/* ==========================================================================
   paragram.dev — Swiss editorial design system
   Palette:
     #ffffff  Grid White (background)
     #1a1a1a  Structure Black (text)
     #e0e0e0  Guide Gray (grid lines, section numbers)
     #0055ff  Index Blue (links, accents)
     #f5f5f5  Section Alternate
     #b0b0b0  Caption Gray
     #333333  Heading Dark
     #ff3366  Mark Red (sparing accent)
   ========================================================================== */

:root {
    --c-bg: #ffffff;
    --c-text: #1a1a1a;
    --c-guide: #e0e0e0;
    --c-blue: #0055ff;
    --c-alt: #f5f5f5;
    --c-caption: #b0b0b0;
    --c-heading: #333333;
    --c-red: #ff3366;

    --grid-cols: 12;
    --grid-gap: 24px;
    --grid-max: 1200px;

    --f-display: "DM Sans", "Inter", system-ui, sans-serif;
    --f-body: "IBM Plex Sans", "Inter", system-ui, sans-serif;
    --f-mono: "IBM Plex Mono", "SFMono-Regular", Menlo, monospace;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html, body {
    background: var(--c-bg);
    color: var(--c-text);
    font-family: var(--f-body);
    font-size: 16px;
    line-height: 1.7;
    font-weight: 400;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    position: relative;
    overflow-x: hidden;
}

/* ---------- Grid overlay (the visible underlying 12-col grid) ----------- */

.grid-overlay {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 1;
    opacity: 0.15;
    animation: gridFade 3s ease-out 0.4s forwards;
}

.grid-overlay::before {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: var(--grid-max);
    background-image:
        linear-gradient(to right,
            rgba(224, 224, 224, 0.9) 1px,
            transparent 1px);
    background-size: calc((100% - 11 * var(--grid-gap)) / 12 + var(--grid-gap)) 100%;
}

@keyframes gridFade {
    0%   { opacity: 0.15; }
    70%  { opacity: 0.15; }
    100% { opacity: 0.05; }
}

body.grid-active .grid-overlay {
    opacity: 0.18 !important;
    animation: none;
    transition: opacity 0.35s ease;
}

/* ---------- 12-column grid container ------------------------------------ */

.grid {
    display: grid;
    grid-template-columns: repeat(var(--grid-cols), 1fr);
    column-gap: var(--grid-gap);
    max-width: var(--grid-max);
    margin: 0 auto;
    padding: 0 32px;
    position: relative;
    z-index: 2;
}

/* ---------- Header ------------------------------------------------------ */

.page-header {
    border-bottom: 1px solid var(--c-guide);
    padding: 24px 0;
    background: var(--c-bg);
    position: relative;
    z-index: 5;
}

.masthead-mark {
    grid-column: 1 / span 3;
    display: flex;
    align-items: center;
    gap: 10px;
    font-family: var(--f-display);
    font-weight: 700;
    font-size: 1rem;
    letter-spacing: 0.02em;
    text-transform: lowercase;
}

.mark-square {
    width: 10px;
    height: 10px;
    background: var(--c-red);
    display: inline-block;
    flex: none;
}

.masthead-label {
    color: var(--c-text);
}

.masthead-nav {
    grid-column: 4 / span 6;
    display: flex;
    align-items: center;
    gap: 28px;
    font-family: var(--f-mono);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--c-heading);
}

.masthead-nav a {
    color: var(--c-heading);
    text-decoration: none;
    transition: color 0.18s ease;
}

.masthead-nav a:hover {
    color: var(--c-blue);
}

.nav-num {
    color: var(--c-caption);
    margin-right: 6px;
}

.nav-zero {
    color: var(--c-blue);
}

.masthead-meta {
    grid-column: 10 / span 3;
    display: flex;
    flex-direction: column;
    gap: 4px;
    font-family: var(--f-mono);
    font-size: 0.72rem;
    color: var(--c-caption);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

/* ---------- Hero -------------------------------------------------------- */

.hero {
    padding: 96px 0 120px;
    border-bottom: 1px solid var(--c-guide);
    position: relative;
}

.hero-domain {
    grid-column: 2 / span 5;
}

.display {
    font-family: var(--f-display);
    font-weight: 700;
    font-size: clamp(2.4rem, 6.2vw, 5rem);
    line-height: 1.02;
    letter-spacing: -0.025em;
    color: var(--c-text);
    margin-bottom: 32px;
}

.hero-subline {
    display: flex;
    flex-direction: column;
    gap: 10px;
    font-family: var(--f-mono);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.14em;
    color: var(--c-heading);
    max-width: 360px;
}

.hero-lede {
    grid-column: 7 / span 5;
    display: flex;
    flex-direction: column;
    gap: 32px;
}

.lede {
    font-family: var(--f-body);
    font-size: 1.15rem;
    line-height: 1.65;
    color: var(--c-text);
    font-weight: 400;
}

.lede em {
    font-style: italic;
    color: var(--c-blue);
    font-weight: 500;
}

.hero-meta {
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-family: var(--f-mono);
    font-size: 0.74rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--c-caption);
    padding-top: 18px;
    border-top: 1px solid var(--c-guide);
}

.hero-figure {
    grid-column: 2 / span 10;
    margin-top: 80px;
}

.hero-svg {
    width: 100%;
    height: auto;
    display: block;
}

.hero-svg-grid line {
    stroke: var(--c-guide);
    stroke-width: 1;
}

.hero-svg-blocks rect {
    fill: var(--c-text);
}

.hero-svg-marks .mark-red {
    fill: var(--c-red);
}

/* ---------- Generic section -------------------------------------------- */

.section {
    padding: 120px 0;
    position: relative;
    border-bottom: 1px solid var(--c-guide);
    transition: background 0.35s ease;
}

.section-light {
    background: var(--c-alt);
}

.sec-num {
    grid-column: 1 / span 1;
    font-family: var(--f-display);
    font-weight: 300;
    font-size: 4rem;
    line-height: 1;
    color: var(--c-guide);
    letter-spacing: -0.02em;
}

.sec-head {
    grid-column: 2 / span 5;
    display: flex;
    flex-direction: column;
    gap: 14px;
    padding-top: 14px;
}

.kicker {
    font-family: var(--f-mono);
    font-size: 0.74rem;
    text-transform: uppercase;
    letter-spacing: 0.18em;
    color: var(--c-caption);
}

.sec-title {
    font-family: var(--f-display);
    font-weight: 700;
    font-size: clamp(1.6rem, 3vw, 2.4rem);
    line-height: 1.15;
    letter-spacing: -0.018em;
    color: var(--c-heading);
}

.sec-body {
    grid-column: 2 / span 11;
    margin-top: 56px;
}

.sec-body-split {
    display: grid;
    grid-template-columns: repeat(11, 1fr);
    column-gap: var(--grid-gap);
}

.sec-body-split .col-a {
    grid-column: 1 / span 5;
    display: flex;
    flex-direction: column;
    gap: 18px;
    font-size: 1.02rem;
    color: var(--c-text);
}

.sec-body-split .col-b {
    grid-column: 6 / span 6;
}

.sec-body-wide {
    grid-column: 2 / span 11;
}

.sec-body-wide .intro {
    max-width: 720px;
    font-size: 1.05rem;
    color: var(--c-text);
    margin-bottom: 40px;
}

/* ---------- Dot leaders ------------------------------------------------- */

.leader {
    display: flex;
    align-items: flex-end;
    width: 100%;
}

.leader::after {
    content: "";
    flex-grow: 1;
    border-bottom: 1px dotted var(--c-caption);
    margin: 0 8px 0.32em;
    min-width: 24px;
}

.leader > span:first-child {
    flex-shrink: 0;
}

.leader > span:last-child {
    order: 3;
    flex-shrink: 0;
    text-align: right;
}

/* ---------- Key/value list (premise col-b) ----------------------------- */

.key-values {
    list-style: none;
    border-top: 1px solid var(--c-guide);
    padding-top: 16px;
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.key-values .leader {
    font-family: var(--f-mono);
    font-size: 0.84rem;
    color: var(--c-heading);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.key-values .leader > span:last-child {
    color: var(--c-text);
    text-transform: none;
    letter-spacing: 0;
    font-family: var(--f-body);
    font-size: 0.92rem;
}

/* ---------- Grammar table (System) ------------------------------------- */

.grammar-table {
    list-style: none;
    border-top: 1px solid var(--c-text);
}

.grammar-row {
    display: grid;
    grid-template-columns: 80px 200px 160px 1fr;
    column-gap: 24px;
    align-items: baseline;
    padding: 22px 0;
    border-bottom: 1px solid var(--c-guide);
    transition: background 0.18s ease, padding-left 0.18s ease;
}

.grammar-row:hover {
    background: rgba(0, 85, 255, 0.03);
    padding-left: 8px;
}

.g-num {
    font-family: var(--f-mono);
    font-size: 0.82rem;
    color: var(--c-blue);
    letter-spacing: 0.06em;
}

.g-name {
    font-family: var(--f-display);
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--c-text);
}

.g-cols {
    font-family: var(--f-mono);
    font-size: 0.82rem;
    color: var(--c-caption);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.g-note {
    font-size: 0.96rem;
    color: var(--c-heading);
    line-height: 1.55;
}

/* ---------- Code block (Notation) -------------------------------------- */

.codeblock {
    font-family: var(--f-mono);
    font-size: 0.86rem;
    line-height: 1.85;
    background: #ffffff;
    border: 1px solid var(--c-guide);
    border-left: 3px solid var(--c-text);
    padding: 22px 24px 22px 18px;
    color: var(--c-text);
    white-space: pre;
    overflow-x: auto;
}

.cb-line {
    display: block;
}

.cb-num {
    display: inline-block;
    width: 32px;
    color: var(--c-caption);
    user-select: none;
    margin-right: 12px;
    text-align: right;
}

.cb-key {
    color: var(--c-heading);
    font-weight: 500;
}

.cb-op {
    color: var(--c-blue);
}

.cb-arrow {
    color: var(--c-blue);
    font-weight: 500;
}

.cb-val {
    color: var(--c-text);
}

.cb-mark {
    color: var(--c-red);
    font-weight: 500;
}

.cb-meta {
    margin-top: 16px;
    display: flex;
    flex-direction: column;
    gap: 4px;
    font-family: var(--f-mono);
    font-size: 0.74rem;
    color: var(--c-caption);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

/* ---------- Diagrams (04) ---------------------------------------------- */

.diagrams {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    column-gap: var(--grid-gap);
    row-gap: 32px;
    border-top: 1px solid var(--c-text);
    padding-top: 32px;
}

.diagram {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.diagram-frame {
    background: var(--c-bg);
    border: 1px solid var(--c-guide);
    aspect-ratio: 5 / 3;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 14px;
    transition: border-color 0.2s ease;
}

.diagram:hover .diagram-frame {
    border-color: var(--c-text);
}

.d-svg {
    width: 100%;
    height: 100%;
    display: block;
}

.d-svg rect,
.d-svg circle {
    fill: var(--c-text);
}

.d-svg .d-axis {
    stroke: var(--c-text);
    stroke-width: 1;
    fill: none;
}

.diagram figcaption {
    display: grid;
    grid-template-columns: auto auto 1fr;
    column-gap: 12px;
    align-items: baseline;
    padding-top: 10px;
    border-top: 1px solid var(--c-guide);
}

.d-num {
    font-family: var(--f-mono);
    font-size: 0.74rem;
    color: var(--c-blue);
    letter-spacing: 0.08em;
}

.d-name {
    font-family: var(--f-display);
    font-weight: 700;
    font-size: 0.95rem;
    color: var(--c-text);
}

.d-note {
    font-size: 0.82rem;
    color: var(--c-caption);
    line-height: 1.5;
    text-align: right;
}

/* ---------- Index (05) ------------------------------------------------- */

.index-cols {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    column-gap: 64px;
    row-gap: 0;
    border-top: 1px solid var(--c-text);
    padding-top: 12px;
}

.index-list {
    list-style: none;
    display: flex;
    flex-direction: column;
}

.index-item {
    padding: 14px 0;
    border-bottom: 1px solid var(--c-guide);
    font-family: var(--f-display);
    font-size: 1.02rem;
    color: var(--c-text);
    transition: color 0.18s ease, padding-left 0.18s ease;
    cursor: default;
}

.index-item:hover {
    color: var(--c-blue);
    padding-left: 6px;
}

.ix-num {
    display: inline-block;
    min-width: 32px;
    font-family: var(--f-mono);
    font-size: 0.82rem;
    color: var(--c-caption);
    margin-right: 14px;
    letter-spacing: 0.06em;
}

.index-item .leader::after {
    border-bottom-color: var(--c-caption);
}

.index-item > span:last-child {
    font-family: var(--f-mono);
    font-size: 0.82rem;
    color: var(--c-caption);
    letter-spacing: 0.04em;
}

/* ---------- Footer ------------------------------------------------------ */

.page-footer {
    background: var(--c-text);
    color: var(--c-bg);
    padding: 80px 0 64px;
    position: relative;
    z-index: 5;
}

.page-footer .grid {
    row-gap: 32px;
}

.footer-mark {
    grid-column: 1 / span 4;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.footer-domain {
    font-family: var(--f-display);
    font-weight: 700;
    font-size: 1.5rem;
    color: var(--c-bg);
}

.footer-tagline {
    font-family: var(--f-mono);
    font-size: 0.76rem;
    color: var(--c-caption);
    text-transform: uppercase;
    letter-spacing: 0.14em;
}

.footer-meta {
    grid-column: 5 / span 4;
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-family: var(--f-mono);
    font-size: 0.78rem;
    color: var(--c-caption);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.footer-meta .leader::after {
    border-bottom-color: rgba(176, 176, 176, 0.4);
}

.footer-meta .leader > span:last-child {
    color: var(--c-bg);
}

.footer-colophon {
    grid-column: 9 / span 4;
    font-family: var(--f-body);
    font-size: 0.95rem;
    line-height: 1.7;
    color: rgba(255, 255, 255, 0.78);
    border-top: 1px solid rgba(224, 224, 224, 0.25);
    padding-top: 14px;
}

/* ---------- Responsive -------------------------------------------------- */

@media (max-width: 960px) {
    .grid {
        padding: 0 24px;
    }

    .masthead-mark { grid-column: 1 / span 6; }
    .masthead-nav  { grid-column: 1 / span 12; flex-wrap: wrap; gap: 16px; margin-top: 16px; }
    .masthead-meta { grid-column: 1 / span 12; flex-direction: row; flex-wrap: wrap; gap: 18px; margin-top: 12px; }
    .masthead-meta .leader { width: 240px; }

    .hero { padding: 64px 0 88px; }
    .hero-domain { grid-column: 1 / span 12; }
    .hero-lede   { grid-column: 1 / span 12; margin-top: 40px; }
    .hero-figure { grid-column: 1 / span 12; margin-top: 56px; }

    .section { padding: 80px 0; }
    .sec-num  { grid-column: 1 / span 12; font-size: 3rem; margin-bottom: 12px; }
    .sec-head { grid-column: 1 / span 12; }
    .sec-body { grid-column: 1 / span 12; margin-top: 32px; }

    .sec-body-split { grid-template-columns: 1fr; row-gap: 32px; }
    .sec-body-split .col-a,
    .sec-body-split .col-b { grid-column: 1 / -1; }

    .grammar-row {
        grid-template-columns: 60px 1fr 100px;
        row-gap: 6px;
    }
    .g-note { grid-column: 1 / -1; }

    .diagrams { grid-template-columns: repeat(2, 1fr); }

    .index-cols { grid-template-columns: 1fr; column-gap: 0; }

    .footer-mark,
    .footer-meta,
    .footer-colophon { grid-column: 1 / -1; }
}

@media (max-width: 560px) {
    .diagrams { grid-template-columns: 1fr; }
    .display { font-size: clamp(2rem, 9vw, 3rem); }
    .grammar-row {
        grid-template-columns: 50px 1fr;
    }
    .g-cols, .g-note { grid-column: 1 / -1; }
}