:root {
    --bg: #f5efe4;
    --bg-soft: #f9f5ee;
    --surface: rgba(255, 251, 243, 0.92);
    --surface-strong: rgba(239, 247, 246, 0.9);
    --ink: #13252b;
    --ink-soft: #36535d;
    --muted: #647780;
    --line: rgba(19, 37, 43, 0.1);
    --teal: #1f6b73;
    --teal-deep: #134b56;
    --mint: #8ee8d1;
    --gold: #f2bc6c;
    --gold-deep: #cf8f32;
    --shadow: 0 26px 70px rgba(24, 46, 49, 0.12);
    --radius-xl: 34px;
    --radius-lg: 26px;
    --radius-md: 18px;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: "IBM Plex Sans JP", sans-serif;
    color: var(--ink);
    background:
        radial-gradient(circle at top left, rgba(142, 232, 209, 0.28), transparent 32%),
        radial-gradient(circle at top right, rgba(242, 188, 108, 0.24), transparent 26%),
        linear-gradient(180deg, #f7f1e7 0%, #f2ebdf 52%, #efe9df 100%);
}

a {
    color: inherit;
    text-decoration: none;
}

button,
input {
    font: inherit;
}

.page-shell {
    width: min(1180px, calc(100% - 32px));
    margin: 0 auto;
    padding: 18px 0 56px;
}

.site-header {
    position: sticky;
    top: 14px;
    z-index: 20;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 18px;
    padding: 14px 18px;
    margin-bottom: 18px;
    border: 1px solid rgba(255, 255, 255, 0.62);
    border-radius: 999px;
    background: rgba(255, 251, 245, 0.78);
    backdrop-filter: blur(18px);
    box-shadow: 0 20px 44px rgba(22, 42, 44, 0.08);
}

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

.site-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.site-nav a {
    padding: 8px 14px;
    border-radius: 999px;
    color: var(--ink-soft);
    transition: background-color 160ms ease, color 160ms ease, transform 160ms ease;
}

.site-nav a:hover,
.site-nav a:focus-visible {
    background: rgba(19, 107, 115, 0.1);
    color: var(--teal-deep);
    transform: translateY(-1px);
}

.section {
    margin-top: 26px;
    padding: 34px;
    border: 1px solid rgba(255, 255, 255, 0.62);
    border-radius: var(--radius-xl);
    background: rgba(255, 250, 243, 0.84);
    box-shadow: var(--shadow);
}

.hero {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(420px, 0.98fr);
    gap: 24px;
    align-items: stretch;
    padding: 30px;
}

.hero-copy,
.hero-panel {
    min-width: 0;
}

.hero-copy {
    padding: 16px 6px 10px 8px;
}

.eyebrow,
.card-label,
.note-label,
.signal-kicker,
.band-title,
.summary-title {
    margin: 0;
    font-size: 0.84rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--teal);
}

.hero h1,
.section-heading h2,
.hero-note h2,
.link-card h3,
.point-card h3,
.reason-card h3,
.formula-card h3,
.error-card h3,
.tool-card h3,
.distribution-card h3 {
    margin: 0;
    font-family: "Shippori Mincho", serif;
    font-weight: 700;
    line-height: 1.24;
}

.hero h1 {
    margin-top: 14px;
    font-size: clamp(2.55rem, 5vw, 4.7rem);
}

.hero-lead,
.section-heading p,
.hero-note p,
.point-card p,
.reason-card p,
.formula-card p,
.error-card p,
.tool-card p,
.distribution-card p,
.link-card p,
.hero-summary p,
.signal-sub,
.canvas-caption,
.demo-note,
.site-footer p {
    color: var(--ink-soft);
    line-height: 1.85;
}

.hero-lead {
    margin: 18px 0 0;
    font-size: 1.02rem;
}

.hero-actions,
.button-row,
.footer-links {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.hero-actions {
    margin-top: 24px;
}

.button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    padding: 0 18px;
    border-radius: 999px;
    border: 1px solid transparent;
    font-weight: 700;
    transition: transform 160ms ease, box-shadow 160ms ease, background-color 160ms ease, color 160ms ease;
}

.button:hover,
.button:focus-visible {
    transform: translateY(-1px);
}

.button-primary {
    background: linear-gradient(135deg, var(--teal) 0%, #2a8b84 100%);
    color: #f5fffe;
    box-shadow: 0 14px 30px rgba(31, 107, 115, 0.22);
}

.button-secondary {
    border-color: rgba(19, 37, 43, 0.12);
    background: rgba(255, 251, 244, 0.82);
    color: var(--ink);
}

.hero-points {
    display: grid;
    gap: 12px;
    margin: 24px 0 0;
    padding: 0;
    list-style: none;
}

.hero-points li {
    position: relative;
    padding-left: 22px;
    color: var(--ink-soft);
}

.hero-points li::before {
    content: "";
    position: absolute;
    top: 0.76em;
    left: 0;
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--gold) 0%, var(--teal) 100%);
}

.hero-panel {
    display: grid;
    gap: 18px;
}

.measurement-window,
.hero-note,
.hero-summary,
.point-card,
.reason-card,
.formula-card,
.error-card,
.distribution-card,
.tool-card,
.demo-panel,
.chart-panel,
.link-card,
.contrast-panel,
.prop-demo-panel,
.formula-panel,
.stat-grid article,
.coverage-grid article {
    border: 1px solid rgba(22, 48, 51, 0.08);
    border-radius: var(--radius-lg);
    background: linear-gradient(180deg, rgba(255, 252, 247, 0.96), rgba(242, 248, 247, 0.86));
    box-shadow: 0 16px 34px rgba(24, 45, 47, 0.08);
}

.warm-note,
.warm-card {
    background: linear-gradient(180deg, rgba(255, 247, 235, 0.98), rgba(255, 237, 209, 0.84));
}

.strong-note,
.strong-card {
    background: linear-gradient(180deg, rgba(239, 249, 248, 0.98), rgba(224, 241, 239, 0.84));
}

.measurement-window {
    padding: 18px;
    background:
        linear-gradient(180deg, rgba(16, 25, 31, 0.94), rgba(29, 44, 55, 0.96)),
        linear-gradient(160deg, rgba(142, 232, 209, 0.18), transparent 40%);
    color: #edf5f6;
}

.window-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
}

.window-head span {
    color: rgba(255, 255, 255, 0.62);
    font-size: 0.82rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.window-head strong {
    font-size: 1.02rem;
}

.sample-ribbon {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.sample-ribbon span {
    padding: 8px 10px;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.08);
    color: rgba(255, 255, 255, 0.9);
    font-size: 0.94rem;
}

.distribution-board {
    margin-top: 16px;
    padding: 16px;
    border-radius: 22px;
    background: rgba(255, 255, 255, 0.04);
}

.distribution-board p {
    margin: 18px 0 0;
    color: rgba(255, 255, 255, 0.76);
    line-height: 1.8;
}

.distribution-axis {
    position: relative;
    height: 128px;
    border-radius: 18px;
    background:
        linear-gradient(180deg, rgba(142, 232, 209, 0.1), rgba(142, 232, 209, 0.02)),
        linear-gradient(180deg, rgba(255, 255, 255, 0.04), rgba(255, 255, 255, 0.01));
    overflow: hidden;
}

.distribution-axis::before {
    content: "";
    position: absolute;
    inset: auto 18px 24px;
    height: 1px;
    background: rgba(255, 255, 255, 0.18);
}

.axis-label,
.distribution-dot,
.mean-pill {
    position: absolute;
}

.axis-label {
    bottom: 6px;
    font-size: 0.8rem;
    color: rgba(255, 255, 255, 0.58);
}

.axis-left {
    left: 18px;
}

.axis-right {
    right: 18px;
}

.distribution-dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: radial-gradient(circle at 30% 30%, #fff4cf 0%, var(--gold) 50%, #bf7a1b 100%);
    box-shadow: 0 0 0 4px rgba(242, 188, 108, 0.16);
}

.dot-a { left: 26%; top: 58px; }
.dot-b { left: 34%; top: 76px; }
.dot-c { left: 39%; top: 46px; }
.dot-d { left: 45%; top: 34px; }
.dot-e { left: 50%; top: 40px; }
.dot-f { left: 54%; top: 64px; }
.dot-g { left: 60%; top: 52px; }
.dot-h { left: 66%; top: 70px; }

.mean-pill {
    left: 43%;
    top: 12px;
    padding: 6px 12px;
    border-radius: 999px;
    background: rgba(142, 232, 209, 0.18);
    color: #e9fffb;
    font-weight: 700;
}

.hero-note-grid,
.why-grid,
.distribution-grid,
.demo-grid,
.propagation-grid,
.link-grid {
    display: grid;
    gap: 18px;
}

.hero-note-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

.hero-note,
.hero-summary,
.point-card,
.reason-card,
.formula-card,
.error-card,
.tool-card,
.distribution-card,
.demo-panel,
.chart-panel,
.link-card,
.contrast-panel,
.prop-demo-panel,
.formula-panel {
    padding: 22px;
}

.hero-summary {
    padding-top: 18px;
}

.summary-title {
    margin-bottom: 8px;
}

.signal-strip {
    display: grid;
    gap: 8px;
    margin-top: 26px;
    padding: 24px 30px;
    border-radius: var(--radius-xl);
    background: linear-gradient(135deg, rgba(18, 69, 82, 0.98), rgba(34, 108, 107, 0.94));
    color: #efffff;
    box-shadow: 0 24px 46px rgba(22, 53, 60, 0.18);
}

.signal-main {
    margin: 0;
    font-family: "Shippori Mincho", serif;
    font-size: clamp(1.45rem, 2.7vw, 2.35rem);
    line-height: 1.4;
}

.signal-strip .signal-kicker,
.signal-strip .signal-sub {
    color: rgba(241, 255, 254, 0.82);
}

.section-heading {
    display: grid;
    gap: 10px;
    margin-bottom: 24px;
}

.section-heading h2 {
    font-size: clamp(1.7rem, 3.2vw, 2.8rem);
}

.section-heading p {
    margin: 0;
    max-width: 800px;
}

.why-grid {
    grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);
    align-items: start;
}

.reason-stack,
.core-grid,
.error-grid,
.tool-grid,
.formula-ladder {
    display: grid;
    gap: 16px;
}

.core-grid,
.error-grid,
.tool-grid,
.link-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.contrast-panel {
    display: grid;
    grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);
    gap: 18px;
    margin-top: 18px;
}

.spread-comparison {
    display: grid;
    gap: 16px;
}

.spread-case {
    padding: 16px;
    border-radius: 18px;
    background: rgba(19, 107, 115, 0.05);
}

.case-label {
    display: block;
    margin-bottom: 10px;
    font-weight: 700;
    color: var(--ink-soft);
}

.spread-line {
    position: relative;
    height: 64px;
    border-radius: 16px;
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.6), rgba(236, 242, 241, 0.7));
}

.spread-line::before {
    content: "";
    position: absolute;
    inset: auto 16px 18px;
    height: 1px;
    background: rgba(19, 37, 43, 0.16);
}

.spread-line span {
    position: absolute;
    bottom: 13px;
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: var(--teal);
}

.narrow-case .spread-line span:nth-child(1) { left: 38%; }
.narrow-case .spread-line span:nth-child(2) { left: 43%; }
.narrow-case .spread-line span:nth-child(3) { left: 46%; }
.narrow-case .spread-line span:nth-child(4) { left: 50%; }
.narrow-case .spread-line span:nth-child(5) { left: 53%; }
.narrow-case .spread-line span:nth-child(6) { left: 58%; }

.wide-case .spread-line span:nth-child(1) { left: 18%; }
.wide-case .spread-line span:nth-child(2) { left: 31%; }
.wide-case .spread-line span:nth-child(3) { left: 43%; }
.wide-case .spread-line span:nth-child(4) { left: 56%; }
.wide-case .spread-line span:nth-child(5) { left: 68%; }
.wide-case .spread-line span:nth-child(6) { left: 80%; }

.error-conclusion {
    margin-top: 16px;
    color: var(--teal-deep);
    font-weight: 700;
}

.distribution-grid {
    grid-template-columns: minmax(0, 0.96fr) minmax(0, 1.04fr);
}

.bell-curve {
    position: relative;
    height: 220px;
    margin-top: 18px;
    border-radius: 22px;
    overflow: hidden;
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.5), rgba(241, 247, 246, 0.78)),
        linear-gradient(180deg, rgba(31, 107, 115, 0.08), transparent);
}

.bell-curve::before,
.bell-curve::after {
    content: "";
    position: absolute;
    left: 26px;
    right: 26px;
    border-top: 1px solid rgba(19, 37, 43, 0.1);
}

.bell-curve::before {
    bottom: 34px;
}

.bell-curve::after {
    top: 28px;
    opacity: 0.16;
}

.curve-fill {
    position: absolute;
    inset: 28px 20px 34px;
    background: linear-gradient(180deg, rgba(31, 107, 115, 0.22), rgba(31, 107, 115, 0.06));
    clip-path: path("M 20 158 C 80 154 110 94 155 48 C 202 6 300 6 347 48 C 392 94 422 154 482 158 L 482 158 L 482 186 L 20 186 Z");
}

.curve-marker {
    position: absolute;
    bottom: 10px;
    transform: translateX(-50%);
    font-size: 0.82rem;
    color: var(--muted);
}

.marker-minus-two { left: 18%; }
.marker-minus-one { left: 34%; }
.marker-zero { left: 50%; }
.marker-plus-one { left: 66%; }
.marker-plus-two { left: 82%; }

.coverage-grid,
.stat-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px;
}

.coverage-grid {
    margin-top: 16px;
}

.coverage-grid article,
.stat-grid article {
    padding: 16px 18px;
}

.coverage-grid span,
.stat-grid span {
    color: var(--muted);
    font-size: 0.9rem;
}

.coverage-grid strong,
.stat-grid strong {
    display: block;
    margin-top: 8px;
    font-size: 1.1rem;
}

.demo-grid,
.propagation-grid {
    grid-template-columns: minmax(0, 0.98fr) minmax(0, 1.02fr);
    align-items: start;
}

.control {
    display: grid;
    gap: 8px;
}

.control + .control {
    margin-top: 16px;
}

.control span {
    color: var(--teal-deep);
    font-weight: 700;
}

.control strong {
    color: var(--ink);
}

.control input {
    width: 100%;
    accent-color: var(--teal);
}

.demo-note,
.canvas-caption {
    margin: 18px 0 0;
}

#measurementCanvas {
    width: 100%;
    height: auto;
    border-radius: 26px;
    background: linear-gradient(180deg, rgba(10, 15, 22, 0.98), rgba(24, 38, 50, 0.98));
    border: 1px solid rgba(255, 255, 255, 0.08);
    box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.03);
}

.sample-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 18px;
}

.sample-chip {
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(19, 107, 115, 0.08);
    color: var(--ink-soft);
    font-size: 0.94rem;
}

.formula-block {
    margin: 14px 0 0;
    padding: 16px 18px;
    border-radius: 20px;
    background: rgba(18, 69, 82, 0.08);
    color: var(--ink);
    font-size: clamp(1rem, 1.7vw, 1.22rem);
    line-height: 1.7;
}

.formula-block.multiline {
    display: grid;
    gap: 8px;
}

.prop-demo-panel {
    display: grid;
    gap: 18px;
}

.prop-controls,
.prop-results {
    display: grid;
    gap: 16px;
}

.contribution-grid {
    display: grid;
    gap: 14px;
}

.contribution-row {
    display: grid;
    grid-template-columns: 98px minmax(0, 1fr) 58px;
    align-items: center;
    gap: 12px;
}

.contribution-row span,
.contribution-row strong {
    color: var(--ink-soft);
}

.contribution-bar {
    position: relative;
    height: 14px;
    border-radius: 999px;
    overflow: hidden;
    background: rgba(19, 107, 115, 0.12);
}

.contribution-bar span {
    position: absolute;
    inset: 0 auto 0 0;
    width: 50%;
    border-radius: 999px;
    background: linear-gradient(90deg, var(--teal) 0%, var(--mint) 100%);
}

.warm-bar span {
    background: linear-gradient(90deg, var(--gold-deep) 0%, var(--gold) 100%);
}

.link-card {
    display: grid;
    gap: 8px;
    transition: transform 180ms ease, box-shadow 180ms ease;
}

.link-card:hover,
.link-card:focus-visible {
    transform: translateY(-3px);
    box-shadow: 0 24px 44px rgba(23, 45, 47, 0.14);
}

.site-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 18px;
    margin-top: 28px;
    padding: 24px 28px;
    border-radius: var(--radius-xl);
    background: rgba(18, 28, 35, 0.92);
    color: rgba(255, 255, 255, 0.86);
    box-shadow: 0 18px 38px rgba(17, 35, 39, 0.2);
}

.site-footer p {
    margin: 0;
    color: rgba(255, 255, 255, 0.76);
}

.footer-links a {
    color: rgba(255, 255, 255, 0.9);
}

.reveal {
    opacity: 0;
    transform: translateY(22px);
    transition: opacity 500ms ease, transform 500ms ease;
}

.reveal.is-visible {
    opacity: 1;
    transform: translateY(0);
}

@media (max-width: 1080px) {
    .hero,
    .why-grid,
    .distribution-grid,
    .demo-grid,
    .propagation-grid,
    .contrast-panel {
        grid-template-columns: 1fr;
    }

    .core-grid,
    .error-grid,
    .tool-grid,
    .link-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (max-width: 760px) {
    .page-shell {
        width: min(100% - 18px, 100%);
        padding-top: 10px;
    }

    .site-header,
    .site-footer {
        border-radius: 28px;
    }

    .site-header,
    .site-footer,
    .section,
    .hero {
        padding-left: 18px;
        padding-right: 18px;
    }

    .section {
        padding-top: 24px;
        padding-bottom: 24px;
    }

    .site-header,
    .site-footer {
        flex-direction: column;
        align-items: stretch;
    }

    .site-nav,
    .footer-links,
    .hero-note-grid,
    .core-grid,
    .error-grid,
    .tool-grid,
    .link-grid,
    .coverage-grid,
    .stat-grid {
        grid-template-columns: 1fr;
    }

    .hero-note-grid,
    .core-grid,
    .error-grid,
    .tool-grid,
    .link-grid,
    .coverage-grid,
    .stat-grid {
        display: grid;
    }

    .contribution-row {
        grid-template-columns: 1fr;
    }

    .curve-fill {
        clip-path: path("M 12 158 C 68 154 100 96 147 52 C 194 12 286 12 333 52 C 380 96 412 154 468 158 L 468 158 L 468 188 L 12 188 Z");
    }
}