16px;
          border-radius: 16px;
        }

        .equation-panel {
          padding: 16px;
          border-radius: 18px;
        }

        .equation-box {
          font-size: 1rem;
        }

        .world-card {
          border-radius: 22px;
        }

        .world-head {
          flex-direction: column;
          align-items: stretch;
          gap: 12px;
          padding: 18px 18px 16px;
        }

        .world-head h3 {
          font-size: 1.3rem;
        }

        .world-body {
          padding: 18px;
        }

        .world-actions {
          width: 100%;
          justify-content: flex-start;
        }

        .viz-shell {
          min-height: 270px;
          border-radius: 16px;
        }

        .viz-shell.viz-wide {
          min-height: 640px;
        }

        .control-row {
          align-items: stretch;
          gap: 10px;
        }

        .control-row label {
          font-size: 0.84rem;
        }

        .control-row input[type="range"] {
          width: 100%;
        }

        .btn {
          width: fit-content;
          align-self: flex-start;
          padding: 9px 12px;
          font-size: 0.9rem;
        }

        .mini-label {
          font-size: 0.86rem;
        }
      }

      @media (max-width: 460px) {
        .page {
          width: min(100vw - 8px, 100%);
        }

        .hero {
          padding: 22px 16px 18px;
        }

        .hero h1 {
          font-size: clamp(2.55rem, 12.8vw, 3.35rem);
          max-width: none;
        }

        .hero p,
        .quote-card p {
          font-size: 1.02rem;
          line-height: 1.66;
        }

        .section-card {
          padding: 20px 16px 22px;
        }

        .section-card p,
        .section-card .lede {
          font-size: 0.995rem;
        }

        .world-body,
        .world-head {
          padding-left: 16px;
          padding-right: 16px;
        }

        .viz-shell {
          min-height: 248px;
        }

        .viz-shell.viz-wide {
          min-height: 540px;
        }
      }