:root {
  --bg: #f6f7f9; --panel: #ffffff; --ink: #14181f; --muted: #5b6573; --line: #d9dee6;
  --accent: #2563eb; --accent-ink: #ffffff; --edge: #9aa5b5; --node-bg: #ffffff; --node-ink: #14181f;
  --ks: 62%; --kl: 42%; --shadow: 0 1px 2px rgba(20,24,31,.06), 0 4px 14px rgba(20,24,31,.06);
  --code-bg: #f0f2f6; --focus: #2563eb;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1218; --panel: #161b23; --ink: #e8ecf2; --muted: #98a3b3; --line: #2a323e;
    --accent: #6ea0ff; --accent-ink: #0b1220; --edge: #5b6778; --node-bg: #1b222c; --node-ink: #e8ecf2;
    --ks: 70%; --kl: 62%; --shadow: none; --code-bg: #10151c; --focus: #8db3ff;
  }
}
:root[data-theme="dark"] {
  --bg: #0e1218; --panel: #161b23; --ink: #e8ecf2; --muted: #98a3b3; --line: #2a323e;
  --accent: #6ea0ff; --accent-ink: #0b1220; --edge: #5b6778; --node-bg: #1b222c; --node-ink: #e8ecf2;
  --ks: 70%; --kl: 62%; --shadow: none; --code-bg: #10151c; --focus: #8db3ff;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { margin: 0; height: 100%; }
body { background: var(--bg); color: var(--ink); font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
h1, h2, h3 { margin: 0; line-height: 1.25; }
code, pre { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .88em; }
code { background: var(--code-bg); padding: .05em .35em; border-radius: 4px; }
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* no-JS fallback */
.static { display: none; max-width: 860px; margin: 0 auto; padding: 24px 16px; }
html:not(.js) .static { display: block; }
html.js .static { display: none; }

.app { display: flex; flex-direction: column; height: 100vh; height: 100dvh; }
.app[hidden] { display: none; }
.topbar { display: flex; gap: 16px; align-items: center; justify-content: space-between; padding: 12px 20px; background: var(--panel); border-bottom: 1px solid var(--line); }
.title h1 { font-size: 18px; }
.title p { margin: 2px 0 0; color: var(--muted); font-size: 13px; max-width: 70ch; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.top-actions { display: flex; gap: 10px; align-items: center; flex-shrink: 0; }

.layout { flex: 1; min-height: 0; display: grid; grid-template-columns: minmax(0, 1fr) 380px; gap: 14px; padding: 14px; }
.stage { display: flex; flex-direction: column; min-height: 0; gap: 10px; }
.canvas { position: relative; flex: 1; min-height: 240px; background: var(--panel); border: 1px solid var(--line); border-radius: 12px; overflow: hidden; box-shadow: var(--shadow); }
#diagram { width: 100%; height: 100%; display: block; touch-action: none; cursor: grab; }
#diagram.panning { cursor: grabbing; }
.search { position: absolute; left: 10px; top: 10px; display: flex; align-items: center; gap: 8px; z-index: 1; }
.search input { font: inherit; font-size: 13px; width: 220px; max-width: 46vw; padding: 6px 10px; color: var(--ink); background: color-mix(in srgb, var(--panel) 92%, transparent); border: 1px solid var(--line); border-radius: 8px; }
.search input:focus { outline: 2px solid var(--focus); border-color: transparent; }
.zoom { position: absolute; right: 10px; top: 10px; display: flex; flex-direction: column; gap: 6px; }
.legend { position: absolute; left: 10px; bottom: 10px; display: flex; flex-wrap: wrap; gap: 6px 12px; font-size: 12px; color: var(--muted); background: color-mix(in srgb, var(--panel) 88%, transparent); padding: 6px 10px; border-radius: 8px; max-width: calc(100% - 70px); }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: 5px; vertical-align: -1px; background: var(--kc); }

.side { display: flex; flex-direction: column; gap: 14px; min-height: 0; overflow: auto; }
.card { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; box-shadow: var(--shadow); }
.card h2 { font-size: 15px; margin-bottom: 6px; }
.caption { margin: 0; font-size: 15px; line-height: 1.6; }
.muted { color: var(--muted); margin: 0; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 10px; }
.chip { font: inherit; font-size: 12px; padding: 3px 9px; border-radius: 99px; border: 1px solid var(--line); background: var(--code-bg); color: var(--ink); cursor: pointer; }
.chip:hover { border-color: var(--accent); }
#detail-body h3 { font-size: 16px; }
.pill { display: inline-block; font-size: 11px; text-transform: uppercase; letter-spacing: .04em; padding: 1px 8px; border-radius: 99px; color: #fff; background: var(--kc); margin-right: 6px; }
.kv { margin: 10px 0 0; font-size: 13px; color: var(--muted); }
.kv b { color: var(--ink); font-weight: 600; }
.src { border-top: 1px solid var(--line); padding: 10px 0 2px; margin-top: 10px; }
.src-row { display: flex; gap: 8px; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.src-row code { word-break: break-all; }
.src pre { margin: 8px 0 0; padding: 10px; background: var(--code-bg); border-radius: 8px; overflow: auto; max-height: 240px; white-space: pre; tab-size: 2; }
.src .note { font-size: 12px; color: var(--muted); margin: 4px 0 0; }
.links { margin: 10px 0 0; padding: 0; list-style: none; display: flex; flex-wrap: wrap; gap: 6px; }

.btn { font: inherit; font-size: 14px; border: 1px solid var(--line); background: var(--panel); color: var(--ink); border-radius: 8px; padding: 6px 12px; cursor: pointer; text-decoration: none; display: inline-flex; align-items: center; gap: 6px; }
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); font-weight: 600; min-width: 92px; justify-content: center; }
.btn.icon { padding: 6px 10px; min-width: 36px; justify-content: center; }
.zoom .btn.small { font-size: 11px; padding: 6px 4px; letter-spacing: .02em; }
.btn.small { padding: 3px 10px; font-size: 13px; }
.btn.ghost { background: transparent; }
.btn:disabled { opacity: .45; cursor: not-allowed; }

.player { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 10px 14px 12px; box-shadow: var(--shadow); }
.progress { position: relative; height: 8px; border-radius: 99px; background: var(--code-bg); margin: 4px 0 12px; cursor: pointer; }
.progress .bar { height: 100%; width: 0; border-radius: 99px; background: var(--accent); transition: width .3s ease; }
.progress .dots { position: absolute; inset: 0; display: flex; }
.progress .dots button { flex: 1; background: none; border: 0; padding: 0; cursor: pointer; height: 16px; margin-top: -4px; }
.progress .dots button:hover, .progress .dots button:focus-visible { background: color-mix(in srgb, var(--accent) 20%, transparent); }
.controls { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 10px; }
.controls.narr { margin-top: 10px; padding-top: 10px; border-top: 1px dashed var(--line); font-size: 13px; }
.step-count { color: var(--muted); font-size: 13px; min-width: 84px; }
.field { display: inline-flex; flex-direction: column; gap: 2px; font-size: 12px; color: var(--muted); }
.field.inline { flex-direction: row; align-items: center; gap: 6px; }
select { font: inherit; font-size: 13px; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: 8px; padding: 5px 8px; max-width: 220px; }
.check { display: inline-flex; gap: 6px; align-items: center; cursor: pointer; }
.hint { color: var(--muted); font-size: 12px; }

/* ---- SVG diagram ---- */
.edge path.line { fill: none; stroke: var(--edge); stroke-width: 1.5; transition: stroke .25s, stroke-width .25s; pointer-events: none; }
.edge path.hit { fill: none; stroke: transparent; stroke-width: 14; }
.edge { transition: opacity .25s; }
.edge text { font-size: 11px; fill: var(--muted); paint-order: stroke; stroke: var(--panel); stroke-width: 4px; opacity: 0; transition: opacity .2s; pointer-events: none; }
.edge:hover text, .edge.active text, .edge.selected text { opacity: 1; }
.edge.visited path.line { stroke: color-mix(in srgb, var(--accent) 55%, var(--edge)); }
.edge.selected path.line { stroke: var(--accent); }
.edge.active path.line { stroke: var(--accent); stroke-width: 3; stroke-dasharray: 8 6; animation: flow 0.9s linear infinite; }
.edge.k-http:not(.active):not(.selected) path.line { stroke: color-mix(in srgb, var(--accent) 70%, var(--edge)); stroke-dasharray: 2 5; stroke-linecap: round; }
.legend .http-key { display: inline-block; width: 18px; height: 0; border-top: 2px dotted var(--accent); background: none; border-radius: 0; vertical-align: middle; }
.edge.dim { opacity: .28; }
@keyframes flow { to { stroke-dashoffset: -14; } }
.arrow-head { fill: var(--edge); }
.arrow-head.a { fill: var(--accent); }
.arrow-head.v { fill: color-mix(in srgb, var(--accent) 55%, var(--edge)); }
.lane { fill: color-mix(in srgb, var(--kc) 7%, transparent); stroke: color-mix(in srgb, var(--kc) 35%, transparent); stroke-dasharray: 5 5; }
.lane-label { font-size: 11.5px; font-weight: 700; letter-spacing: .07em; fill: var(--muted); }
.node { cursor: pointer; transition: opacity .25s; }
.node rect.box { fill: var(--node-bg); stroke: var(--kc); stroke-width: 1.5; transition: stroke-width .2s, filter .2s; }
.node rect.bar { fill: var(--kc); }
.node text { fill: var(--node-ink); pointer-events: none; }
.node .lbl { font-size: 14px; font-weight: 600; }
.node .sub { font-size: 11.5px; fill: var(--muted); }
.node:hover rect.box, .node:focus-visible rect.box { stroke-width: 2.5; }
.node.visited rect.box { fill: color-mix(in srgb, var(--kc) 10%, var(--node-bg)); }
.node.active rect.box { stroke-width: 3.5; fill: color-mix(in srgb, var(--kc) 18%, var(--node-bg)); filter: drop-shadow(0 0 7px color-mix(in srgb, var(--kc) 60%, transparent)); }
.node.selected rect.box { stroke-width: 3.5; stroke-dasharray: 0; }
.node.selected::after { content: ""; }
.node.dim { opacity: .35; }
.node.s-miss { opacity: .15 !important; }
.edge.s-miss { opacity: .08 !important; }
.node.s-hit rect.box { stroke-width: 3.5; filter: drop-shadow(0 0 6px color-mix(in srgb, var(--kc) 55%, transparent)); }
.node:focus { outline: none; }
.node:focus-visible rect.box { stroke: var(--focus); }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
  .edge.active path.line { stroke-dasharray: none; stroke-width: 4; }
}

/* ---- tablet / phone ---- */
@media (max-width: 900px) {
  .app { height: auto; min-height: 100vh; }
  .layout { grid-template-columns: 1fr; padding: 10px 16px 16px; }
  .canvas { height: 56vh; min-height: 280px; flex: none; }
  .topbar { flex-direction: column; align-items: stretch; padding: 12px 16px; }
  .top-actions { justify-content: space-between; }
  .stage, .side { display: contents; }
  .canvas { order: 1; }
  #narration { order: 2; }
  .player { order: 3; }
  #detail { order: 4; }
  .legend { display: none; }
  .btn { padding: 9px 12px; }
  .controls { justify-content: space-between; }
  .step-count { flex-basis: 100%; order: 9; }
}

/* architecture diff: components and relationships marked added / removed / changed */
:root { --d-added: #2ea043; --d-removed: #f85149; --d-changed: #d29922; }
.node.d-added rect.box { stroke: var(--d-added); stroke-width: 3; }
.node.d-changed rect.box { stroke: var(--d-changed); stroke-width: 3; }
.node.d-removed rect.box { stroke: var(--d-removed); stroke-width: 2.5; stroke-dasharray: 6 4; }
.node.d-removed .lbl { text-decoration: line-through; }
.node.d-removed rect.bar { fill: var(--d-removed); }
.edge.d-added:not(.active):not(.selected) path.line { stroke: var(--d-added); stroke-width: 2.5; stroke-dasharray: none; }
.edge.d-changed:not(.active):not(.selected) path.line { stroke: var(--d-changed); stroke-width: 2.5; stroke-dasharray: none; }
.edge.d-removed:not(.active):not(.selected) path.line { stroke: var(--d-removed); stroke-dasharray: 6 4; }
.legend .diff-key { background: none; border: 2px solid var(--kc); width: 10px; height: 10px; box-sizing: border-box; }
.legend .diff-key.d-added { --kc: var(--d-added); }
.legend .diff-key.d-removed { --kc: var(--d-removed); border-style: dashed; }
.legend .diff-key.d-changed { --kc: var(--d-changed); }
.diff-note b { color: var(--kc); }
.diff-note.d-added { --kc: var(--d-added); }
.diff-note.d-removed { --kc: var(--d-removed); }
.diff-note.d-changed { --kc: var(--d-changed); }

.ai-tag { display: inline-block; margin: 2px 0 6px; font-size: 11.5px; font-weight: 700; letter-spacing: .04em; padding: 2px 9px; border-radius: 99px; color: var(--accent); border: 1px solid color-mix(in srgb, var(--accent) 45%, transparent); background: color-mix(in srgb, var(--accent) 10%, transparent); }

/* accessibility */
.sr { position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0; overflow: hidden; clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap; border: 0; }
.skip { position: absolute; left: 8px; top: -48px; z-index: 50; padding: 8px 14px; border-radius: 8px; background: var(--accent); color: var(--accent-ink); font-weight: 600; text-decoration: none; transition: top .12s; }
.skip:focus { top: 8px; }
.node:focus-visible rect.box { stroke-width: 4; }
@media (forced-colors: active) {
  .node rect.box { stroke: CanvasText; fill: Canvas; }
  .node text { fill: CanvasText; }
  .node.selected rect.box, .node:focus-visible rect.box, .node.active rect.box { stroke: Highlight; stroke-width: 4; }
  .edge path.line { stroke: GrayText; }
  .edge.active path.line, .edge.selected path.line { stroke: Highlight; }
}

/* collapsible swimlanes */
.lane-hidden { display: none; }
.lane-head { cursor: pointer; outline: none; }
.lane-head .lane-hit { fill: transparent; transition: fill .15s; }
.lane-head:hover .lane-hit, .lane-head:focus-visible .lane-hit { fill: color-mix(in srgb, var(--kc) 16%, transparent); }
.lane-head:focus-visible .lane-hit { stroke: var(--focus); stroke-width: 2; }
.lane-caret { font-size: 12px; fill: var(--muted); pointer-events: none; }
.lane-head .lane-label { pointer-events: none; }
.lane-group.collapsed .lane { stroke-dasharray: 2 4; }
.lane-chip rect.box { fill: var(--node-bg); stroke: var(--kc); stroke-width: 1.8; }
.lane-chip rect.stack { fill: var(--node-bg); stroke: color-mix(in srgb, var(--kc) 55%, var(--line)); stroke-width: 1.2; }
.lane-chip rect.bar { fill: var(--kc); }
.lane-chip text { fill: var(--node-ink); pointer-events: none; }
.lane-chip .lbl { font-size: 14px; font-weight: 600; }
.lane-chip .sub { font-size: 11.5px; fill: var(--muted); }
.lane-chip.visited rect.box { fill: color-mix(in srgb, var(--kc) 10%, var(--node-bg)); }
.lane-chip.active rect.box { stroke-width: 3.5; fill: color-mix(in srgb, var(--kc) 18%, var(--node-bg)); filter: drop-shadow(0 0 7px color-mix(in srgb, var(--kc) 60%, transparent)); }
.lane-chip.dim { opacity: .35; }
.lane-chip:hover rect.box, .lane-chip:focus-visible rect.box { stroke-width: 2.8; }
.lane-chip:focus { outline: none; }
.lane-chip:focus-visible rect.box { stroke: var(--focus); stroke-width: 4; }
@media (forced-colors: active) {
  .lane-chip rect.box, .lane-chip rect.stack { stroke: CanvasText; fill: Canvas; }
  .lane-chip.active rect.box, .lane-chip:focus-visible rect.box { stroke: Highlight; stroke-width: 4; }
}

/* ---------- keyboard shortcuts dialog ---------- */
.dlg { width: min(420px, calc(100vw - 32px)); max-height: calc(100vh - 32px); overflow: auto; padding: 20px 22px; border: 1px solid var(--line); border-radius: 14px; background: var(--panel); color: var(--ink); box-shadow: var(--shadow); }
.dlg::backdrop { background: rgba(8, 12, 24, .5); }
.dlg h2 { font-size: 18px; margin: 0 0 14px; }
#shortcuts-list { display: grid; grid-template-columns: auto 1fr; gap: 8px 16px; margin: 0 0 16px; align-items: center; }
#shortcuts-list dt { display: flex; gap: 4px; align-items: center; font-weight: normal; }
#shortcuts-list dd { margin: 0; font-size: 13.5px; color: var(--muted); }
#shortcuts-list kbd { font: inherit; font-size: 12px; padding: 2px 7px; border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 6px; background: var(--bg); min-width: 1.6em; text-align: center; }