.collaboration-section {
    --network-ink: #17202a;
    --network-muted: #5e6a75;
    --network-line: #dce2e7;
    --network-accent: #0b6e75;
    margin: 42px 0 48px;
    padding: clamp(22px, 4vw, 38px);
    color: var(--network-ink);
    background: linear-gradient(145deg, #f7fafb 0%, #eef6f6 100%);
    border: 1px solid #dce8e8;
    border-radius: 18px;
    box-shadow: 0 18px 45px rgba(19, 50, 55, 0.08);
}

.collaboration-heading {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 28px;
    margin-bottom: 22px;
}

.collaboration-heading h2 {
    margin: 2px 0 6px;
    font-size: clamp(1.7rem, 3vw, 2.35rem);
    letter-spacing: -0.035em;
    color: var(--network-ink);
}

.collaboration-heading p:not(.eyebrow) {
    max-width: 680px;
    margin: 0;
    color: var(--network-muted);
}

.eyebrow,
.detail-kicker {
    margin: 0;
    color: var(--network-accent);
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.collaboration-stats {
    display: flex;
    flex-shrink: 0;
    gap: 8px;
}

.collaboration-stats span {
    min-width: 92px;
    padding: 10px 12px;
    color: var(--network-muted);
    background: rgba(255, 255, 255, 0.78);
    border: 1px solid var(--network-line);
    border-radius: 10px;
    font-size: 0.78rem;
    line-height: 1.25;
    text-align: center;
}

.collaboration-stats strong {
    display: block;
    color: var(--network-ink);
    font-size: 1.25rem;
}

.topic-filters {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 18px;
}

.topic-filter {
    padding: 8px 13px;
    border: 1px solid var(--topic-color, #8a969e);
    border-radius: 999px;
    color: var(--network-ink);
    background: #fff;
    font: inherit;
    font-size: 0.86rem;
    cursor: pointer;
    transition: transform 160ms ease, color 160ms ease, background 160ms ease;
}

.topic-filter:hover { transform: translateY(-1px); }
.topic-filter[aria-pressed="true"] {
    color: #fff;
    background: var(--topic-color, var(--network-accent));
}
.topic-filter:focus-visible,
.graph-node:focus-visible {
    outline: 3px solid rgba(11, 110, 117, 0.32);
    outline-offset: 3px;
}

.collaboration-layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 245px;
    gap: 18px;
}

.network-panel,
.collaborator-detail {
    background: rgba(255, 255, 255, 0.82);
    border: 1px solid var(--network-line);
    border-radius: 14px;
}

.network-panel { padding: 8px; overflow-x: auto; }
#collaboration-graph {
    display: block;
    width: 100%;
    min-width: 900px;
    min-height: 620px;
}

.topic-region {
    fill: var(--region-color);
    fill-opacity: 0.055;
    stroke: var(--region-color);
    stroke-width: 2;
    stroke-dasharray: 7 9;
    transition: opacity 160ms ease;
}
.topic-region-label {
    fill: var(--region-color);
    font: 700 18px Arial, sans-serif;
    letter-spacing: 0.02em;
    paint-order: stroke;
    stroke: #fff;
    stroke-width: 5px;
}
.topic-region.is-muted,
.topic-region-label.is-muted { opacity: 0.08; }

.coauthor-edge {
    stroke: #53636c;
    stroke-linecap: round;
    opacity: 0.16;
    transition: opacity 160ms ease, stroke 160ms ease;
}
.coauthor-edge.is-muted { opacity: 0.018; }
.coauthor-edge.is-selected {
    stroke: #17202a;
    opacity: 0.72;
}

.coauthor-node { cursor: pointer; transition: opacity 160ms ease; }
.coauthor-node circle {
    fill: var(--node-color);
    stroke: #fff;
    stroke-width: 3;
    filter: drop-shadow(0 3px 5px rgba(16, 39, 43, 0.22));
    transition: transform 160ms ease, stroke-width 160ms ease;
    transform-box: fill-box;
    transform-origin: center;
}
.coauthor-node.cross-topic circle { stroke: #17202a; stroke-width: 4; }
.coauthor-node.central-author circle { stroke-width: 5; }
.coauthor-node:hover circle,
.coauthor-node:focus circle { transform: scale(1.16); }
.coauthor-node.is-muted { opacity: 0.12; }
.coauthor-node.is-selected circle { stroke: #f1b82d; stroke-width: 6; }
.coauthor-node text {
    fill: #243139;
    font: 600 11px Arial, sans-serif;
    paint-order: stroke;
    stroke: #fff;
    stroke-width: 3.5px;
    stroke-linejoin: round;
}
.coauthor-node.central-author text { font-size: 14px; font-weight: 700; }
.coauthor-node:focus-visible { outline: none; }
.coauthor-node:focus-visible circle { stroke: #f1b82d; stroke-width: 6; }

.reset-network {
    margin-top: 14px;
    padding: 9px 12px;
    color: #fff;
    background: var(--network-accent);
    border: 0;
    border-radius: 8px;
    font: 600 0.84rem Arial, sans-serif;
    cursor: pointer;
}
.reset-network:hover { background: #084f55; }
.reset-network:focus-visible { outline: 3px solid rgba(11, 110, 117, 0.3); outline-offset: 2px; }

.subgraph-grid {
    display: grid !important;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 12px;
}

.topic-subgraph {
    min-width: 0;
    overflow: hidden;
    background: color-mix(in srgb, var(--subgraph-color) 5%, white);
    border: 1px solid color-mix(in srgb, var(--subgraph-color) 28%, white);
    border-radius: 12px;
}

.topic-subgraph[hidden] { display: none; }
.topic-subgraph:only-of-type { grid-column: 1 / -1; }
.subgraph-heading {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    gap: 12px;
    padding: 13px 15px 0;
}
.subgraph-heading h3 {
    margin: 0;
    color: var(--subgraph-color);
    font-size: 1rem;
}
.subgraph-heading span {
    color: var(--network-muted);
    font-size: 0.76rem;
    white-space: nowrap;
}
.topic-subgraph svg { display: block; width: 100%; height: auto; }
.subgraph-edge {
    stroke: var(--subgraph-color);
    opacity: 0.28;
    stroke-linecap: round;
}
.subgraph-hub circle {
    fill: var(--subgraph-color);
    stroke: #fff;
    stroke-width: 4;
    filter: drop-shadow(0 5px 8px rgba(16, 39, 43, 0.2));
}
.subgraph-hub text {
    fill: #fff;
    font: 700 12px Arial, sans-serif;
}
.subgraph-person { cursor: pointer; }
.subgraph-person circle {
    fill: var(--subgraph-color);
    stroke: #fff;
    stroke-width: 3;
    transition: transform 160ms ease;
    transform-box: fill-box;
    transform-origin: center;
}
.subgraph-person.is-bridge circle {
    stroke: #17202a;
    stroke-width: 4;
}
.subgraph-person:hover circle,
.subgraph-person:focus circle { transform: scale(1.16); }
.subgraph-person:focus-visible { outline: none; }
.subgraph-person:focus-visible circle { stroke: #17202a; stroke-width: 5; }
.subgraph-person text {
    fill: #25323a;
    font: 600 10.5px Arial, sans-serif;
    paint-order: stroke;
    stroke: #fff;
    stroke-width: 3px;
    stroke-linejoin: round;
}

.graph-edge {
    stroke: var(--edge-color);
    stroke-linecap: round;
    opacity: 0.35;
    transition: opacity 160ms ease;
}
.graph-edge.is-muted { opacity: 0.05; }
.topic-spine {
    stroke-width: 3;
    stroke-dasharray: 7 8;
    opacity: 0.3;
}
.collaboration-edge { opacity: 0.46; }

.cluster-halo {
    fill: var(--node-color);
    opacity: 0.055;
    stroke: var(--node-color);
    stroke-width: 1.5;
    stroke-dasharray: 5 8;
    transition: opacity 160ms ease;
}
.cluster-halo.is-muted { opacity: 0.012; }

.graph-node { cursor: pointer; }
.graph-node circle {
    fill: var(--node-color);
    stroke: #fff;
    stroke-width: 3;
    filter: drop-shadow(0 4px 6px rgba(16, 39, 43, 0.16));
    transition: transform 160ms ease, opacity 160ms ease;
    transform-box: fill-box;
    transform-origin: center;
}
.graph-node:hover circle,
.graph-node:focus circle { transform: scale(1.08); }
.graph-node.is-muted { opacity: 0.16; }
.graph-node.is-selected circle { stroke: #17202a; stroke-width: 5; }
.topic-node circle {
    stroke-width: 5;
    filter: drop-shadow(0 7px 12px rgba(16, 39, 43, 0.2));
}
.topic-node.is-active-topic circle {
    stroke: #17202a;
    stroke-width: 6;
}
.graph-label {
    fill: #243139;
    font-family: Arial, sans-serif;
    font-size: 14px;
    font-weight: 600;
    paint-order: stroke;
    stroke: #fff;
    stroke-width: 4px;
    stroke-linejoin: round;
}
.graph-label.is-central { font-size: 16px; font-weight: 700; }
.topic-label {
    fill: #fff;
    font-size: 13px;
    font-weight: 700;
    stroke: none;
}
.graph-hint {
    margin: 4px 10px 8px;
    color: var(--network-muted);
    font-size: 0.8rem;
}

.collaborator-detail {
    align-self: stretch;
    padding: 22px;
}
.collaborator-detail h3 { margin: 5px 0 8px; font-size: 1.22rem; }
.collaborator-detail p { color: var(--network-muted); }
.bridge-note {
    padding: 10px 12px;
    background: #eef6f6;
    border-left: 3px solid var(--network-accent);
    border-radius: 0 7px 7px 0;
    font-size: 0.86rem;
}
.detail-topics { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 16px; }
.detail-topic {
    padding: 5px 8px;
    border-radius: 7px;
    color: #fff;
    font-size: 0.76rem;
}
.graph-fallback { padding: 14px; background: #fff; border-radius: 10px; }

@media (max-width: 820px) {
    .collaboration-heading { align-items: flex-start; flex-direction: column; }
    .collaboration-layout { grid-template-columns: 1fr; }
    .collaborator-detail { min-height: 120px; }
    .subgraph-grid { grid-template-columns: 1fr; }
}

@media (max-width: 560px) {
    .collaboration-section { margin-right: -8px; margin-left: -8px; padding: 18px 12px; }
    .collaboration-stats { width: 100%; }
    .collaboration-stats span { flex: 1; }
    #collaboration-graph { min-height: 620px; }
    .graph-label { font-size: 12px; }
}

@media (prefers-reduced-motion: reduce) {
    .topic-filter,
    .graph-node circle { transition: none; }
}