/* =========================================================
   undo.systems — isometric technical docs
   Palette
     #0a1628  Blueprint (deep navy)
     #1a2d4a  Grid line / panel border
     #c8d6e5  Reading text
     #3498db  System Blue (components)
     #2ecc71  Rollback Green (committed)
     #e74c3c  Fault Red (failed)
     #7f8c8d  Connection (diagram lines)
   Fonts: IBM Plex Sans, IBM Plex Mono
   ========================================================= */

*,
*::before,
*::after {
    box-sizing: border-box;
}

:root {
    --c-blueprint: #0a1628;
    --c-grid: #1a2d4a;
    --c-text: #c8d6e5;
    --c-blue: #3498db;
    --c-green: #2ecc71;
    --c-red: #e74c3c;
    --c-conn: #7f8c8d;

    --c-text-dim: rgba(200, 214, 229, 0.55);
    --c-panel: rgba(10, 22, 40, 0.55);
    --c-panel-strong: rgba(10, 22, 40, 0.78);
    --c-blue-glow: rgba(52, 152, 219, 0.1);
    --c-blue-glow-2: rgba(52, 152, 219, 0.18);
    --c-blue-line: rgba(52, 152, 219, 0.35);

    --font-sans: "IBM Plex Sans", "Inter", system-ui, -apple-system, Segoe UI, sans-serif;
    --font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

    --rad: 4px;
    --grid-step: 40px;
}

html,
body {
    margin: 0;
    padding: 0;
}

html {
    background: var(--c-blueprint);
    color: var(--c-text);
}

body {
    font-family: var(--font-sans);
    font-weight: 400;
    font-size: 16px;
    line-height: 1.65;
    background: var(--c-blueprint);
    color: var(--c-text);
    min-height: 100vh;
    overflow-x: hidden;
    position: relative;
}

/* ---------- Blueprint grid background ---------- */
.blueprint-bg {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    background-color: var(--c-blueprint);
    background-image:
        linear-gradient(var(--c-grid) 1px, transparent 1px),
        linear-gradient(90deg, var(--c-grid) 1px, transparent 1px);
    background-size: var(--grid-step) var(--grid-step);
    opacity: 0.5;
}

.blueprint-bg::after {
    content: "";
    position: absolute;
    inset: 0;
    background:
        radial-gradient(ellipse at 20% 0%, rgba(52, 152, 219, 0.08), transparent 60%),
        radial-gradient(ellipse at 80% 100%, rgba(46, 204, 113, 0.05), transparent 55%);
    pointer-events: none;
}

/* ---------- Header ---------- */
.site-header {
    position: relative;
    z-index: 5;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1.5rem;
    padding: 1rem 2rem;
    border-bottom: 1px solid var(--c-grid);
    background: rgba(10, 22, 40, 0.85);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    font-family: var(--font-mono);
    font-size: 0.78rem;
}

.brand {
    display: flex;
    align-items: baseline;
    gap: 0.75rem;
}

.brand-mark {
    color: var(--c-blue);
    font-weight: 500;
    letter-spacing: 0.05em;
}

.brand-name {
    font-family: var(--font-sans);
    font-weight: 600;
    color: var(--c-text);
    font-size: 1rem;
    letter-spacing: 0.02em;
}

.brand-tag {
    color: var(--c-text-dim);
    font-size: 0.72rem;
    letter-spacing: 0.06em;
    text-transform: lowercase;
}

.meta-nav {
    display: flex;
    align-items: center;
    gap: 1.25rem;
    color: var(--c-text-dim);
    font-size: 0.72rem;
    letter-spacing: 0.05em;
}

.meta-status {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--c-text);
}

.meta-build,
.meta-doc {
    color: var(--c-text-dim);
}

/* ---------- Layout ---------- */
.layout {
    position: relative;
    z-index: 1;
    display: grid;
    grid-template-columns: 240px 1fr;
    max-width: 1200px;
    margin: 0 auto;
    gap: 0;
}

/* ---------- Sidebar ---------- */
.sidebar {
    position: sticky;
    top: 0;
    align-self: start;
    height: 100vh;
    overflow-y: auto;
    border-right: 1px solid var(--c-grid);
    padding: 2rem 1.25rem 2rem 1.5rem;
    background: linear-gradient(
        180deg,
        rgba(10, 22, 40, 0.6) 0%,
        rgba(10, 22, 40, 0.85) 100%
    );
    font-family: var(--font-mono);
    font-size: 0.82rem;
}

.sidebar-title {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    padding-bottom: 0.75rem;
    border-bottom: 1px dashed var(--c-grid);
    margin-bottom: 1rem;
}

.sidebar-section {
    color: var(--c-blue);
    letter-spacing: 0.12em;
    font-size: 0.7rem;
}

.sidebar-version {
    color: var(--c-text-dim);
    font-size: 0.7rem;
}

.tree {
    list-style: none;
    margin: 0;
    padding: 0;
}

.tree-node {
    padding: 0.18rem 0;
    color: var(--c-text);
}

.tree-node a {
    color: inherit;
    text-decoration: none;
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
    padding: 0.18rem 0.4rem;
    border-radius: var(--rad);
    transition: background-color 160ms ease, color 160ms ease;
}

.tree-node a:hover {
    background: var(--c-blue-glow);
    color: var(--c-blue);
}

.tree-node.is-active a {
    background: var(--c-blue-glow-2);
    color: var(--c-blue);
}

.tree-key {
    color: var(--c-blue);
    font-size: 0.7rem;
    min-width: 1.5rem;
    letter-spacing: 0.05em;
}

.tree-label {
    font-family: var(--font-sans);
    font-size: 0.86rem;
}

.tree-root {
    color: var(--c-text-dim);
    margin-bottom: 0.4rem;
    font-size: 0.78rem;
}

.tree-root .tree-key {
    color: var(--c-text-dim);
}

.tree-l2 {
    padding-left: 1.3rem;
    font-size: 0.74rem;
    color: var(--c-text-dim);
}

.tree-l2 a {
    color: var(--c-text-dim);
}

.tree-l2 a:hover {
    color: var(--c-text);
}

.sidebar-legend {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px dashed var(--c-grid);
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    font-size: 0.74rem;
    color: var(--c-text-dim);
}

.legend-title {
    color: var(--c-blue);
    letter-spacing: 0.12em;
    font-size: 0.68rem;
    margin-bottom: 0.3rem;
}

.legend-item {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--c-text);
    font-size: 0.78rem;
}

/* ---------- Content ---------- */
.content {
    padding: 3rem 2.5rem 4rem;
    min-width: 0;
}

.section {
    margin-bottom: 4rem;
    scroll-margin-top: 80px;
}

.section-header {
    display: grid;
    grid-template-columns: 60px 1fr;
    gap: 1.25rem;
    align-items: start;
    margin-bottom: 1.75rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--c-grid);
}

.section-num {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--c-blue);
    letter-spacing: 0.1em;
    padding-top: 0.55rem;
    border-right: 1px dashed var(--c-grid);
    padding-right: 0.75rem;
    text-align: right;
}

.section-title {
    font-family: var(--font-sans);
    font-weight: 600;
    font-size: clamp(1.5rem, 2.5vw, 2rem);
    line-height: 1.2;
    margin: 0 0 0.4rem;
    color: var(--c-text);
    letter-spacing: -0.01em;
}

.section-sub {
    margin: 0;
    color: var(--c-text-dim);
    font-size: 0.95rem;
    max-width: 64ch;
}

.section-sub em {
    color: var(--c-text);
    font-style: italic;
}

/* ---------- Hero ---------- */
.section-hero .section-title {
    font-size: clamp(1.9rem, 3.4vw, 2.6rem);
}

.hero-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.card {
    position: relative;
    background: var(--c-blue-glow);
    border: 1px solid var(--c-blue);
    border-radius: var(--rad);
    padding: 1rem 1rem 0.85rem;
    display: flex;
    flex-direction: column;
    min-height: 175px;
    transition: transform 240ms ease, border-color 240ms ease, background 240ms ease;
}

.card:hover {
    transform: translateY(-2px);
    background: var(--c-blue-glow-2);
}

.card-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-blue);
    letter-spacing: 0.1em;
    margin-bottom: 0.5rem;
}

.card-tag {
    background: rgba(52, 152, 219, 0.18);
    padding: 0.1rem 0.4rem;
    border-radius: 2px;
}

.card-id {
    color: var(--c-text-dim);
}

.card-title {
    font-size: 1.05rem;
    font-weight: 600;
    margin: 0 0 0.4rem;
    color: var(--c-text);
}

.card-body {
    margin: 0;
    font-size: 0.88rem;
    color: var(--c-text-dim);
    flex: 1;
}

.card-body code,
.card code {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--c-blue);
    background: transparent;
    padding: 0 0.1rem;
}

.card-foot {
    margin-top: 0.6rem;
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-family: var(--font-mono);
    font-size: 0.72rem;
    color: var(--c-text-dim);
    letter-spacing: 0.05em;
    border-top: 1px dashed var(--c-grid);
    padding-top: 0.5rem;
}

/* ---------- Hero strip ---------- */
.hero-strip {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    background: var(--c-panel);
}

.strip-cell {
    padding: 0.85rem 1rem;
    border-right: 1px dashed var(--c-grid);
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
}

.strip-cell:last-child {
    border-right: 0;
}

.strip-num {
    font-family: var(--font-mono);
    font-size: 1.4rem;
    font-weight: 500;
    color: var(--c-blue);
    letter-spacing: 0.02em;
}

.strip-label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.08em;
    text-transform: lowercase;
}

/* ---------- Primitives ---------- */
.prim-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1rem;
}

.prim {
    background: var(--c-panel);
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    padding: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    transition: border-color 220ms ease, background 220ms ease;
}

.prim:hover {
    border-color: var(--c-blue);
    background: rgba(52, 152, 219, 0.06);
}

.prim-icon {
    width: 64px;
    height: 64px;
    border: 1px dashed var(--c-grid);
    border-radius: var(--rad);
    display: grid;
    place-items: center;
    background: rgba(10, 22, 40, 0.4);
}

.prim-icon svg {
    width: 80%;
    height: 80%;
}

.prim-title {
    font-size: 1rem;
    font-weight: 600;
    margin: 0;
    color: var(--c-text);
}

.prim-body {
    margin: 0;
    font-size: 0.88rem;
    color: var(--c-text-dim);
    flex: 1;
}

.prim-body code {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--c-blue);
}

.prim-sig {
    display: inline-block;
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--c-blue);
    background: rgba(52, 152, 219, 0.08);
    border: 1px dashed var(--c-blue-line);
    border-radius: var(--rad);
    padding: 0.25rem 0.5rem;
    align-self: flex-start;
    letter-spacing: 0.02em;
}

/* ---------- Diagram ---------- */
.diagram {
    position: relative;
    margin: 0;
    padding: 1.25rem;
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    background: var(--c-panel);
    overflow: hidden;
}

.diagram::before {
    content: "FIG.03";
    position: absolute;
    top: 0.6rem;
    right: 0.85rem;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.1em;
}

.diagram-svg {
    display: block;
    width: 100%;
    height: 460px;
    pointer-events: none;
}

.diagram-caption {
    margin-top: 0.5rem;
    font-family: var(--font-mono);
    font-size: 0.74rem;
    color: var(--c-text-dim);
    letter-spacing: 0.04em;
    text-align: center;
}

.node {
    position: absolute;
    left: var(--x);
    top: var(--y);
    width: 140px;
    background: var(--c-blue-glow);
    border: 1px solid var(--c-blue);
    border-radius: var(--rad);
    padding: 0.6rem 0.75rem;
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
    transition: background 220ms ease, transform 220ms ease, box-shadow 220ms ease;
    z-index: 2;
}

.node.is-active {
    background: var(--c-blue-glow-2);
    box-shadow: 0 0 0 1px var(--c-blue), 0 0 20px rgba(52, 152, 219, 0.3);
    transform: translateY(-2px);
}

.node-tag {
    font-family: var(--font-mono);
    font-size: 0.65rem;
    color: var(--c-blue);
    letter-spacing: 0.12em;
}

.node-name {
    font-family: var(--font-mono);
    font-size: 0.86rem;
    font-weight: 500;
    color: var(--c-text);
}

.node-meta {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.04em;
}

/* ---------- Spec table ---------- */
.table-wrap {
    overflow-x: auto;
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    background: var(--c-panel);
}

.spec-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.88rem;
}

.spec-table thead th {
    background: var(--c-blue-glow-2);
    color: var(--c-blue);
    font-family: var(--font-mono);
    font-size: 0.74rem;
    letter-spacing: 0.1em;
    text-align: left;
    padding: 0.7rem 0.9rem;
    border-bottom: 1px solid var(--c-grid);
    text-transform: uppercase;
    font-weight: 500;
}

.spec-table tbody td {
    padding: 0.7rem 0.9rem;
    border-bottom: 1px dashed var(--c-grid);
    color: var(--c-text);
    vertical-align: middle;
}

.spec-table tbody tr:last-child td {
    border-bottom: 0;
}

.spec-table tbody tr:hover td {
    background: rgba(52, 152, 219, 0.05);
}

.spec-table code {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--c-blue);
}

/* ---------- Timeline ---------- */
.timeline {
    position: relative;
    padding: 2rem 1rem 1rem;
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    background: var(--c-panel);
    overflow-x: auto;
}

.timeline-axis {
    position: absolute;
    left: 1rem;
    right: 1rem;
    top: 50%;
    height: 1px;
    background: var(--c-conn);
    background-image: repeating-linear-gradient(
        90deg,
        var(--c-conn) 0,
        var(--c-conn) 4px,
        transparent 4px,
        transparent 6px
    );
    background-color: transparent;
}

.timeline-events {
    position: relative;
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: space-between;
    gap: 0.5rem;
    min-width: 720px;
}

.event {
    position: relative;
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.4rem;
    cursor: pointer;
    padding: 0.5rem 0.25rem;
    border-radius: var(--rad);
    transition: background 200ms ease;
    min-width: 70px;
}

.event:hover {
    background: rgba(52, 152, 219, 0.05);
}

.event-id {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.04em;
}

.event-dot {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    border: 1px solid currentColor;
    background: rgba(10, 22, 40, 0.8);
    position: relative;
    z-index: 2;
    transition: transform 200ms ease, background 200ms ease;
}

.event[data-state="committed"] .event-dot {
    color: var(--c-green);
    background: rgba(46, 204, 113, 0.25);
}

.event[data-state="pending"] .event-dot {
    color: var(--c-blue);
    background: rgba(52, 152, 219, 0.25);
}

.event[data-state="failed"] .event-dot {
    color: var(--c-red);
    background: rgba(231, 76, 60, 0.25);
}

.event.is-selected .event-dot,
.event.is-related .event-dot {
    transform: scale(1.45);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.15);
}

.event.is-selected {
    background: var(--c-blue-glow);
}

.event-label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.04em;
    text-align: center;
}

.timeline-detail {
    margin-top: 1rem;
    padding: 0.65rem 0.9rem;
    border: 1px dashed var(--c-grid);
    border-radius: var(--rad);
    background: rgba(10, 22, 40, 0.4);
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--c-text);
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.5rem;
    letter-spacing: 0.04em;
}

.td-label {
    color: var(--c-blue);
    letter-spacing: 0.12em;
}

.td-sep {
    color: var(--c-text-dim);
}

.td-state {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
}

/* ---------- Failure grid ---------- */
.failure-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1rem;
}

.fail {
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    padding: 1rem 1rem 0.9rem;
    background: var(--c-panel);
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    transition: border-color 220ms ease;
}

.fail:hover {
    border-color: var(--c-blue);
}

.fail-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--c-text-dim);
    letter-spacing: 0.08em;
}

.fail-id {
    color: var(--c-blue);
}

.fail-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin: 0;
    color: var(--c-text);
}

.fail-body {
    margin: 0;
    font-size: 0.85rem;
    color: var(--c-text-dim);
}

.fail-body code {
    font-family: var(--font-mono);
    color: var(--c-blue);
    font-size: 0.8rem;
}

/* ---------- References ---------- */
.ref-list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.ref {
    display: grid;
    grid-template-columns: 40px 1fr;
    gap: 0.75rem;
    padding: 0.7rem 0.9rem;
    border: 1px solid var(--c-grid);
    border-radius: var(--rad);
    background: var(--c-panel);
    font-size: 0.88rem;
    color: var(--c-text);
}

.ref-key {
    font-family: var(--font-mono);
    color: var(--c-blue);
    font-size: 0.78rem;
    letter-spacing: 0.05em;
}

.ref-body em {
    color: var(--c-text);
    font-style: italic;
}

.ref-body {
    color: var(--c-text-dim);
}

/* ---------- Footer ---------- */
.site-footer {
    margin-top: 4rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--c-grid);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1.5rem;
    font-family: var(--font-mono);
    font-size: 0.78rem;
}

.foot-col {
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
}

.foot-title {
    color: var(--c-blue);
    letter-spacing: 0.1em;
    font-size: 0.7rem;
    text-transform: uppercase;
}

.foot-body {
    color: var(--c-text-dim);
}

.foot-body .dot {
    margin-right: 0.3rem;
}

/* ---------- Dot indicators ---------- */
.dot {
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: currentColor;
    box-shadow: 0 0 0 1px rgba(10, 22, 40, 0.5);
    vertical-align: middle;
}

.dot-green {
    color: var(--c-green);
    background: var(--c-green);
}

.dot-blue {
    color: var(--c-blue);
    background: var(--c-blue);
}

.dot-red {
    color: var(--c-red);
    background: var(--c-red);
}

/* ---------- Diagram SVG line styling ---------- */
.diagram-svg .conn {
    stroke: var(--c-conn);
    stroke-width: 1;
    fill: none;
}

.diagram-svg .conn-dashed {
    stroke-dasharray: 4 2;
}

.diagram-svg .conn-blue {
    stroke: var(--c-blue);
    stroke-dasharray: 6 3;
    opacity: 0.65;
}

/* ---------- Responsive ---------- */
@media (max-width: 960px) {
    .layout {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: relative;
        height: auto;
        max-height: none;
        border-right: 0;
        border-bottom: 1px solid var(--c-grid);
        padding: 1.25rem 1.5rem;
    }

    .sidebar-legend {
        flex-direction: row;
        flex-wrap: wrap;
        gap: 0.8rem 1rem;
    }

    .legend-title {
        flex-basis: 100%;
        margin-bottom: 0;
    }

    .content {
        padding: 2rem 1.25rem 3rem;
    }

    .section-header {
        grid-template-columns: 40px 1fr;
        gap: 0.75rem;
    }

    .diagram-svg {
        height: 420px;
    }
}

@media (max-width: 640px) {
    .site-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
        padding: 1rem 1.25rem;
    }

    .meta-nav {
        flex-wrap: wrap;
        gap: 0.75rem;
    }

    .diagram-svg {
        height: 720px;
    }
}