.bk-scope{--page:#fff;--subtle:#f8f8f8;--line:#e0e0e0;--line-soft:#e9e9e9;--ink:#060505;--ink-2:#1a1b1e;--muted:#717784;--faint:#878787;--navy:#10141c;--navy-2:#151a25;--navy-line:#2c2e33;--on-navy:#fff;--on-navy-muted:#afafaf;--brand:#7cc4f5;--brand-deep:#0f6790;--brand-tint:#e8f5fc;--brand-tint-2:#a9dbf3;--sky:#0c8ce9;--sky-tint:#ebfaff;--lime:#93d333;--lime-edge:#5e9a1c;--lime-ink:#22380b;--lime-tint:#eef8da;--amber-tint:#fff5e6;--amber-edge:#dcae05;--amber-ink:#642a03;--red-tint:#fce8ec;--red-edge:#e54967;--red-ink:#7b0f24;--opt:#ededed;--opt-edge:#ccc;--sel:#a5e8fe;--sel-edge:#36bbe5;--ok:#f0fdf4;--ok-edge:#36b289;--bad:#ffd5d5;--bad-edge:#e54967;--ledge:#c3deee;--r-s:8px;--r-m:12px;--r-l:16px;--r-card:20px;--r-sheet:24px;--shadow-card:0 1px 2px #0605050a, 0 8px 24px #0605050f;background:var(--page);height:100dvh;color:var(--ink);font:400 16px/1.6 var(--font-body), Inter, system-ui, -apple-system, "Segoe UI", sans-serif;-webkit-font-smoothing:antialiased;transition:filter .25s;display:flex;overflow:hidden}.bk-scope *,.bk-scope :before,.bk-scope :after{box-sizing:border-box}.bk-frame{flex:1;grid-template-rows:minmax(0,1fr);grid-template-columns:286px 1fr;min-width:0;min-height:0;display:grid}.bk-scope a{color:var(--brand);text-decoration:none}.bk-scope a.bk-chapter-row,.bk-scope a.bk-chapter{color:var(--ink)}.bk-scope a.bk-btn{color:var(--b-ink)}.bk-scope h1,.bk-scope h2,.bk-scope h3,.bk-scope h4{text-wrap:balance;letter-spacing:-.01em;margin:0;font-family:inherit}.bk-scope button,.bk-scope input,.bk-scope textarea{font-family:inherit}.bk-scope input[type=text],.bk-scope textarea{color:var(--ink);background:#fff}.bk-scope img{max-width:100%}.bk-scope--dimmed .bk-side,.bk-scope--dimmed .bk-main{filter:blur(6px)}.bk-eyebrow{letter-spacing:.08em;text-transform:uppercase;color:var(--brand);font-size:12px;font-weight:700}.bk-eyebrow--mute{color:var(--muted)}.bk-tab{font-variant-numeric:tabular-nums}.bk-side{color:var(--ink);scrollbar-width:none;border-right:1px solid var(--line-soft);background:#fff;flex-direction:column;gap:2px;min-height:0;padding:14px 12px 24px;transition:filter .25s;display:flex;overflow-y:auto;box-shadow:inset -14px 0 18px -16px #0605051f}.bk-side::-webkit-scrollbar{display:none}.bk-side-head{align-items:center;padding:0 2px 8px;display:flex}.bk-bare{width:40px;height:40px;color:var(--ink);cursor:pointer;background:0 0;border:0;border-radius:10px;place-items:center;padding:0;display:inline-grid}.bk-bare svg{width:24px;height:24px}.bk-bare:hover{background:var(--subtle)}.bk-bare:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.bk-brand{border-bottom:1px solid var(--line-soft);color:var(--ink);text-align:left;cursor:pointer;width:100%;font:inherit;background:0 0;border-top:0;border-left:0;border-right:0;border-radius:12px;align-items:center;gap:12px;margin-bottom:4px;padding:6px 6px 16px;display:flex}.bk-brand:hover{background:var(--subtle)}.bk-brand-mascot{flex:none;place-items:center;width:44px;height:44px;display:grid}.bk-brand-mascot img{-o-object-fit:contain;object-fit:contain;width:44px;height:44px}.bk-brand-text{flex-direction:column;min-width:0;display:flex}.bk-brand-title{letter-spacing:-.01em;font-size:17px;font-weight:700;line-height:1.2}.bk-brand-sub{color:var(--muted);margin-top:1px;font-size:11.5px;font-weight:600;line-height:1.3}.bk-side-label{letter-spacing:.08em;text-transform:uppercase;color:var(--muted);padding:12px 10px 6px;font-size:12px;font-weight:700}.bk-chapter-row{cursor:pointer;text-align:left;width:100%;color:var(--ink);background:0 0;border:0;border-radius:12px;align-items:center;gap:10px;padding:10px;font-family:inherit;font-size:14.5px;font-weight:700;line-height:1.3;display:flex}.bk-chapter-row:hover{background:var(--subtle)}.bk-chapter-num{background:var(--amber-tint);border-radius:9px;flex:none;place-items:center;width:26px;height:26px;font-size:14px;display:grid}.bk-chapter-num img{-o-object-fit:contain;object-fit:contain;width:18px;height:18px;display:block}.bk-chapter-label{white-space:nowrap;text-overflow:ellipsis;flex:1;min-width:0;overflow:hidden}.bk-chapter-count{color:var(--muted);background:var(--subtle);border:1px solid var(--line-soft);border-radius:999px;padding:2px 8px;font-size:11.5px;font-weight:700}.bk-chapter-caret{color:var(--muted);font-size:10px;transition:transform .2s}.bk-chapter-caret--open{transform:rotate(90deg)}.bk-lessons{border-left:2px solid var(--line-soft);flex-direction:column;gap:2px;margin:0 0 6px 22px;padding:2px 0 8px 8px;display:flex}.bk-nav-item{width:100%;color:var(--ink);cursor:pointer;text-align:left;background:0 0;border:0;border-radius:12px;align-items:center;gap:10px;padding:8px 10px;font-family:inherit;font-size:14px;line-height:1.35;display:flex;position:relative}.bk-nav-item:hover{background:var(--subtle)}.bk-nav-item--active{background:var(--brand-tint);color:var(--brand-deep);font-weight:700}.bk-nav-icon{border:1px solid var(--line-soft);background:#fff;border-radius:8px;flex:none;place-items:center;width:24px;height:24px;font-size:12px;display:grid}.bk-nav-icon img{-o-object-fit:contain;object-fit:contain;width:15px;height:15px;display:block}.bk-nav-item--active .bk-nav-icon{border-color:var(--brand-tint-2)}.bk-nav-num{color:var(--muted);flex:none;width:26px;font-size:10.5px;font-weight:700}.bk-nav-item--active .bk-nav-num{color:var(--brand-deep)}.bk-nav-main{flex-direction:column;flex:1;gap:4px;min-width:0;display:flex}.bk-nav-title{text-overflow:ellipsis;white-space:nowrap;overflow:hidden}.bk-nav-title small{color:var(--muted);text-transform:uppercase;letter-spacing:.04em;margin-left:6px;font-size:10.5px;font-weight:600}.bk-nav-bar{background:var(--line-soft);border-radius:999px;height:4px;display:block;overflow:hidden}.bk-nav-bar i{background:var(--lime);border-radius:999px;height:100%;display:block}.bk-nav-tick{background:var(--lime);width:18px;height:18px;color:var(--lime-ink);border-radius:999px;flex:none;place-items:center;font-size:10px;font-weight:800;display:grid}.bk-nav-pct{color:var(--brand-deep);font-variant-numeric:tabular-nums;font-size:11px;font-weight:700}.bk-scope--rail .bk-frame{grid-template-columns:64px 1fr}.bk-scope--rail .bk-side{padding:14px 8px;overflow:hidden}.bk-scope--rail .bk-side>:not(.bk-side-head){display:none}.bk-scope--rail .bk-side-head{justify-content:center}.bk-scope--rail .bk-side-toggle svg{transform:scaleX(-1)}.bk-main{perspective:1800px;flex-direction:column;min-width:0;min-height:0;transition:filter .25s;display:flex;position:relative}.bk-topbar{z-index:5;-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);border-bottom:1px solid var(--line-soft);background:#ffffffeb;flex:none;align-items:center;gap:12px;padding:10px 24px;display:flex}.bk-track{background:var(--line-soft);border-radius:999px;flex:1;height:8px;overflow:hidden}.bk-track i{background:var(--lime);border-radius:999px;height:100%;transition:width .3s;display:block}.bk-topbar-t{color:var(--muted);white-space:nowrap;font-size:13px;font-weight:600}.bk-icon-btn{width:40px;height:40px;color:var(--ink-2);cursor:pointer;background:0 0;border:0;border-radius:10px;flex:none;place-items:center;padding:0;display:inline-grid}.bk-close-btn{z-index:1;position:relative}.bk-icon-btn:hover{background:var(--subtle)}.bk-icon-btn[aria-pressed=true]{background:var(--brand-tint);color:var(--brand-deep)}.bk-icon-btn svg{width:22px;height:22px}.bk-icon-btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.bk-menu-btn{display:none}.bk-page{transform-origin:0;backface-visibility:hidden;-webkit-overflow-scrolling:touch;flex:1;min-height:0;position:relative;overflow:hidden auto}.bk-spread{max-width:1100px;margin:0 auto;padding:28px 62px 72px}.bk-foot{border-top:1px solid var(--line-soft);color:var(--muted);background:#fff;flex:none;justify-content:space-between;align-items:center;gap:12px;padding:8px 24px;font-size:12.5px;display:flex}.bk-foot-page{color:var(--ink-2);font-variant-numeric:tabular-nums;font-weight:700}.bk-turn{border:1px solid var(--ledge);width:44px;height:64px;box-shadow:0 4px 0 var(--ledge);color:var(--ink-2);cursor:pointer;z-index:4;background:#fff;border-radius:14px;place-items:center;font-size:26px;line-height:1;display:grid;position:absolute;top:50%;transform:translateY(-50%)}.bk-turn:active{box-shadow:0 1px 0 var(--ledge);transform:translateY(calc(3px - 50%))}.bk-turn:disabled{opacity:0;pointer-events:none}.bk-turn--prev{left:10px}.bk-turn--next{right:10px}@media (hover:none) and (pointer:coarse){.bk-turn{display:none}}.bk-page--turn-next{animation:.42s cubic-bezier(.4,0,.6,1) forwards bk-fold-next}.bk-page--turn-prev{animation:.42s cubic-bezier(.4,0,.6,1) forwards bk-fold-prev}.bk-page--land-next{animation:.38s cubic-bezier(.2,.7,.2,1) both bk-land-next}.bk-page--land-prev{animation:.38s cubic-bezier(.2,.7,.2,1) both bk-land-prev}@keyframes bk-fold-next{to{opacity:.35;transform:rotateY(-78deg)}}@keyframes bk-fold-prev{to{opacity:.35;transform:rotateY(78deg)translate(-8%)}}@keyframes bk-land-next{0%{opacity:0;transform:rotateY(60deg)translate(10%)}to{opacity:1;transform:none}}@keyframes bk-land-prev{0%{opacity:0;transform:rotateY(-60deg)}to{opacity:1;transform:none}}.bk-page--turn-next:after,.bk-page--turn-prev:after{content:"";pointer-events:none;background:linear-gradient(90deg,#0605052e,#0000 40%);position:absolute;inset:0}@media (prefers-reduced-motion:reduce){.bk-page--turn-next,.bk-page--turn-prev,.bk-page--land-next,.bk-page--land-prev{animation:none}}.bk-btn{border-radius:var(--r-m);cursor:pointer;height:48px;color:var(--b-ink);background:var(--b-face);box-shadow:0 4px 0 var(--b-edge);border:0;justify-content:center;align-items:center;gap:8px;margin-bottom:4px;padding:0 20px;font-family:inherit;font-size:15px;font-weight:600;text-decoration:none;display:inline-flex}.bk-btn--sm{height:38px;box-shadow:0 3px 0 var(--b-edge);margin-bottom:3px;padding:0 14px;font-size:14px}.bk-btn--primary{--b-face:var(--lime);--b-edge:var(--lime-edge);--b-ink:var(--lime-ink)}.bk-btn--navy{--b-face:var(--navy);--b-edge:#000;--b-ink:#fff}.bk-btn--tertiary{--b-face:#fff;--b-edge:var(--ledge);--b-ink:var(--ink);border:1px solid var(--ledge)}.bk-btn:active{box-shadow:0 1px 0 var(--b-edge);transform:translateY(3px)}.bk-btn:disabled{--b-face:#e4e7ec;--b-edge:#cfd4dc;--b-ink:#98a2b3;cursor:default}.bk-btn:disabled:active{box-shadow:0 4px 0 var(--b-edge);transform:none}.bk-btn:focus-visible{outline:2px solid var(--b-edge);outline-offset:2px}.bk-pill{background:var(--brand-tint);height:26px;color:var(--brand-deep);border-radius:999px;align-items:center;gap:6px;padding:0 10px;font-size:12.5px;font-weight:600;display:inline-flex}.bk-pill--grey{background:var(--subtle);color:var(--muted)}.bk-lesson-head{border-bottom:2px solid var(--navy);margin-bottom:8px;padding-bottom:22px}.bk-lesson-head-row{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:20px;display:flex}.bk-h1{text-wrap:pretty;letter-spacing:-.02em;color:var(--brand-deep);margin:8px 0 12px;font-size:clamp(30px,4vw,40px);font-weight:800;line-height:1.15}.bk-hook{color:var(--ink-2);max-width:56ch;margin:0;font-size:18px;line-height:1.55}.bk-hook b{color:var(--brand)}.bk-planned{color:var(--muted);margin:10px 0 0;font-size:14px}.bk-video-tile{background:var(--navy);color:#fff;cursor:pointer;text-align:left;font:inherit;border:0;border-radius:14px;flex:none;grid-template-columns:40px 1fr;align-items:center;gap:12px;max-width:320px;margin-bottom:5px;padding:8px 14px 8px 8px;display:grid;box-shadow:0 5px #000}.bk-video-tile:active{transform:translateY(4px);box-shadow:0 1px #000}.bk-video-tile:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.bk-video-tile .bk-video-play,.bk-tile-play{background:var(--lime);width:40px;height:40px;box-shadow:0 3px 0 var(--lime-edge);color:var(--lime-ink);border-radius:50%;place-items:center;display:grid}.bk-video-play svg{width:20px;height:20px}.bk-video-tile b{font-size:14px;line-height:1.3;display:block}.bk-video-tile span{color:var(--on-navy-muted);font-size:12px}.bk-quote{border-radius:var(--r-l);background:var(--navy);color:#fff;grid-template-columns:auto 1fr;align-items:start;gap:12px;margin:18px 0 0;padding:16px 20px;font-size:16.5px;font-weight:600;display:grid}.bk-quote-mark{color:var(--lime);font-size:22px;line-height:1}.bk-reader{background:var(--subtle);color:var(--ink-2);border-radius:14px;flex-wrap:wrap;align-items:center;gap:14px;margin:18px 0 6px;padding:12px 16px;font-size:13.5px;display:flex}.bk-reader b{color:var(--ink)}.bk-reader-sep{color:var(--faint)}.bk-reader-why{color:var(--brand);cursor:pointer;font:inherit;background:0 0;border:0;margin-left:auto;padding:0;font-weight:600}.bk-reader-note{color:var(--muted);margin:0 0 6px;padding:10px 16px;font-size:13.5px}.bk-sec{padding:30px 0 10px;display:block}.bk-sec:after{content:"";clear:both;display:block}.bk-sec+.bk-sec{border-top:1px solid var(--line-soft)}.bk-sec-num{flex-wrap:wrap;align-items:baseline;gap:14px;margin-bottom:10px;display:flex}.bk-sec-num b{color:#fff;background:var(--navy);letter-spacing:.04em;font-variant-numeric:tabular-nums;border-radius:8px;padding:3px 9px;font-size:13px;font-weight:800}.bk-h2{letter-spacing:-.015em;color:var(--brand);font-size:26px;font-weight:800;line-height:1.2}.bk-sec-icon{-o-object-fit:contain;object-fit:contain;align-self:center;width:34px;height:34px;margin-left:auto}.bk-practical{letter-spacing:.06em;text-transform:uppercase;color:var(--lime-ink);background:var(--lime-tint);border-radius:999px;padding:4px 10px;font-size:11.5px;font-weight:800}.bk-question{color:var(--ink-2);margin:0 0 14px;font-size:17px;font-style:italic}.bk-prose{min-width:0;max-width:100%}.bk-prose p,.bk-body{margin:0 0 16px;font-size:17px;line-height:1.72}.bk-hl{color:inherit;background:0 0}.bk-hl--term{color:var(--brand);border-bottom:2px solid var(--brand-tint-2);font-weight:700}.bk-hl--fact{background:var(--lime-tint);-webkit-box-decoration-break:clone;box-decoration-break:clone;border-radius:4px;padding:0 3px;font-weight:600}.bk-hl--value{color:var(--brand-deep);font-variant-numeric:tabular-nums;font-weight:700}.bk-hl--warn{color:var(--red-ink);font-weight:700}.bk-scope .katex{font-size:1.05em;line-height:inherit}.bk-scope .katex-display{margin:0;padding:2px 0;overflow:auto hidden}.bk-tex-display{margin:8px 0;display:block}.bk-scope .katex .katex-error{color:var(--red-ink)}.bk-depth{border:1px solid var(--ledge);box-shadow:0 4px 0 var(--ledge);background:#fff;border-radius:14px;gap:4px;margin:0 0 18px;padding:4px;display:inline-flex}.bk-depth button{height:36px;color:var(--ink-2);cursor:pointer;background:0 0;border:0;border-radius:10px;align-items:center;gap:8px;padding:0 14px;font-family:inherit;font-size:13.5px;font-weight:600;display:inline-flex}.bk-depth button svg{width:18px;height:18px}.bk-depth button[aria-selected=true]{background:var(--navy);color:#fff}.bk-depth button:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.bk-depth-hint{color:var(--muted);margin:-10px 0 18px;font-size:12.5px}.bk-depth-hint b{color:var(--brand)}.bk-mnote{float:right;clear:right;color:#1a1b1e;background:var(--m-paper);border-radius:4px;width:300px;margin:6px 0 18px 28px;padding:26px 16px 16px;font-size:14px;line-height:1.5;position:relative;transform:rotate(-1.4deg);box-shadow:0 6px 14px #0605051f,0 1px 2px #06050514}.bk-mnote--even{transform:rotate(1.1deg)}.bk-mnote:before{content:"";background:#ffffff8c;border:1px solid #0605050f;border-radius:2px;width:76px;height:20px;margin-left:-38px;position:absolute;top:-8px;left:50%;transform:rotate(-2deg)}.bk-mnote:after{content:"";background:linear-gradient(135deg,#0000 50%,#0605051a 50%);border-bottom-right-radius:4px;width:22px;height:22px;position:absolute;bottom:0;right:0}.bk-mnote-lbl{letter-spacing:.08em;text-transform:uppercase;color:var(--m-ink);align-items:center;gap:8px;margin-bottom:6px;font-size:11.5px;font-weight:800;display:flex}.bk-mnote-lbl svg{width:20px;height:20px}.bk-mnote--idea{--m-paper:#bfe6ff;--m-ink:#0a4a6e}.bk-mnote--tip{--m-paper:#fff08a;--m-ink:#6b4a00}.bk-mnote--watch{--m-paper:#ffc2d1;--m-ink:#8e1030}.bk-mnote--remember{--m-paper:#c8f5c4;--m-ink:#245c1e}.bk-mnote--link{--m-paper:#e4d4ff;--m-ink:#4b2c8c}.bk-mnote--pinned{float:none;clear:both;width:auto;margin:0 0 18px;transform:none;box-shadow:0 8px 18px #8e10302e,0 1px 2px #06050514}.bk-mnote--pinned:before{width:96px;margin-left:-48px}.bk-mnote--wide{float:none;clear:both;width:auto;margin:0 0 18px;font-size:14.5px;transform:none}.bk-defn{clear:both;border-left:4px solid var(--navy);background:var(--subtle);border-radius:0 12px 12px 0;margin:6px 0 20px;padding:14px 18px}.bk-defn-lbl{letter-spacing:.08em;text-transform:uppercase;color:var(--brand);margin-bottom:4px;font-size:11.5px;font-weight:800}.bk-defn p{margin:0;font-size:17px;font-weight:600;line-height:1.5}.bk-wonder{clear:both;border-radius:var(--r-l);color:#fff;background:#0a2540;border:1px solid #0a2540;grid-template-columns:36px 1fr;gap:12px;margin:0 0 18px;padding:16px 18px;display:grid}.bk-wonder-ico{width:36px;height:36px;display:block}.bk-wonder-lbl{letter-spacing:.06em;text-transform:uppercase;color:#7cc4f5;margin-bottom:2px;font-size:12px;font-weight:700}.bk-wonder p{color:#fff;margin:0;font-size:15.5px;line-height:1.6}.bk-wonder-working{color:#d5e3ee;border-top:1px dashed #7cc4f573;margin-top:8px;padding-top:8px;font-size:14px}.bk-wonder-source{color:#9fb3c4;overflow-wrap:anywhere;margin-top:4px;font-size:12.5px;display:block}.bk-wonder>div{min-width:0}.bk-wonder-working{-webkit-overflow-scrolling:touch;min-width:0;max-width:100%;overflow:auto hidden}.bk-wonder-working .katex{max-width:100%;display:inline-block}.bk-wonder a{color:#7cc4f5}.bk-eqline{clear:both;flex-wrap:wrap;align-items:center;gap:22px;margin:4px 0 18px;display:flex}.bk-eqline-f{background:var(--brand-tint);font-variant-numeric:tabular-nums;border-radius:12px;padding:10px 22px;font-size:26px;font-weight:700}.bk-eqline-k{color:var(--ink-2);flex-wrap:wrap;gap:16px;font-size:14.5px;display:flex}.bk-eqline-k b{color:var(--sym);font-size:16px}.bk-eqline-k em{color:var(--muted);margin-left:4px;font-style:normal}.bk-wex{clear:both;border-top:2px solid var(--navy);margin:0 0 20px}.bk-wex-q{padding:10px 0 6px;font-size:15.5px;font-weight:700}.bk-wex-q span{color:var(--brand);letter-spacing:.08em;text-transform:uppercase;margin-right:10px;font-size:11.5px;font-weight:800}.bk-wex ol{counter-reset:w;gap:6px;margin:0;padding:0 0 10px;list-style:none;display:grid}.bk-wex li{border-top:1px solid var(--line-soft);padding:6px 0 6px 30px;font-size:15.5px;line-height:1.55;position:relative}.bk-wex li:before{counter-increment:w;content:counter(w);color:var(--brand);font-weight:800;position:absolute;top:6px;left:0}.bk-figure{clear:both;margin:12px 0 26px;display:block}.bk-figure img{border-radius:12px;width:100%;height:auto;display:block}.bk-figure-cap{color:var(--ink-2);margin-top:10px;font-size:14.5px;line-height:1.55}.bk-figure-cap b{color:var(--brand);letter-spacing:.06em;text-transform:uppercase;margin-bottom:4px;font-size:12px;display:block}.bk-figure-credit{color:var(--muted);margin-top:6px;font-size:12px;display:block}.bk-figure--side{clear:right;float:right;width:300px;max-width:40%;margin:4px 0 18px 28px}.bk-sec--side-fig 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var(--brand);outline-offset:2px;border-color:var(--brand)}.bk-numq--correct input{border-color:var(--ok-edge);background:var(--ok)}.bk-numq--wrong input{border-color:var(--bad-edge);background:var(--bad)}.bk-numq-unit{color:var(--muted);font-weight:600}.bk-blank-text{margin-bottom:12px;font-size:17px;line-height:2.1}.bk-slot{border:2px dashed var(--opt-edge);background:var(--subtle);min-width:96px;height:34px;color:var(--ink);vertical-align:middle;cursor:pointer;border-radius:10px;margin:0 4px;padding:0 10px;font-family:inherit;font-size:15px;font-weight:600;line-height:30px;display:inline-block}.bk-slot--filled{background:var(--sel);border-style:solid;border-color:var(--sel-edge)}.bk-slot--correct{background:var(--ok);border-style:solid;border-color:var(--ok-edge)}.bk-slot--wrong{background:var(--bad);border-style:solid;border-color:var(--bad-edge)}.bk-bank{flex-wrap:wrap;gap:8px;margin-bottom:14px;display:flex}.bk-word{border:2px solid 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12px;font-size:17px;line-height:1.55}.bk-xp-meta{color:#1a1b1e;justify-content:space-between;align-items:baseline;gap:16px;margin-bottom:14px;font-size:15.5px;display:flex}.bk-xp-meta b{white-space:nowrap;font-weight:600}.bk-xp-opts{gap:10px;display:grid}.bk-xp-opt{text-align:left;width:100%;font:inherit;color:#1a1b1e;cursor:pointer;background:#fff;border:1.5px solid #e6e8ec;border-radius:10px;grid-template-columns:22px 1fr;align-items:center;gap:14px;padding:13px 18px;font-size:15.5px;font-weight:600;transition:border-color .12s,background .12s,transform 60ms;display:grid;box-shadow:0 3px #eef0f3}.bk-xp-opt:hover:not(:disabled){border-color:#7cc4f5}.bk-xp-opt:active:not(:disabled){transform:translateY(2px);box-shadow:0 1px #eef0f3}.bk-xp-opt:focus-visible{outline-offset:2px;outline:2px solid #3b8ed0}.bk-xp-letter{color:#8a93a0;font-size:16px;font-weight:500}.bk-xp-opt--picked{background:#eaf6fe;border-color:#7cc4f5;box-shadow:0 3px 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var(--line);border-radius:14px;flex-wrap:wrap;gap:8px;padding:12px;display:flex}.bk-ib-slot{border:2px dashed var(--line);border-radius:12px;flex-direction:column;justify-content:center;gap:4px;min-height:48px;padding:4px;display:flex}.bk-ib-slot--ready{border-color:var(--sel-edge);cursor:pointer;background:#f3fbff}.bk-ib-hint{color:var(--faint);padding:0 8px;font-size:13px}.bk-ib-fix{color:var(--ok-edge);padding:0 6px;font-size:13px;font-weight:600}.bk-ib-rows{gap:10px;display:grid}.bk-ib-row{grid-template-columns:minmax(120px,.8fr) 1.2fr;align-items:center;gap:12px;display:grid}.bk-ib-left{font-size:15px;font-weight:700}.bk-ib-left .katex{font-size:1.3em}.bk-ib-groups{grid-template-columns:repeat(var(--bk-ib-cols,2), 1fr);gap:12px;display:grid}.bk-ib-group{border:2px dashed 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