.trace-page {
  min-height: 100vh;
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

.trace-page * { box-sizing: border-box; }
.trace-page a { color: var(--accent); }
.trace-page button, .trace-page select { font: inherit; }
.trace-page button:focus-visible, .trace-page a:focus-visible, .trace-page input:focus-visible, .trace-page select:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.trace-skip {
  position: absolute;
  left: 1rem;
  top: -5rem;
  padding: .65rem 1rem;
  background: var(--panel-strong);
  z-index: 20;
}
.trace-skip:focus { top: 1rem; }

.trace-shell { width: min(1480px, calc(100% - 44px)); margin: 0 auto; padding: 28px 0 48px; }
.trace-header { display: flex; justify-content: space-between; align-items: flex-start; gap: 24px; margin-bottom: 24px; }
.trace-top-links { display: flex; gap: 20px; flex-wrap: wrap; margin-bottom: 28px; font-size: .9rem; }
.trace-top-links a { text-decoration: none; font-weight: 650; }
.trace-top-links a:hover, .trace-footer a:hover { text-decoration: underline; }
.trace-eyebrow { margin: 0 0 7px; color: var(--accent); font-size: .76rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; }
.trace-header h1 { margin: 0; font-size: clamp(2.4rem, 5vw, 4.9rem); letter-spacing: -.055em; line-height: 1.02; }
.trace-lede { max-width: 67ch; margin: 16px 0 0; color: var(--copy); font-size: clamp(1rem, 1.7vw, 1.14rem); line-height: 1.58; }
.trace-theme { display: grid; gap: 6px; min-width: 140px; color: var(--muted); font-size: .78rem; font-weight: 700; }
.trace-theme select { width: 100%; padding: 8px 10px; border: 1px solid var(--line); border-radius: 9px; background: var(--panel-strong); color: var(--ink); }

.trace-notice { display: flex; gap: 14px; align-items: baseline; padding: 15px 18px; border: 1px solid color-mix(in srgb, var(--amber) 40%, var(--line)); border-left: 5px solid var(--amber); border-radius: 12px; background: var(--panel); line-height: 1.5; font-size: .9rem; }
.trace-notice strong { white-space: nowrap; color: var(--ink); }
.trace-notice span { color: var(--copy); }
.trace-example { display: grid; grid-template-columns: 2fr 1fr .8fr .8fr .8fr; gap: 1px; margin: 18px 0 24px; overflow: hidden; border: 1px solid var(--line); border-radius: 12px; background: var(--line); }
.trace-example > div { display: grid; gap: 4px; padding: 14px 17px; background: var(--panel-strong); }
.trace-example span { color: var(--muted); font-size: .72rem; font-weight: 750; letter-spacing: .06em; text-transform: uppercase; }
.trace-example strong { font-size: .93rem; }

.trace-workspace { display: grid; grid-template-columns: 252px minmax(0, 1fr); align-items: start; gap: 20px; }
.trace-rail { position: sticky; top: 18px; max-height: calc(100vh - 36px); overflow: auto; border: 1px solid var(--line); border-radius: 16px; background: var(--panel); box-shadow: var(--shadow-soft); }
.trace-rail-header { display: flex; justify-content: space-between; padding: 18px 18px 12px; color: var(--muted); font-size: .75rem; font-weight: 800; letter-spacing: .1em; text-transform: uppercase; }
.trace-rail nav { display: grid; padding: 0 9px 12px; }
.trace-phase-label { margin: 16px 9px 7px; color: var(--muted); font-size: .68rem; font-weight: 850; letter-spacing: .13em; text-transform: uppercase; }
.trace-stage-link { display: flex; align-items: center; gap: 10px; width: 100%; padding: 10px 11px; border: 0; border-radius: 9px; background: transparent; color: var(--copy); text-align: left; cursor: pointer; font-size: .85rem; line-height: 1.3; }
.trace-stage-link:hover { background: var(--surface-chip); color: var(--ink); }
.trace-stage-link[aria-current="step"] { background: color-mix(in srgb, var(--accent) 12%, var(--panel-strong)); color: var(--ink); font-weight: 750; }
.trace-stage-number { flex: none; width: 25px; height: 25px; display: grid; place-items: center; border-radius: 7px; background: var(--panel-strong); border: 1px solid var(--line); color: var(--muted); font-size: .73rem; font-variant-numeric: tabular-nums; }
.trace-stage-link[aria-current="step"] .trace-stage-number { color: var(--accent); border-color: var(--accent); }

.trace-main { min-width: 0; }
.trace-progress { height: 5px; margin: 0 2px 12px; border-radius: 5px; background: var(--line); overflow: hidden; }
.trace-progress span { display: block; width: 6.25%; height: 100%; background: var(--accent); transition: width .2s ease; }
.trace-stage, .trace-controls { border: 1px solid var(--line); border-radius: 17px; background: var(--panel); box-shadow: var(--shadow-soft); }
.trace-stage { padding: clamp(18px, 3vw, 32px); }
.trace-stage-head { display: flex; justify-content: space-between; gap: 18px; align-items: start; }
.trace-stage-head h2 { margin: 0; font-size: clamp(1.55rem, 2.5vw, 2.3rem); letter-spacing: -.035em; }
.trace-stage-position { flex: none; padding: 6px 10px; border: 1px solid var(--line); border-radius: 20px; color: var(--muted); font-size: .75rem; font-variant-numeric: tabular-nums; }
.trace-takeaway { max-width: 70ch; margin: 17px 0 26px; padding-left: 15px; border-left: 3px solid var(--accent); color: var(--copy-strong); font-size: 1.03rem; line-height: 1.55; }
.trace-tensor-flow { display: grid; grid-template-columns: minmax(0, 1fr) 36px minmax(0, 1fr); align-items: stretch; gap: 8px; }
.trace-tensor-card { min-width: 0; padding: 19px; border: 1px solid var(--line); border-radius: 14px; background: var(--panel-strong); }
.trace-card-kicker { color: var(--muted); font-size: .72rem; font-weight: 850; letter-spacing: .1em; text-transform: uppercase; }
.trace-card-header h3 { min-height: 2.4em; margin: 7px 0 10px; font-size: 1rem; line-height: 1.25; }
.trace-shape { display: inline-flex; margin: 0 0 16px; padding: 5px 8px; border-radius: 7px; background: color-mix(in srgb, var(--violet) 13%, var(--panel)); color: var(--copy-strong); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; }
.trace-values { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 7px; align-items: end; min-height: 110px; }
.trace-value { display: grid; gap: 6px; min-width: 0; text-align: center; }
.trace-value-bar-box { display: flex; align-items: end; justify-content: center; height: 57px; border-bottom: 1px solid var(--line); }
.trace-value-bar { display: block; width: min(100%, 35px); min-height: 4px; border-radius: 5px 5px 0 0; background: var(--blue); }
.trace-value-bar.negative { background: var(--accent-2); }
.trace-value b { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; font-variant-numeric: tabular-nums; }
.trace-value small { color: var(--muted); font-size: .67rem; }
.trace-no-values { align-self: center; grid-column: 1 / -1; padding: 10px; border: 1px dashed var(--line); border-radius: 8px; color: var(--muted); font-size: .84rem; text-align: center; }
.trace-card-note { min-height: 3em; margin: 14px 0 0; color: var(--muted); font-size: .75rem; line-height: 1.45; }
.trace-flow-arrow { align-self: center; color: var(--accent); font-size: 1.65rem; text-align: center; }
.trace-explanation { display: grid; grid-template-columns: minmax(0, 1.8fr) minmax(180px, 1fr); gap: 20px; margin: 24px 0 20px; }
.trace-explanation > div { padding-top: 17px; border-top: 1px solid var(--line); }
.trace-detail-label { color: var(--muted); font-size: .72rem; font-weight: 850; letter-spacing: .1em; text-transform: uppercase; }
.trace-explanation p { margin: 8px 0 0; color: var(--copy); line-height: 1.55; font-size: .89rem; }
.trace-stage-actions { display: flex; flex-wrap: wrap; gap: 8px; }
.trace-stage-actions button { padding: 9px 13px; border: 1px solid var(--line); border-radius: 9px; background: var(--panel-strong); color: var(--ink); cursor: pointer; font-size: .82rem; font-weight: 700; }
.trace-stage-actions button:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
.trace-stage-actions button:disabled { opacity: .45; cursor: not-allowed; }
.trace-stage-actions #nextStage, .trace-stage-actions #playStages { background: var(--accent); color: #fff; border-color: var(--accent); }
.trace-stage-actions #nextStage:hover:not(:disabled), .trace-stage-actions #playStages:hover { filter: brightness(1.08); color: #fff; }

.trace-controls { margin-top: 16px; padding: 22px; }
.trace-controls-header { display: flex; justify-content: space-between; align-items: baseline; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.trace-controls-header h2 { margin: 0; font-size: 1.15rem; }
.trace-controls-header p { margin: 0; color: var(--muted); font-size: .8rem; }
.trace-control-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 22px 28px; }
.trace-control-grid label { display: grid; gap: 9px; min-width: 0; }
.trace-control-grid label > span { font-size: .83rem; font-weight: 750; }
.trace-control-grid output { color: var(--accent); font-variant-numeric: tabular-nums; }
.trace-control-grid input { width: 100%; accent-color: var(--accent); cursor: pointer; }
.trace-control-grid small { color: var(--muted); font-size: .73rem; }

.trace-footer { display: flex; justify-content: space-between; gap: 22px; align-items: start; padding: 20px 0 0 272px; color: var(--muted); font-size: .78rem; line-height: 1.55; }
.trace-footer p { margin: 0; }
.trace-footer p:first-child { max-width: 65ch; }
.trace-footer p:last-child { flex: none; }

@media (max-width: 980px) {
  .trace-workspace { grid-template-columns: 1fr; }
  .trace-rail { position: static; max-height: none; }
  .trace-rail nav { display: flex; overflow-x: auto; gap: 4px; padding: 0 10px 11px; }
  .trace-phase-label { flex: none; align-self: center; margin: 0 5px; }
  .trace-stage-link { flex: none; width: 165px; }
  .trace-footer { padding-left: 0; }
}

@media (max-width: 700px) {
  .trace-shell { width: min(100% - 26px, 1480px); padding-top: 17px; }
  .trace-header { display: block; }
  .trace-top-links { margin-bottom: 20px; }
  .trace-theme { margin-top: 18px; }
  .trace-notice { display: block; }
  .trace-notice strong { display: block; margin-bottom: 3px; }
  .trace-example { grid-template-columns: repeat(2, 1fr); }
  .trace-example > div:first-child { grid-column: 1 / -1; }
  .trace-tensor-flow { grid-template-columns: 1fr; }
  .trace-flow-arrow { transform: rotate(90deg); line-height: 1; }
  .trace-card-header h3 { min-height: 0; }
  .trace-explanation { grid-template-columns: 1fr; gap: 10px; }
  .trace-control-grid { grid-template-columns: 1fr; }
  .trace-footer { display: block; }
  .trace-footer p + p { margin-top: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .trace-progress span { transition: none; }
}