/* Figure 4. One cube, two blocks: the cube's own acts as strings of flips and signs; one switch for the first block's sign.
   Every class is prefixed bi4-. Magenta = flips (acts that write); green = commute (accepted), red = does not commute and the
   carried sign (rejected); ink = structure. */
.bi4 {
  --k-paper: var(--bi-paper, #faf8f3); --k-ink: var(--bi-ink, #1d1d1b); --k-body: var(--bi-body, #2a2926); --k-soft: var(--bi-soft, #3c3a36);
  --k-hair: var(--bi-hair, #8a8a8a); --k-rule: var(--bi-rule, color-mix(in srgb, var(--k-ink) 16%, var(--k-paper)));
  --k-c: var(--bi-cyan, #009fe3); --k-m: var(--bi-magenta, #e6007e); --k-c-text: var(--bi-cyan-text, #0072b5); --k-m-text: var(--bi-magenta-text, #c4006b);
  --k-m-tint: color-mix(in srgb, var(--k-m) 8%, var(--k-paper)); --k-ok: #0b7a3e; --k-no: #c8401f;
  --k-text: var(--bi-text, "InterVariable", "Inter", -apple-system, "Helvetica Neue", Arial, sans-serif);
  --k-display: var(--bi-display, "Inter Display", "InterVariable", "Inter", -apple-system, "Helvetica Neue", Arial, sans-serif);
  --k-mono: var(--bi-mono, "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace);
  container-type: inline-size;
  margin: 0; padding: clamp(.9rem, 1.8vw, 1.25rem); background: var(--k-paper); color: var(--k-body);
  border: 1px solid var(--k-ink); font-family: var(--k-text); font-weight: 420; line-height: 1.42;
  font-optical-sizing: auto; box-sizing: border-box; position: relative;
}
@media screen and (prefers-color-scheme: dark) {
  .bi4 { --k-paper: var(--bi-paper, #141413); --k-ink: var(--bi-ink, #faf8f3); --k-body: var(--bi-body, #e9e6df); --k-soft: var(--bi-soft, #c9c5bc);
    --k-c: var(--bi-cyan, #2bb3f0); --k-m: var(--bi-magenta, #ff3d9e); --k-c-text: var(--bi-cyan-text, #2bb3f0); --k-m-text: var(--bi-magenta-text, #ff6fb6);
    --k-m-tint: color-mix(in srgb, var(--k-m) 13%, var(--k-paper)); --k-ok: #3fcf7f; --k-no: #ff6a3d; }
}
.bi4 *, .bi4 *::before, .bi4 *::after { box-sizing: border-box; }
.bi4-label { margin: 0; font: 700 .7rem/1.3 var(--k-mono); letter-spacing: .14em; text-transform: uppercase; color: var(--k-soft); }
.bi4-ink { color: var(--k-ink); }
.bi4-head { display: flex; flex-wrap: wrap; justify-content: space-between; gap: .5rem 1rem; align-items: baseline;
  padding-bottom: .7rem; margin-bottom: .9rem; border-bottom: 1px solid var(--k-rule); }
.bi4-head .bi4-live { color: var(--k-ink); }
.bi4-live::before { content: ""; display: inline-block; width: .5rem; height: .5rem; margin-right: .45rem; background: var(--k-m); vertical-align: .05rem; }
.bi4-lede { margin: 0 0 .9rem; max-width: 52rem; font-size: 1.05rem; font-weight: 450; line-height: 1.32; color: var(--k-ink); }
.bi4-ctl { display: flex; flex-wrap: wrap; gap: .8rem 2rem; align-items: flex-end; margin-bottom: .9rem; }
.bi4-ctl .bi4-label { margin-bottom: .35rem; }
.bi4-seg { display: inline-flex; flex-wrap: wrap; border: 1px solid var(--k-ink); }
.bi4-seg button { appearance: none; border: 0; border-radius: 0; background: transparent; color: var(--k-ink); cursor: pointer;
  font: 700 .66rem/1 var(--k-mono); letter-spacing: .1em; text-transform: uppercase; padding: .6rem .85rem; min-height: 36px; }
.bi4-seg button + button { border-left: 1px solid var(--k-ink); }
.bi4-seg button[aria-pressed="true"] { background: var(--k-ink); color: var(--k-paper); }
.bi4-seg button:hover:not([aria-pressed="true"]) { background: color-mix(in srgb, var(--k-ink) 8%, transparent); }
.bi4-seg button:focus-visible { outline: 2px solid var(--k-ink); outline-offset: 2px; }
.bi4-seg-s button { font-size: .6rem; padding: .5rem .65rem; min-height: 32px; }
.bi4-cubenote { margin: .3rem 0 0; font-size: .74rem; color: var(--k-soft); max-width: 16rem; }
.bi4-grid { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr); gap: 1rem clamp(1rem, 2.5vw, 2rem); align-items: start; }
.bi4-box { min-width: 0; }
.bi4-box .bi4-label { margin-bottom: .45rem; }
.bi4-tw { overflow-x: auto; max-width: 100%; position: relative; }
.bi4-str { border-collapse: collapse; font: 400 .76rem/1.2 var(--k-mono); color: var(--k-ink); }
.bi4-str th, .bi4-str td { padding: 0; }
.bi4-str thead th { font-size: .58rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--k-soft); padding: .15rem .1rem; text-align: center; white-space: nowrap; }
.bi4-str thead th.blk { border-bottom: 2px solid var(--k-ink); }
.bi4-str thead th.axl { text-align: right; padding-right: .7rem; }
.bi4-str tbody th { text-align: left; font-size: .7rem; font-weight: 700; padding: .2rem .7rem .2rem 0; white-space: nowrap; }
.bi4-str td { width: 2.3rem; height: 2.1rem; text-align: center; vertical-align: middle; border: 1px solid var(--k-rule); font-size: 1.05rem; font-weight: 700; }
.bi4-str td.gap, .bi4-str th.gap { width: .7rem; border: 0; }
.bi4-str td.flip { color: var(--k-m-text); background: var(--k-m-tint); border-color: var(--k-m); }
.bi4-str td.sign { color: var(--k-ink); }
.bi4-str td.car { color: var(--k-no); outline: 2px solid var(--k-no); outline-offset: -3px; }
.bi4-str td.none, .bi4-str td.off { color: var(--k-soft); font-weight: 400; }
.bi4-str td.off { border-style: dashed; }
.bi4-str tr.sec th { color: var(--k-ink); }
.bi4-str tr.ref th, .bi4-str tr.ref td { opacity: .75; }
.bi4-str tr.ref th { font-weight: 400; color: var(--k-soft); padding-top: .55rem; }
.bi4-str tr.ref td { border-top: 0; }
.bi4-key { display: flex; flex-wrap: wrap; gap: .25rem 1.1rem; margin: .55rem 0 0; font: 400 .7rem/1.4 var(--k-mono); color: var(--k-soft); }
.bi4-key b { display: inline-block; min-width: 1.3rem; text-align: center; margin-right: .3rem; font-size: .85rem; }
.bi4-key .g-flip { color: var(--k-m-text); background: var(--k-m-tint); border: 1px solid var(--k-m); }
.bi4-key .g-sign { color: var(--k-ink); border: 1px solid var(--k-rule); }
.bi4-key .g-car { color: var(--k-no); border: 2px solid var(--k-no); }
.bi4-small { margin: .5rem 0 0; font-size: .8rem; line-height: 1.38; color: var(--k-soft); max-width: 40rem; }
.bi4-com { border-collapse: collapse; font: 400 .74rem/1.35 var(--k-mono); color: var(--k-ink); width: 100%; }
.bi4-com th { font-size: .6rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--k-soft); padding: .25rem .4rem; text-align: left; }
.bi4-com tbody th { color: var(--k-ink); white-space: nowrap; }
.bi4-com td { padding: .45rem .55rem; border: 1px solid var(--k-rule); vertical-align: top; }
.bi4-com td b { display: block; font-size: .8rem; margin-bottom: .15rem; }
.bi4-com td span { display: block; color: var(--k-soft); font-size: .68rem; }
.bi4-com td.yes { border-left: 4px solid var(--k-ok); } .bi4-com td.yes b { color: var(--k-ok); }
.bi4-com td.no { border-left: 4px solid var(--k-no); } .bi4-com td.no b { color: var(--k-no); }
@container (max-width: 30rem) { .bi4-com tbody th { white-space: normal; width: 4.5rem; padding-left: 0; } .bi4-com td { padding: .4rem .35rem; } }
@container (max-width: 19rem) { .bi4-com tbody th { width: 3.6rem; } .bi4-com td { padding: .4rem .3rem; } }
@container (max-width: 17rem) { .bi4-com tbody th { width: 3rem; } .bi4-com td { padding: .4rem .25rem; } .bi4-com td b { font-size: .7rem; } }
.bi4-cost { margin-top: 1rem; padding-top: .8rem; border-top: 1px solid var(--k-rule); }
.bi4-cgrid { display: grid; grid-template-columns: minmax(14rem, 1fr) minmax(0, 1.4fr); gap: 1rem clamp(1rem, 2.5vw, 2rem); align-items: start; margin-top: .7rem; }
.bi4-big { margin: .3rem 0 .1rem; font-family: var(--k-display); font-weight: 860; font-size: clamp(2rem, 4vw, 2.8rem); line-height: .9; letter-spacing: -.04em; color: var(--k-ink); font-variant-numeric: tabular-nums lining-nums; }
.bi4[data-sign="on"] .bi4-big { color: var(--k-no); }
.bi4-words { margin: .4rem 0 0; font-size: .9rem; line-height: 1.36; color: var(--k-ink); }
.bi4-tabs { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: .8rem 1.2rem; min-width: 0; }
.bi4-tabs .bi4-label { margin-bottom: .3rem; font-size: .62rem; color: var(--k-ink); }
.bi4-jt { width: 100%; border-collapse: collapse; font: 400 .74rem/1.3 var(--k-mono); color: var(--k-ink); font-variant-numeric: tabular-nums; }
.bi4-jt th, .bi4-jt td { padding: .3rem .4rem; text-align: right; border-bottom: 1px solid var(--k-rule); white-space: nowrap; }
.bi4-jt thead th { font-size: .58rem; font-weight: 700; letter-spacing: .05em; text-transform: uppercase; color: var(--k-soft); white-space: normal; vertical-align: bottom; }
.bi4-jt tbody th { text-align: left; font-size: .66rem; color: var(--k-soft); }
.bi4-jt .own { font-weight: 700; border-left: 2px solid var(--k-ink); }
.bi4-s { margin: .8rem 0 0; font-size: .86rem; color: var(--k-soft); max-width: 48rem; }
.bi4-s b { color: var(--k-ink); font-variant-numeric: tabular-nums; }
.bi4-caption { margin: .9rem 0 0; padding-top: .8rem; border-top: 1px solid var(--k-rule); font-size: .92rem; color: var(--k-body); max-width: 52rem; }
.bi4-sr { position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0; }
@container (max-width: 52rem) { .bi4-grid { grid-template-columns: minmax(0, 1fr); } .bi4-cgrid { grid-template-columns: minmax(0, 1fr); } }
@container (max-width: 30rem) { .bi4-tabs { grid-template-columns: minmax(0, 1fr); } .bi4-str td { width: 1.85rem; height: 1.9rem; font-size: .95rem; } .bi4-str tbody th { font-size: .62rem; padding-right: .4rem; white-space: normal; max-width: 6.5rem; } }
@media (forced-colors: active) {
  .bi4 { border-color: CanvasText; }
  .bi4-str td.flip, .bi4-key .g-flip { background: Canvas; color: Highlight; border-color: Highlight; }
  .bi4-str td.car, .bi4-key .g-car { outline-color: Highlight; color: Highlight; border-color: Highlight; }
  .bi4-com td.yes, .bi4-com td.no { border-left-color: CanvasText; }
  .bi4-seg button[aria-pressed="true"] { forced-color-adjust: none; background: Highlight; color: HighlightText; }
}
@media print {
  .bi4 { --k-paper: #ffffff; --k-ink: #1d1d1b; --k-body: #2a2926; --k-soft: #3c3a36; --k-hair: #8a8a8a; --k-rule: #d6d4cf;
    --k-c: #009fe3; --k-m: #e6007e; --k-c-text: #0072b5; --k-m-text: #c4006b; --k-m-tint: #fdeef6; --k-ok: #0b7a3e; --k-no: #c8401f; }
  .bi4, .bi4 * { -webkit-print-color-adjust: exact; print-color-adjust: exact; }
}
@container (max-width: 16rem) { .bi4-big { font-size: 1.5rem; } }