/* ==========================================================================
   Interactive Laboratory
   Shared UI kit (assets/js/lab/_ui.js) and the visual language of each lab.
   Every colour comes from tokens.css (var(--c-…) / var(--dg-…)), so light and
   dark themes (data-theme and prefers-color-scheme) work without overrides.
   ========================================================================== */

/* ---------- Root ---------- */
.lab-root {
  --lab-gap: var(--sp-4);
  --lab-wood: color-mix(in srgb, var(--c-accent) 62%, var(--c-ink));
  --lab-rod: color-mix(in srgb, var(--c-ink) 45%, transparent);
  --lab-hl: color-mix(in srgb, var(--c-gold) 22%, var(--c-surface));
  container-type: inline-size;
  display: flex; flex-direction: column; gap: var(--lab-gap);
  min-width: 0;
  color: var(--c-ink); font-family: var(--font-sans); font-size: .95rem; line-height: 1.5;
}
.lab-root > * { margin: 0; min-width: 0; }
.lab-intro { font-family: var(--font-serif); font-size: 1.02rem; line-height: 1.65; color: var(--c-ink-soft); max-width: 78ch; }
.lab-h { font-family: var(--font-display); font-size: 1.28rem; font-weight: 600; line-height: 1.2; margin: 0; color: var(--c-ink); }
.lab-hint { font-size: .8rem; line-height: 1.45; color: var(--c-muted); }
.lab-mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.lab-strong { font-weight: 700; color: var(--c-ink); }
.lab-big { font-size: 1.18rem; font-weight: 600; line-height: 1.35; overflow-wrap: anywhere; }
.lab-note { font-family: var(--font-serif); font-size: .92rem; line-height: 1.62; color: var(--c-ink-soft); border-left: 3px solid var(--c-gold); padding: .2rem 0 .2rem 1rem; max-width: 82ch; }
.lab-note p { margin: 0 0 .6em; }
.lab-note p:last-child { margin-bottom: 0; }
.lab-note strong { color: var(--c-ink); }
.lab-warn {
  border: 1px solid color-mix(in srgb, var(--c-danger) 40%, var(--c-line)); border-left: 4px solid var(--c-danger);
  background: color-mix(in srgb, var(--c-danger) 8%, var(--c-surface)); border-radius: var(--radius-sm);
  padding: var(--sp-3) var(--sp-4); font-size: .9rem; line-height: 1.55;
}
.lab-warn strong { color: var(--c-danger); }

/* ---------- Layout helpers ---------- */
.lab-panel {
  background: var(--c-surface); border: 1px solid var(--c-line-soft); border-radius: var(--radius);
  padding: var(--sp-4) var(--sp-5); box-shadow: var(--shadow-1); min-width: 0;
}
.lab-panel > * { margin-block: 0; }
.lab-panel > * + * { margin-top: var(--sp-3); }
.lab-viz {
  background-color: var(--dg-bg);
  background-image:
    linear-gradient(color-mix(in srgb, var(--c-teal) 6%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--c-teal) 6%, transparent) 1px, transparent 1px);
  background-size: 20px 20px;
}
.lab-stack { display: flex; flex-direction: column; gap: var(--sp-3); min-width: 0; }
.lab-stack > *, .lab-stack > * + * { margin: 0; min-width: 0; }
.lab-root .lab-grid { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--lab-gap); align-items: start; }
.lab-scroll { overflow-x: auto; max-width: 100%; overscroll-behavior-x: contain; scrollbar-width: thin; }
.lab-svgwrap { overflow-x: auto; max-width: 100%; overscroll-behavior-x: contain; scrollbar-width: thin; }

/* ---------- Controls ---------- */
.lab-controls { display: flex; flex-wrap: wrap; align-items: flex-end; gap: var(--sp-3); }
.lab-controls > * { min-width: 0; max-width: 100%; }
.lab-field { display: flex; flex-direction: column; gap: .3rem; min-width: 0; max-width: 100%; }
.lab-field > label, .lab-field > .lab-hint:first-child { font-size: .78rem; font-weight: 650; letter-spacing: .01em; color: var(--c-ink-soft); line-height: 1.3; }
.lab-field > small.lab-hint { font-size: .76rem; }
.lab-field > textarea { width: 100%; }
/* A range with its live <output> on one row, label above. */
.lab-field:has(> .lab-range + output) { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; column-gap: .6rem; row-gap: .3rem; }
.lab-field:has(> .lab-range + output) > label { grid-column: 1 / -1; }
.lab-field > .lab-range + output { font-family: var(--font-mono); font-weight: 700; min-width: 2ch; text-align: right; color: var(--c-accent); }

.lab-input, .lab-select {
  min-height: 40px; max-width: 100%; padding: .45rem .7rem;
  border: 1px solid var(--c-line); border-radius: 8px; background: var(--c-bg); color: var(--c-ink);
  font: inherit; font-size: .92rem; line-height: 1.3;
  transition: border-color .15s, box-shadow .15s;
}
.lab-select { padding-right: 1.8rem; cursor: pointer; }
textarea.lab-input { display: block; width: 100%; min-height: 6.5rem; resize: vertical; line-height: 1.55; padding: .55rem .75rem; }
.lab-input:hover, .lab-select:hover { border-color: color-mix(in srgb, var(--c-teal) 45%, var(--c-line)); }
.lab-input:focus-visible, .lab-select:focus-visible { border-color: var(--c-teal); }
.lab-input[aria-invalid="true"] { border-color: var(--c-danger); box-shadow: inset 0 0 0 1px var(--c-danger); background: color-mix(in srgb, var(--c-danger) 6%, var(--c-bg)); }
.lab-input.lab-w-xs { width: 3.2rem; text-align: center; }
.lab-input.lab-w-sm { width: 6.75rem; }
.lab-input.lab-w-md { width: 12rem; }
.lab-range { width: 11rem; max-width: 100%; height: 40px; margin: 0; accent-color: var(--c-accent); cursor: pointer; background: transparent; }

.lab-btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .4rem;
  min-height: 40px; max-width: 100%; padding: .45rem 1rem;
  border: 1px solid var(--c-line); border-radius: 999px; background: var(--c-surface); color: var(--c-ink);
  font: inherit; font-size: .88rem; font-weight: 600; line-height: 1.2; text-align: center; cursor: pointer;
  transition: background-color .15s, border-color .15s, color .15s;
}
.lab-btn:hover { border-color: var(--c-accent); background: var(--c-surface-2); color: var(--c-ink); }
.lab-btn:active { transform: translateY(1px); }
.lab-btn:disabled { opacity: .5; cursor: not-allowed; }
.lab-btn--primary { background: var(--c-accent); border-color: var(--c-accent); color: var(--c-accent-ink); }
.lab-btn--primary:hover { background: var(--c-accent-strong); border-color: var(--c-accent-strong); color: var(--c-accent-ink); }
.lab-btn--ghost { background: transparent; }
.lab-btn[aria-pressed="true"] { background: var(--c-teal); border-color: var(--c-teal); color: var(--c-surface); }
.lab-btn[aria-pressed="true"]:hover { background: color-mix(in srgb, var(--c-teal) 85%, var(--c-ink)); color: var(--c-surface); }

.lab-check { display: inline-flex; align-items: center; gap: .45rem; min-height: 32px; font-size: .88rem; line-height: 1.35; cursor: pointer; }
.lab-check input { flex: none; width: 1.05rem; height: 1.05rem; margin: 0; accent-color: var(--c-accent); cursor: pointer; }
.lab-checks { display: flex; flex-wrap: wrap; gap: .15rem 1.1rem; }
.lab-fieldset { margin: 0; min-width: 0; padding: var(--sp-2) var(--sp-4) var(--sp-3); border: 1px solid var(--c-line-soft); border-radius: var(--radius); background: var(--c-surface); }
.lab-fieldset > legend { padding: 0 .4rem; font-size: .8rem; font-weight: 650; color: var(--c-ink-soft); }

/* Visible focus for every control, also on the dark presenter stage. */
.lab-root :focus-visible { outline: 2px solid var(--c-teal); outline-offset: 2px; box-shadow: var(--focus-ring); }
.lab-root summary:focus-visible { border-radius: 4px; }

/* ---------- Status line ---------- */
.lab-status {
  min-height: 2.6rem; padding: .55rem .9rem;
  border: 1px solid var(--c-line-soft); border-left: 4px solid var(--c-teal); border-radius: var(--radius-sm);
  background: var(--c-surface); color: var(--c-ink); font-size: .9rem; line-height: 1.5; overflow-wrap: anywhere;
}
.lab-status:empty { min-height: 0; padding: 0; border: 0; background: none; }
.lab-status.is-ok { border-left-color: var(--c-success); background: color-mix(in srgb, var(--c-success) 9%, var(--c-surface)); }
.lab-status.is-err { border-left-color: var(--c-danger); background: color-mix(in srgb, var(--c-danger) 9%, var(--c-surface)); }
.lab-status.is-warn { border-left-color: var(--c-warn); background: color-mix(in srgb, var(--c-warn) 11%, var(--c-surface)); }

/* ---------- Registers / key–value tiles ---------- */
.lab-kv { display: flex; flex-wrap: wrap; gap: .5rem; }
.lab-reg {
  display: inline-flex; flex-direction: column; gap: .1rem; min-width: 4.5rem; max-width: 100%;
  padding: .35rem .7rem; border: 1px solid var(--c-line-soft); border-radius: var(--radius-sm); background: var(--c-surface);
}
.lab-reg > span { font-size: .7rem; font-weight: 650; letter-spacing: .04em; color: var(--c-muted); }
.lab-reg > b { font-size: 1rem; color: var(--c-ink); overflow-wrap: anywhere; }
.lab-reg.is-secret { border-color: color-mix(in srgb, var(--c-danger) 45%, var(--c-line)); background: color-mix(in srgb, var(--c-danger) 7%, var(--c-surface)); }
.lab-reg.is-secret > span { color: var(--c-danger); }

/* ---------- Tables ---------- */
.lab-table { border-collapse: collapse; background: var(--c-surface); font-size: .86rem; line-height: 1.35; }
.lab-table caption { caption-side: top; min-width: 15rem; text-align: left; padding: 0 0 .4rem; font-family: var(--font-sans); font-size: .78rem; line-height: 1.4; color: var(--c-muted); }
.lab-table th, .lab-table td { padding: .32rem .6rem; border: 1px solid var(--c-line-soft); vertical-align: middle; }
.lab-table thead th { position: sticky; top: 0; z-index: 1; background: var(--c-surface-2); color: var(--c-ink-soft); font-size: .78rem; font-weight: 650; white-space: nowrap; }
.lab-table tbody th { text-align: left; font-weight: 600; color: var(--c-ink-soft); background: color-mix(in srgb, var(--c-surface-2) 55%, var(--c-surface)); white-space: nowrap; }
.lab-table.lab-center td, .lab-table.lab-center thead th { text-align: center; }
.lab-table tr.is-current > td, .lab-table tr.is-current > th { background: var(--lab-hl); }
.lab-table tr.is-current > :first-child { box-shadow: inset 3px 0 0 var(--c-accent); }
.lab-table tr.is-removed > td { color: var(--c-muted); text-decoration: line-through; text-decoration-color: color-mix(in srgb, var(--c-danger) 60%, transparent); }
.lab-table .lab-input, .lab-table .lab-select { min-height: 34px; padding: .2rem .45rem; font-size: .86rem; }
.lab-table .lab-btn { min-height: 32px; padding: .15rem .65rem; }

/* ---------- Lists, details, code, legends ---------- */
.lab-steps { margin: 0; padding-left: 1.5rem; display: grid; gap: .3rem; }
.lab-steps > li { padding: .25rem .5rem; border-radius: var(--radius-sm); overflow-wrap: anywhere; }
.lab-steps > li.is-done { color: var(--c-muted); }
.lab-steps > li.is-done::marker { content: '✓  '; color: var(--c-success); }
.lab-steps > li.is-current { background: var(--lab-hl); box-shadow: inset 3px 0 0 var(--c-accent); }
.lab-steps strong { color: var(--c-accent); }
.lab-details { padding: 0 var(--sp-4); border: 1px solid var(--c-line-soft); border-radius: var(--radius); background: var(--c-surface); }
.lab-details.lab-panel { padding-block: 0; }
.lab-details > summary { padding: .65rem 0; font-weight: 650; cursor: pointer; overflow-wrap: anywhere; }
.lab-details > summary:hover { color: var(--c-accent); }
.lab-details[open] { padding-bottom: var(--sp-3); }
.lab-details > :not(summary) { margin: 0; }
.lab-details > :not(summary) + * { margin-top: var(--sp-2); }
.lab-details.is-final { border-color: color-mix(in srgb, var(--c-teal) 60%, var(--c-line)); box-shadow: inset 4px 0 0 var(--c-teal), var(--shadow-1); }
.lab-code { margin: 0; white-space: pre-wrap; overflow-wrap: anywhere; font-size: .86rem; }
.lab-legend { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: .35rem 1.1rem; font-size: .8rem; color: var(--c-ink-soft); }
.lab-legend > * { display: inline-flex; align-items: center; gap: .4rem; }
.lab-swatch { display: inline-block; flex: none; width: .9rem; height: .9rem; border-radius: 3px; border: 1px solid color-mix(in srgb, var(--c-ink) 22%, transparent); }

/* ---------- SVG basics ---------- */
.lab-svg { display: block; width: 100%; height: auto; max-width: 100%; margin-inline: auto; overflow: visible; font-family: var(--font-sans); user-select: none; }
.lab-svg text { fill: var(--dg-ink); font-size: 13px; }
.lab-svg .lab-svg-label { fill: var(--dg-muted); font-size: 11px; }

/* ==========================================================================
   Individual labs
   ========================================================================== */

/* ---------- Abacus ---------- */
.lab-abacus-frame {
  --bead-h: 24px;
  display: flex; justify-content: center; max-width: 34rem; margin-inline: auto; padding: .5rem 0 .35rem;
  border: 10px solid var(--lab-wood); border-radius: 12px; background: var(--dg-panel);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--c-ink) 22%, transparent), var(--shadow-1);
}
.lab-abacus-rod { flex: 1 1 0; min-width: 0; max-width: 4.2rem; display: flex; flex-direction: column; border-radius: 4px; }
.lab-abacus-rod.is-focus { background: color-mix(in srgb, var(--c-gold) 24%, transparent); }
.lab-abacus-deck {
  display: flex; flex-direction: column; align-items: center;
  height: calc((var(--beads) + 1) * (var(--bead-h) + 2px));
  background: linear-gradient(90deg, transparent calc(50% - 1.5px), var(--lab-rod) calc(50% - 1.5px), var(--lab-rod) calc(50% + 1.5px), transparent calc(50% + 1.5px));
}
.lab-abacus-gap { flex: 1 1 auto; min-height: 0; }
.lab-abacus-bead {
  flex: none; width: min(88%, 3.1rem); height: var(--bead-h); margin: 1px 0; padding: 0;
  border: 1px solid color-mix(in srgb, var(--lab-wood) 75%, var(--c-ink)); border-radius: 50%;
  background: radial-gradient(ellipse at 50% 30%, color-mix(in srgb, var(--c-accent) 22%, var(--c-surface)), color-mix(in srgb, var(--c-accent) 45%, var(--c-surface-2)));
  cursor: pointer; transition: background-color .15s, filter .15s;
}
.lab-abacus-bead:hover { filter: brightness(1.08) saturate(1.1); }
.lab-abacus-bead.is-active {
  border-color: var(--c-accent-strong);
  background: radial-gradient(ellipse at 50% 30%, color-mix(in srgb, var(--c-gold) 65%, var(--c-surface)), var(--c-accent) 75%);
}
.lab-abacus-beam { height: 8px; margin: 2px 0; background: var(--lab-wood); }
.lab-abacus-digit { padding-top: .35rem; text-align: center; font-family: var(--font-mono); font-weight: 700; font-size: 1rem; color: var(--c-ink); }
.lab-abacus-readout { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: .3rem 1rem; }
.lab-abacus-value { font-size: .95rem; }
.lab-abacus-value strong { font-size: 1.5rem; color: var(--c-accent); }
.lab-abacus-readout .lab-hint { overflow-wrap: anywhere; }

/* ---------- Binary ---------- */
.lab-binary-fields > .lab-field { flex: 1 1 10rem; }
.lab-binary-fields > .lab-field:nth-child(2) { flex: 2 1 18rem; }
.lab-binary-fields .lab-input { width: 100%; }
.lab-binary-bits { display: flex; flex-wrap: wrap; justify-content: center; gap: .55rem .8rem; }
.lab-binary-nibble { display: inline-flex; gap: 3px; }
.lab-binary-bit {
  display: inline-flex; flex-direction: column; align-items: center; justify-content: center; gap: 1px;
  width: 2.6rem; min-height: 3.3rem; padding: .25rem .1rem; overflow: hidden;
  border: 1px solid var(--c-line); border-radius: 6px; background: var(--c-surface); color: var(--c-ink); cursor: pointer;
  transition: background-color .15s, border-color .15s, color .15s;
}
.lab-binary-bit:hover { border-color: var(--c-accent); }
.lab-binary-bit.is-on { background: var(--c-accent); border-color: var(--c-accent-strong); color: var(--c-accent-ink); }
.lab-binary-digit { font-family: var(--font-mono); font-size: 1.25rem; font-weight: 700; line-height: 1.1; }
.lab-binary-place { max-width: 100%; font-family: var(--font-mono); font-size: .6rem; line-height: 1.2; opacity: .85; white-space: nowrap; }
.lab-binary-sum { text-align: center; color: var(--c-ink-soft); overflow-wrap: anywhere; }

/* ---------- Logic gates ---------- */
.lab-logic .lab-viz { overflow-x: auto; }
.lab-logic-gate { max-width: 440px; }
.lab-logic-half { max-width: 560px; }
.lab-logic-full { max-width: 780px; }
.lab-logic-toggle { min-width: 5.5rem; font-family: var(--font-mono); }
.lab-logic-toggle[aria-pressed="true"], .lab-logic-toggle[aria-pressed="true"]:hover { background: var(--c-accent); border-color: var(--c-accent-strong); color: var(--c-accent-ink); }
.lab-wire { fill: none; stroke: var(--dg-muted); stroke-width: 2.5; stroke-linecap: round; stroke-linejoin: round; }
.lab-wire.is-on { stroke: var(--dg-accent); stroke-width: 3.2; }
.lab-gate-body { fill: var(--dg-panel); stroke: var(--dg-ink); stroke-width: 2; stroke-linejoin: round; }
.lab-gate-line { fill: none; stroke: var(--dg-ink); stroke-width: 2; }
.lab-dot { fill: var(--dg-muted); }
.lab-dot.is-on { fill: var(--dg-accent); }
.lab-lamp circle { fill: var(--dg-soft); stroke: var(--dg-ink); stroke-width: 1.5; }
.lab-lamp.is-on circle { fill: var(--dg-gold); stroke: var(--dg-accent); stroke-width: 2; filter: drop-shadow(0 0 5px color-mix(in srgb, var(--dg-gold) 75%, transparent)); }
.lab-svg .lab-lamp-val { font-family: var(--font-mono); font-size: 11px; font-weight: 700; fill: var(--dg-ink); }
.lab-svg .lab-lamp.is-on .lab-lamp-val { fill: var(--c-midnight); }

/* ---------- Turing machine ---------- */
.lab-turing-tape { display: flex; justify-content: center; gap: 3px; padding: 1.5rem 0 .3rem; overflow: hidden; }
.lab-turing-cell {
  position: relative; flex: 0 1 2.6rem; min-width: 0; height: 3.2rem; padding-bottom: .55rem;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  border: 1px solid var(--dg-line); border-radius: 5px; background: var(--dg-panel); font-size: 1.15rem; font-weight: 700;
}
.lab-turing-cell.is-blank { color: var(--c-muted); font-weight: 400; }
.lab-turing-cell.is-head { border: 2px solid var(--c-accent); background: color-mix(in srgb, var(--c-gold) 24%, var(--dg-panel)); }
.lab-turing-headmark { position: absolute; top: -1.4rem; left: 50%; transform: translateX(-50%); color: var(--c-accent); font-size: .95rem; line-height: 1; }
.lab-turing-idx { position: absolute; bottom: 2px; left: 0; right: 0; text-align: center; font-family: var(--font-mono); font-size: .58rem; font-weight: 400; color: var(--c-muted); }
.lab-turing-rules td { padding: .2rem .3rem; }
.lab-turing .lab-viz > .lab-kv { margin-top: var(--sp-3); justify-content: center; }

/* ---------- Finite-state machine ---------- */
.lab-fsm-input { display: flex; flex-wrap: wrap; justify-content: center; gap: .3rem; min-height: 2.3rem; }
.lab-fsm-sym {
  display: inline-grid; place-items: center; min-width: 2rem; height: 2.2rem; padding: 0 .45rem;
  border: 1px solid var(--c-line); border-radius: var(--radius-sm); background: var(--c-surface);
  font-family: var(--font-mono); font-weight: 700;
}
.lab-fsm-sym.is-read { opacity: .45; background: var(--c-surface-2); }
.lab-fsm-sym.is-next { border-color: var(--c-accent); box-shadow: 0 0 0 2px color-mix(in srgb, var(--c-accent) 35%, transparent); }
.lab-fsm .lab-svg { max-width: 640px; }
.lab-edge { fill: none; stroke: var(--dg-muted); stroke-width: 1.8; }
.lab-edge.is-on { stroke: var(--dg-accent); stroke-width: 3; }
.lab-arrowhead { fill: var(--dg-muted); }
.lab-arrowhead.is-on { fill: var(--dg-accent); }
.lab-svg .lab-edge-label { font-family: var(--font-mono); font-size: 13px; font-weight: 600; fill: var(--dg-ink); paint-order: stroke; stroke: var(--dg-bg); stroke-width: 4px; stroke-linejoin: round; }
.lab-svg .lab-edge-label.is-on { fill: var(--dg-accent); }
.lab-node circle { fill: var(--dg-panel); stroke: var(--dg-ink); stroke-width: 2; }
.lab-node .lab-node-inner { fill: none; stroke-width: 1.5; }
.lab-svg .lab-node text { font-family: var(--font-mono); font-size: 15px; font-weight: 700; }
.lab-node.is-current circle { fill: color-mix(in srgb, var(--dg-gold) 32%, var(--dg-panel)); stroke: var(--dg-accent); stroke-width: 3; }
.lab-node.is-accept circle { fill: color-mix(in srgb, var(--c-success) 28%, var(--dg-panel)); stroke: var(--c-success); }
.lab-node.is-reject circle { fill: color-mix(in srgb, var(--c-danger) 22%, var(--dg-panel)); stroke: var(--c-danger); }

/* ---------- Stored-program CPU ---------- */
.lab-cpu-src { min-height: 14rem; font-size: .85rem; }
.lab-cpu-phases { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: .4rem; counter-reset: lab-phase; }
.lab-cpu-phases > li {
  counter-increment: lab-phase; padding: .3rem .85rem; border: 1px solid var(--c-line); border-radius: 999px;
  background: var(--c-surface); color: var(--c-muted); font-size: .82rem; font-weight: 650;
}
.lab-cpu-phases > li::before { content: counter(lab-phase) '. '; }
.lab-cpu-phases > li.is-done { color: var(--c-ink-soft); background: var(--c-teal-soft); border-color: color-mix(in srgb, var(--c-teal) 45%, var(--c-line)); }
.lab-cpu-phases > li.is-next { color: var(--c-accent-ink); background: var(--c-accent); border-color: var(--c-accent); }
.lab-cpu-mem { display: grid; grid-template-columns: repeat(auto-fill, minmax(4.3rem, 1fr)); gap: 4px; }
.lab-cpu-cell {
  display: grid; min-width: 0; padding: .22rem .35rem; line-height: 1.2;
  border: 1px solid var(--c-line-soft); border-radius: 5px; background: var(--c-surface);
}
.lab-cpu-addr { font-family: var(--font-mono); font-size: .62rem; color: var(--c-muted); }
.lab-cpu-word { font-size: .95rem; font-weight: 700; }
.lab-cpu-dis { font-size: .64rem; color: var(--c-ink-soft); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.lab-cpu-cell.is-pc { border-color: var(--c-accent); box-shadow: inset 0 0 0 1px var(--c-accent); }
.lab-cpu-cell.is-read { background: var(--c-teal-soft); }
.lab-cpu-cell.is-write { background: var(--c-gold-soft); border-color: var(--c-gold); box-shadow: inset 0 0 0 1px var(--c-gold); }
.lab-cpu-out { display: inline; font-weight: 700; color: var(--c-accent); overflow-wrap: anywhere; }

/* ---------- Sorting ---------- */
.lab-sort-bars {
  display: flex; align-items: flex-end; gap: 2px; height: 220px; height: clamp(170px, 32cqi, 260px);
  padding-top: 1.3rem; border-bottom: 2px solid var(--dg-line);
}
.lab-sort-bar { position: relative; flex: 1 1 0; min-width: 2px; border-radius: 3px 3px 0 0; background: color-mix(in srgb, var(--dg-blue) 55%, var(--dg-panel)); }
.lab-sort-bar > span { position: absolute; bottom: 100%; left: 50%; transform: translateX(-50%); padding-bottom: 2px; font-family: var(--font-mono); font-size: .66rem; line-height: 1; color: var(--c-ink-soft); }
.lab-sort-bar.is-dim { opacity: .35; }
/* Order matters: a bar can carry several of these; the later one wins. */
.lab-sort-sorted { background: var(--c-success); }
.lab-sort-compare { background: var(--dg-gold); }
.lab-sort-pivot { background: var(--dg-ink); }
.lab-sort-swap { background: var(--dg-red); }
.lab-sorting .lab-viz > .lab-kv + * { margin-top: var(--sp-2); }

/* ---------- Graph search ---------- */
.lab-graph .lab-svg, .lab-packets .lab-svg { max-width: 700px; }
.lab-gedge { stroke: var(--dg-line); stroke-width: 3; stroke-linecap: round; }
.lab-gedge.is-tree { stroke: var(--dg-teal); }
.lab-gedge.is-relaxed { stroke: var(--dg-gold); stroke-width: 4; stroke-dasharray: 7 5; }
.lab-gedge.is-path { stroke: var(--dg-accent); stroke-width: 6; }
.lab-gw-bg { fill: var(--dg-bg); stroke: var(--dg-line); stroke-width: 1; }
.lab-svg .lab-gw { font-family: var(--font-mono); font-size: 12px; font-weight: 700; fill: var(--dg-ink); }
.lab-gnode circle { fill: var(--dg-panel); stroke: var(--dg-ink); stroke-width: 2; }
.lab-svg .lab-gnode > text:not(.lab-svg-label) { font-size: 15px; font-weight: 700; }
.lab-svg .lab-gnode > .lab-svg-label { paint-order: stroke; stroke: var(--dg-bg); stroke-width: 4px; stroke-linejoin: round; }
.lab-gnode.is-front circle { fill: color-mix(in srgb, var(--dg-teal) 24%, var(--dg-panel)); stroke: var(--dg-teal); stroke-width: 3; }
.lab-gnode.is-cur circle { fill: var(--dg-gold); stroke: var(--dg-accent); stroke-width: 3.5; }
.lab-svg .lab-gnode.is-cur > text:not(.lab-svg-label) { fill: var(--c-midnight); }
.lab-gnode.is-done circle { fill: var(--dg-soft); stroke: var(--dg-muted); }
.lab-gnode.is-path circle { fill: var(--dg-accent); stroke: var(--dg-ink); stroke-width: 2.5; }
.lab-svg .lab-gnode.is-path > text:not(.lab-svg-label) { fill: var(--c-accent-ink); }
.lab-graph-cur { background: var(--dg-gold); }
.lab-graph-front { background: color-mix(in srgb, var(--dg-teal) 24%, var(--dg-panel)); border-color: var(--dg-teal); }
.lab-graph-done { background: var(--dg-soft); }
.lab-graph-path { background: var(--dg-accent); }

/* ---------- Packet switching ---------- */
.lab-plink { stroke: var(--dg-line); stroke-width: 5; stroke-linecap: round; cursor: pointer; transition: stroke .15s; }
.lab-plink:hover { stroke: var(--dg-teal); }
.lab-plink.is-circuit { stroke: var(--dg-teal); stroke-width: 7; }
.lab-plink.is-down { stroke: var(--dg-red); stroke-width: 4; stroke-dasharray: 2 9; opacity: .85; }
.lab-packets .lab-svg text, .lab-packet { pointer-events: none; }
.lab-packets .lab-svg .lab-svg-label { paint-order: stroke; stroke: var(--dg-bg); stroke-width: 3px; stroke-linejoin: round; }
.lab-router rect { fill: var(--dg-panel); stroke: var(--dg-ink); stroke-width: 2; }
.lab-svg .lab-router text { font-size: 14px; font-weight: 700; }
.lab-router.is-end rect { fill: var(--dg-ink); }
.lab-svg .lab-router.is-end text { fill: var(--dg-panel); }
.lab-packet circle { fill: var(--dg-accent); stroke: var(--dg-panel); stroke-width: 2; }
.lab-svg .lab-packet text { font-family: var(--font-mono); font-size: 10px; font-weight: 700; fill: var(--c-accent-ink); }
.lab-packet.is-lost circle { fill: var(--dg-red); opacity: .55; }
.lab-pkt-slots { display: flex; flex-wrap: wrap; gap: .35rem; }
.lab-pkt-slot {
  display: inline-flex; flex-direction: column; align-items: center; min-width: 3.4rem; padding: .3rem .45rem;
  border: 1px dashed var(--c-line); border-radius: var(--radius-sm); background: var(--c-surface-2);
}
.lab-pkt-slot.is-in { border-style: solid; border-color: var(--c-teal); background: var(--c-teal-soft); }
.lab-pkt-seq { font-size: .68rem; font-weight: 700; color: var(--c-muted); }
.lab-pkt-slot > .lab-mono { font-weight: 700; white-space: pre; }

/* ---------- Caesar cipher ---------- */
.lab-caesar-wheel .lab-table th, .lab-caesar-wheel .lab-table td { padding: .25rem .4rem; min-width: 1.7rem; }
.lab-caesar-wheel td.lab-strong { color: var(--c-accent); }
.lab-caesar-out {
  display: block; min-height: 3rem; padding: .6rem .8rem; border: 1px solid var(--c-line); border-radius: 8px;
  background: var(--c-surface-2); white-space: pre-wrap; overflow-wrap: anywhere; line-height: 1.55;
}
.lab-caesar-bar-ref { fill: color-mix(in srgb, var(--dg-muted) 45%, transparent); }
.lab-caesar-bar-cipher { fill: var(--dg-accent); }
.lab-caesar-grid { stroke: var(--dg-line); stroke-width: 1; stroke-dasharray: 3 4; }
.lab-caesar-sw-ref { background: color-mix(in srgb, var(--dg-muted) 45%, transparent); }
.lab-caesar-sw-cipher { background: var(--dg-accent); }

/* ---------- Difference Engine ---------- */
.lab-de-engine { display: flex; justify-content: center; gap: var(--sp-3); }
.lab-de-col {
  flex: 0 1 8rem; min-width: 0; display: flex; flex-direction: column; align-items: center; gap: .45rem;
  padding: .6rem .5rem; border: 1px solid var(--c-line); border-radius: var(--radius-sm); background: var(--c-surface); text-align: center;
}
.lab-de-col.is-const { border-color: var(--c-teal); box-shadow: inset 0 3px 0 var(--c-teal); }
.lab-de-name { font-family: var(--font-mono); font-weight: 700; color: var(--c-accent); }
/* Each column is a vertical stack of figure wheels, most significant digit on top, as on Babbage’s engine. */
.lab-de-wheels { display: flex; flex-direction: column; align-items: center; gap: 3px; }
.lab-de-wheel {
  display: grid; place-items: center; width: 2.1rem; height: 1.75rem; border-radius: 5px;
  border: 1px solid color-mix(in srgb, var(--c-gold) 65%, var(--c-ink));
  background: linear-gradient(180deg, color-mix(in srgb, var(--c-gold) 32%, var(--c-surface)), var(--c-gold-soft) 45%, color-mix(in srgb, var(--c-gold) 32%, var(--c-surface)));
  color: var(--c-ink); font-size: 1.05rem; font-weight: 700;
}
.lab-de-sign { font-weight: 700; font-size: 1.1rem; color: var(--c-danger); }
.lab-de-col > .lab-hint { font-size: .72rem; }
.lab-de-history { max-height: 22rem; overflow: auto; border: 1px solid var(--c-line-soft); border-radius: var(--radius-sm); }
.lab-de-history > .lab-table { width: 100%; }
.lab-de-history > .lab-hint { margin: .5rem .6rem; }
.lab-de-carry td.is-on { color: var(--c-accent); font-weight: 700; font-size: .78rem; }

/* ---------- SQL ---------- */
.lab-sql-table { font-size: .8rem; }
.lab-sql-table thead th { font-family: var(--font-mono); font-size: .72rem; font-weight: 600; }
.lab-sql-table td { white-space: nowrap; }

/* ---------- Perceptron ---------- */
.lab-perc-plot .lab-svg { max-width: 420px; cursor: crosshair; border-radius: var(--radius-sm); }
.lab-perc-bg { fill: var(--dg-panel); }
.lab-perc-pos { fill: color-mix(in srgb, var(--dg-teal) 18%, transparent); }
.lab-perc-axis { stroke: var(--dg-line); stroke-width: 1; stroke-dasharray: 4 4; }
.lab-perc-line { stroke: var(--dg-accent); stroke-width: 3; stroke-linecap: round; }
.lab-perc-pt > * { stroke: var(--dg-panel); stroke-width: 2; }
.lab-perc-pt.is-pos > circle { fill: var(--dg-teal); }
.lab-perc-pt.is-neg > rect { fill: var(--dg-gold); }
.lab-perc-pt.is-wrong > * { stroke: var(--dg-red); stroke-width: 3.5; }
.lab-perc-pt.is-cur > * { stroke-width: 3.5; }
.lab-perc-pt.is-cur:not(.is-wrong) > * { stroke: var(--dg-ink); }

/* ==========================================================================
   Container-responsive layout (the lab may sit in the page column or a slide)
   ========================================================================== */
@container (min-width: 760px) {
  .lab-root .lab-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); }
  .lab-root .lab-cpu-grid { grid-template-columns: minmax(0, .9fr) minmax(0, 1.1fr); }
}
@container (max-width: 560px) {
  .lab-root { --lab-gap: var(--sp-3); }
  .lab-panel { padding: var(--sp-3); }
  .lab-details { padding-inline: var(--sp-3); }
  .lab-fieldset { padding-inline: var(--sp-3); }
  .lab-intro { font-size: .98rem; }
  /* Keep diagram labels legible: scroll sideways instead of shrinking below ~0.8×. */
  .lab-graph .lab-svgwrap > .lab-svg, .lab-packets .lab-svgwrap > .lab-svg, .lab-fsm .lab-svgwrap > .lab-svg { min-width: 440px; }
  .lab-caesar-hist { min-width: 520px; }
  .lab-logic-full { min-width: 460px; }
  .lab-logic-half { min-width: 330px; }
  /* Show 9 tape cells around the head instead of 15. */
  .lab-turing-cell:nth-child(-n+3), .lab-turing-cell:nth-last-child(-n+3) { display: none; }
  .lab-binary-bits { gap: .45rem .6rem; }
  .lab-binary-bit { width: 2.05rem; min-height: 3rem; }
  .lab-binary-digit { font-size: 1.1rem; }
  .lab-binary-place { font-size: .5rem; }
  .lab-de-engine { gap: var(--sp-2); }
  .lab-de-col { padding: .5rem .25rem; }
  .lab-de-col > .lab-hint { font-size: .64rem; }
  .lab-de-wheel { width: 1.8rem; height: 1.6rem; font-size: .95rem; }
  .lab-abacus-frame { --bead-h: 22px; border-width: 8px; }
  .lab-range { width: 9rem; }
}

/* ==========================================================================
   Presenter: a live lab on a slide (.slide-lab) — self-contained card so it
   reads the same on the dark or light stage and in either site theme.
   ========================================================================== */
.slide-lab {
  padding: var(--sp-4); border: 1px solid var(--c-line); border-radius: var(--radius);
  background: var(--c-bg); color: var(--c-ink); box-shadow: var(--shadow-2); text-align: left; font-size: 1rem;
}
.slide-lab .lab-root { padding-right: .25rem; overscroll-behavior: contain; scrollbar-width: thin; }
.slide-lab .lab-note { font-size: .88rem; }

/* ---------- Reduced motion ---------- */
.lab-root[data-reduced-motion="true"] *, .lab-root[data-reduced-motion="true"] *::before, .lab-root[data-reduced-motion="true"] *::after { transition: none !important; animation: none !important; }
@media (prefers-reduced-motion: reduce) {
  .lab-root *, .lab-root *::before, .lab-root *::after { transition: none !important; animation: none !important; }
  .lab-btn:active { transform: none; }
}

/* ---------- Forced colours (Windows high contrast) ---------- */
@media (forced-colors: active) {
  .lab-binary-bit.is-on, .lab-abacus-bead.is-active, .lab-btn[aria-pressed="true"], .lab-fsm-sym.is-next, .lab-cpu-cell.is-pc, .lab-turing-cell.is-head { outline: 3px solid Highlight; outline-offset: -3px; }
  .lab-table tr.is-current > * { outline: 1px solid Highlight; }
}

/* ---------- Print ---------- */
@media print {
  .lab-controls, .lab-btn { display: none !important; }
  .lab-panel, .lab-viz { box-shadow: none; background: none; }
}