.bs{--bs-ink:#243947;--bs-muted:#526b76;--bs-paper:#fff;--bs-soft:#eef6f8;--bs-line:#bdd4da;--bs-accent:#087a83;max-width:1260px;margin:auto;padding:28px 24px 50px;color:var(--bs-ink);font-family:Inter,Arial,sans-serif;line-height:1.55}.bs *,.bs ::after,.bs ::before{box-sizing:border-box}.bs [hidden]{display:none!important}.bs h1,.bs h2,.bs h3,.bs p{margin:0;color:inherit}.bs h1{font-size:clamp(2rem, 4vw, 3rem);line-height:1.15;margin:8px 0}.bs h2{font-size:1.45rem;margin-bottom:12px}.bs h3{font-size:1.05rem}.bs a{color:var(--bs-accent)}.bs button,.bs input,.bs select{font:inherit}.bs button,.bs select{min-height:44px;padding:9px 13px;border:1px solid var(--bs-line);border-radius:8px;color:var(--bs-ink);background:var(--bs-paper)}.bs button{cursor:pointer;font-weight:700}.bs button:hover{border-color:var(--bs-accent)}.bs :is(button,select,input,summary,a):focus-visible{outline:3px solid #dd8614;outline-offset:3px}.bs-heading{display:flex;align-items:flex-start;justify-content:space-between;gap:20px;margin-bottom:22px}.bs-heading a{display:inline-block;margin-bottom:17px;font-size:.88rem}.bs-heading>div>p:last-child,.bs-subtitle{color:var(--bs-muted)}.bs-eyebrow{color:var(--bs-accent)!important;font-size:.75rem;font-weight:800;letter-spacing:.08em}.bs-intro,.bs-note{margin-bottom:22px;padding:15px 19px;border-left:4px solid var(--bs-accent);border-radius:6px;background:var(--bs-soft)}.bs-print-actions{display:flex;align-items:flex-end;gap:10px;flex-wrap:wrap}.bs-print-actions label{display:flex;flex-direction:column;gap:5px;font-size:.78rem;font-weight:700}.bs-tabs{display:flex;gap:8px;margin-bottom:24px;border-bottom:1px solid var(--bs-line)}.bs-tabs button{border:0;border-bottom:3px solid transparent;border-radius:7px 7px 0 0;background:0 0}.bs-tabs [aria-selected=true]{color:var(--bs-accent);border-bottom-color:var(--bs-accent);background:var(--bs-paper)}.bs [role=tabpanel]{margin-top:20px}.bs-explorer-grid{display:grid;grid-template-columns:minmax(280px,0.9fr) minmax(300px,1.1fr);gap:26px;align-items:start}.bs-brain-figure{margin:0;padding:14px;border:1px solid var(--bs-line);border-radius:14px;background:var(--bs-soft)}.bs-brain-figure img{display:block;width:100%;max-width:100%;height:auto;border-radius:9px}.bs-brain-figure figcaption{margin-top:10px;color:var(--bs-muted);font-size:.86rem}.bs-function-area{padding:22px;border:1px solid var(--bs-line);border-radius:14px}.bs-function-area>p{color:var(--bs-muted)}.bs-function-buttons{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin:18px 0}.bs-function-buttons button[aria-pressed=true]{color:#fff;border-color:var(--bs-accent);background:var(--bs-accent)}.bs-function-detail{min-height:142px;padding:15px;border-radius:9px;background:var(--bs-soft)}.bs-function-detail p{margin-top:8px}.bs-card{margin:18px 0;padding:22px;border:1px solid var(--bs-line);border-radius:14px;background:var(--bs-paper)}.bs-illusion{display:grid;grid-template-columns:repeat(2,minmax(0,140px));justify-content:center;gap:clamp(8px,9vw,120px);padding:28px 8px;margin:22px 0 16px;overflow:hidden;border-radius:12px;background:#f7fafb}.bs-illusion-set{position:relative;width:140px;height:140px}.bs-center-circle,.bs-neighbour{position:absolute;display:block;border:2px solid #304d59;border-radius:50%;background:#61b6bd}.bs-center-circle{z-index:2;top:54px;left:54px;width:32px;height:32px}.bs-small-neighbours .bs-neighbour{width:12px;height:12px;background:#f2b84a}.bs-small-neighbours .bs-neighbour:nth-of-type(2){top:6px;left:64px}.bs-small-neighbours .bs-neighbour:nth-of-type(3){top:22px;left:106px}.bs-small-neighbours .bs-neighbour:nth-of-type(4){top:64px;left:122px}.bs-small-neighbours .bs-neighbour:nth-of-type(5){top:106px;left:106px}.bs-small-neighbours .bs-neighbour:nth-of-type(6){top:122px;left:64px}.bs-small-neighbours .bs-neighbour:nth-of-type(7){top:106px;left:22px}.bs-small-neighbours .bs-neighbour:nth-of-type(8){top:64px;left:6px}.bs-small-neighbours .bs-neighbour:nth-of-type(9){top:22px;left:22px}.bs-large-neighbours .bs-neighbour{width:40px;height:40px;background:#ed925d}.bs-large-neighbours .bs-neighbour:nth-of-type(2){top:0;left:50px}.bs-large-neighbours .bs-neighbour:nth-of-type(3){top:10px;left:90px}.bs-large-neighbours .bs-neighbour:nth-of-type(4){top:50px;left:100px}.bs-large-neighbours .bs-neighbour:nth-of-type(5){top:90px;left:90px}.bs-large-neighbours .bs-neighbour:nth-of-type(6){top:100px;left:50px}.bs-large-neighbours .bs-neighbour:nth-of-type(7){top:90px;left:10px}.bs-large-neighbours .bs-neighbour:nth-of-type(8){top:50px;left:0}.bs-large-neighbours .bs-neighbour:nth-of-type(9){top:10px;left:10px}.bs-illusion[data-revealed=true] .bs-neighbour{display:none}.bs-actions{display:flex;flex-wrap:wrap;gap:10px}.bs-primary{color:#fff!important;border-color:var(--bs-accent)!important;background:var(--bs-accent)!important}#bs-illusion-feedback{margin-top:12px;font-weight:700}.bs-question fieldset{min-width:0;margin:0 0 16px;padding:0;border:0}.bs-question legend{font-size:1.05rem;font-weight:800}.bs-option{display:flex;align-items:flex-start;gap:11px;margin-top:10px;padding:11px;border:1px solid var(--bs-line);border-radius:8px;cursor:pointer}.bs-option input{width:18px;height:18px;margin-top:3px;accent-color:var(--bs-accent)}.bs-option:has(input:checked){border-color:var(--bs-accent);background:var(--bs-soft)}.bs-question-feedback{margin-top:11px}.bs-question-feedback[data-state]{padding:11px;border-radius:6px}.bs-question-feedback[data-state=correct]{color:#145237;border-left:3px solid #287956;background:#e5f5eb}.bs-question-feedback[data-state=retry]{color:#70430b;border-left:3px solid #ad7017;background:#fff3dc}.bs-strategies{margin-top:26px;padding:22px;border-radius:14px;background:var(--bs-soft)}.bs-strategies>div{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.bs-strategies article{padding:15px;border:1px solid var(--bs-line);border-radius:9px;background:var(--bs-paper)}.bs-strategies p{margin-top:7px;color:var(--bs-muted)}.bs-reference{margin-top:24px;padding-top:10px;border-top:1px solid var(--bs-line)}.bs-reference summary{min-height:44px;padding:9px 0;color:var(--bs-accent);font-weight:800;cursor:pointer}.bs-print{display:none}[data-theme=dark] .bs{--bs-ink:#e6eff1;--bs-muted:#bacbd0;--bs-paper:#19313b;--bs-soft:#122730;--bs-line:#46616b;--bs-accent:#76d2d0}[data-theme=dark] .bs-illusion{background:#11262f}@media screen and (max-width:800px){.bs-explorer-grid,.bs-heading{grid-template-columns:1fr;flex-direction:column}.bs-explorer-grid{display:grid}.bs-strategies>div{grid-template-columns:1fr}}@media screen and (max-width:520px){.bs{padding:20px 12px 35px}.bs-tabs{gap:0}.bs-tabs button{flex:1;padding:10px 4px;font-size:.72rem}.bs-function-buttons{grid-template-columns:1fr}.bs-card,.bs-function-area,.bs-strategies{padding:17px}.bs-illusion{gap:8px}}@media print{@page{size:A4 portrait;margin:12mm}#main-content,.bs,body,html{width:auto!important;max-width:none!important;margin:0!important;padding:0!important;color:#111!important;background:#fff!important}#main-content>:not(.bs),.bs>:not(.bs-print),body>:not(main):not(script):not(style):not(link){display:none!important}.bs .bs-print{display:block;font:10pt/1.32 Arial,sans-serif}.bs-print h1{margin:0 0 2mm;font-size:21pt}.bs-print h2{margin:4mm 0 2mm;font-size:13pt}.bs-print p{margin:1.5mm 0}.bs-print-question{margin-bottom:3mm;break-inside:avoid}.bs-print-flow{display:flex;align-items:stretch;gap:3px;margin:3mm 0;font-weight:700}.bs-print-flow span{flex:1;min-width:0;padding:2.5mm 1mm;border:1px solid #555;text-align:center;overflow-wrap:anywhere}.bs-print-flow span:not(:last-child)::after{content:'→';float:right;margin-right:-5px}.bs:not([data-print-kind=answer]) .bs-answer,.bs[data-print-kind=answer] .bs-student{display:none!important}.bs .bs-print section{padding:0;min-height:0}}