:root{
  --sidebar-width:340px;--topbar-height:58px;--ink:#162033;--muted:#657386;--line:#d9e2ef;--paper:#fff;--page:#f4f7fb;--blue:#1a4f8b;--blue-dark:#10385f;--blue-soft:#eaf3ff;--green:#267855;--green-soft:#eefaf4;--gold:#996600;--gold-soft:#fff9e8;--red:#963737;--red-soft:#fff2f2;--gray-soft:#f8f8f8;--shadow:0 16px 40px rgba(16,42,67,.12)
}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;color:var(--ink);background:var(--page);font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.65}.book-shell{display:grid;grid-template-columns:var(--sidebar-width) minmax(0,1fr);min-height:100vh}.book-sidebar{position:sticky;top:0;height:100vh;overflow:auto;background:#0f2742;color:#fff;border-right:1px solid rgba(255,255,255,.12);z-index:50}.sidebar-head{padding:22px 20px 16px;border-bottom:1px solid rgba(255,255,255,.12)}.sidebar-title{font-weight:850;font-size:1.18rem}.sidebar-subtitle{margin-top:4px;color:rgba(255,255,255,.72);font-size:.88rem}.sidebar-search{padding:14px 16px;border-bottom:1px solid rgba(255,255,255,.12)}.sidebar-search input{width:100%;border:1px solid rgba(255,255,255,.2);border-radius:10px;padding:10px 12px;outline:none;color:#fff;background:rgba(255,255,255,.08)}.sidebar-search input::placeholder{color:rgba(255,255,255,.6)}.chapter-tree{padding:12px 10px 26px}.home-link{display:block;color:rgba(255,255,255,.9);text-decoration:none;padding:10px 12px;border-radius:10px;font-weight:750}.home-link:hover,.home-link.active{background:rgba(255,255,255,.13)}.chapter-node{margin:4px 0;border-radius:10px}.chapter-node[hidden]{display:none}.chapter-node summary{list-style:none;cursor:pointer;border-radius:10px}.chapter-node summary::-webkit-details-marker{display:none}.chapter-node summary::before{content:"▸";display:inline-block;width:16px;margin-left:2px;color:rgba(255,255,255,.55);transform:translateY(-1px)}.chapter-node[open] summary::before{content:"▾"}.chapter-node summary:hover,.chapter-node summary.active{background:rgba(255,255,255,.13)}.chapter-node summary a{display:inline-grid;grid-template-columns:34px minmax(0,1fr);align-items:start;width:calc(100% - 22px);color:#fff;text-decoration:none;padding:10px 10px 10px 0}.chapter-number{display:inline-flex;align-items:center;justify-content:center;width:26px;height:26px;margin-top:1px;border-radius:999px;background:rgba(255,255,255,.14);font-size:.8rem;font-weight:850}.chapter-name{font-size:.92rem;line-height:1.28}.section-list{margin:2px 0 8px 54px;padding-left:12px;border-left:1px solid rgba(255,255,255,.17)}.section-list a{display:block;color:rgba(255,255,255,.72);text-decoration:none;font-size:.86rem;padding:5px 6px;border-radius:7px}.section-list a:hover,.section-list a.active-section{color:#fff;background:rgba(255,255,255,.1)}.book-topbar{position:sticky;top:0;z-index:30;height:var(--topbar-height);display:flex;align-items:center;gap:12px;padding:0 22px;background:rgba(255,255,255,.94);border-bottom:1px solid var(--line);backdrop-filter:blur(10px)}.sidebar-toggle{display:none;border:1px solid var(--line);background:#fff;border-radius:10px;padding:7px 11px;font-size:1.1rem;cursor:pointer}.topbar-title{min-width:0;flex:1;font-weight:850;color:var(--blue-dark);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.topbar-home{color:var(--blue);text-decoration:none;font-weight:750}.book-main{min-width:0}.reader-page{width:min(1100px,calc(100% - 42px));margin:28px auto 70px;background:var(--paper);border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);padding:36px 42px}.hero{padding:18px 0 30px}.eyebrow{color:var(--green);font-weight:850;text-transform:uppercase;letter-spacing:.08em;font-size:.82rem}.hero h1{font-size:clamp(2rem,4vw,3.2rem);line-height:1.08;margin:0;color:var(--blue-dark)}.lead{font-size:1.12rem;color:var(--muted);max-width:760px}.author{font-weight:850;color:var(--blue)}.chapter-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:14px;margin-top:18px}.chapter-card{display:grid;gap:8px;min-height:120px;padding:18px;text-decoration:none;color:var(--ink);border:1px solid var(--line);border-radius:16px;background:linear-gradient(180deg,#fff,#f8fbff);transition:transform .12s ease,border .12s ease,box-shadow .12s ease}.chapter-card:hover{transform:translateY(-2px);border-color:#b7c9df;box-shadow:0 10px 28px rgba(16,42,67,.12)}.card-number{color:var(--green);font-size:.84rem;font-weight:850;text-transform:uppercase;letter-spacing:.04em}.card-title{font-weight:850;line-height:1.25}.chapter-toolbar{display:flex;justify-content:space-between;gap:16px;margin:-8px 0 26px;padding:12px 0;color:var(--muted);border-bottom:1px solid var(--line)}.chapter-toolbar.bottom{margin:38px 0 0;border-top:1px solid var(--line);border-bottom:0}.chapter-toolbar a{color:var(--blue);font-weight:750;text-decoration:none}.chapter-content{max-width:930px;margin:0 auto}.chapter-content h1{color:var(--blue-dark);font-size:clamp(1.8rem,3vw,2.55rem);line-height:1.1;margin:0 0 28px}.chapter-content h2{margin-top:2.2em;color:var(--blue-dark);border-bottom:1px solid var(--line);padding-bottom:.25em}.chapter-content h3{margin-top:1.7em;color:#213b59}.chapter-content p,.chapter-content li{font-size:1.02rem}.chapter-content a{color:var(--blue)}.smallcaps{font-variant:small-caps}.display-math{margin:1rem 0;overflow-x:auto}.learningbox,.keybox,.warningbox,.summarybox,.theorem-like,.exercise-card,.proof,.algorithm-card,.figure-card{margin:1.15rem 0;padding:1rem 1.1rem;border:1px solid var(--line);border-radius:14px;background:#fbfdff}.learningbox{border-left:5px solid var(--blue);background:var(--blue-soft)}.keybox{border-left:5px solid var(--green);background:var(--green-soft)}.warningbox{border-left:5px solid var(--red);background:var(--red-soft)}.summarybox{border-left:5px solid #555;background:var(--gray-soft)}.theorem-like{border-left:5px solid var(--blue)}.example{border-left-color:var(--green);background:#fcfffd}.definition{border-left-color:#6f4aad;background:#fcfaff}.lemma,.theorem,.proposition,.corollary{background:#fbfdff}.exercise-card{border-left:5px solid var(--gold);background:var(--gold-soft)}.proof{border-left:5px solid #7b8794;background:#fff}.box-title,.theorem-title,.definition-title,.lemma-title,.example-title,.remark-title,.exercise-title,.proof-title,.algorithm-title{font-weight:850;color:var(--blue-dark);margin:0 0 .55rem}.exercise-title{color:#5a3b00}.algorithm-card{border-left:5px solid #334e68;background:#f8fbff}.algorithm-steps{margin:0;padding-left:1.4rem}.alg-end{color:var(--muted)}.figure-card{text-align:center;border-left:5px solid #425a70;background:#fff}.fig-svg{width:min(100%,820px);height:auto;display:block;margin:0 auto}.figure-placeholder{height:180px;border:1px dashed var(--line);display:grid;place-items:center;color:var(--muted)}figcaption{font-size:.94rem;color:var(--muted);margin-top:.55rem;text-align:left}.lab-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:14px}.lab-card{display:grid;gap:6px;padding:16px;border:1px solid var(--line);border-radius:16px;background:linear-gradient(180deg,#fff,#f7fbff);text-decoration:none;color:var(--ink);box-shadow:0 8px 24px rgba(16,42,67,.08)}.lab-card span{font-size:.8rem;text-transform:uppercase;letter-spacing:.06em;color:var(--green);font-weight:850}.lab-card strong{color:var(--blue-dark)}.flip-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:14px}.flip-card{min-height:130px;border:1px solid var(--line);border-radius:18px;background:#fff;box-shadow:0 8px 24px rgba(16,42,67,.08);cursor:pointer;padding:16px;text-align:left;font:inherit;color:var(--ink);position:relative}.flip-card .front,.flip-card .back{display:block}.flip-card .back{display:none;color:var(--blue-dark);font-weight:750}.flip-card.flipped{background:var(--blue-soft);border-color:#b7c9df}.flip-card.flipped .front{display:none}.flip-card.flipped .back{display:block}.quiz-controls{display:flex;gap:12px;flex-wrap:wrap;align-items:center;margin:1rem 0}.quiz-controls input{width:72px;padding:7px;border:1px solid var(--line);border-radius:9px}.quiz-controls button,.tool-form button{border:0;border-radius:10px;background:var(--blue);color:#fff;font-weight:800;padding:9px 14px;cursor:pointer}.quiz-card{border:1px solid var(--line);border-radius:14px;background:#fff;padding:15px;margin:12px 0}.quiz-card.correct{border-color:#9fd1b5;background:#f3fff7}.quiz-card.incorrect{border-color:#e0a3a3;background:#fff7f7}.quiz-options{display:grid;gap:7px;margin-top:10px}.quiz-result{font-weight:850;color:var(--blue-dark);margin-top:14px}.xref{display:inline-flex;align-items:baseline;gap:.15em;color:var(--blue);font-weight:750;text-decoration:none;border-bottom:1px dotted rgba(26,79,139,.55);cursor:pointer}.xref:hover{color:var(--blue-dark);border-bottom-color:var(--blue-dark)}.xref::after{content:"↗";font-size:.72em;opacity:.62;transform:translateY(-.12em)}.xref-bubble{position:fixed;z-index:9999;width:min(600px,calc(100vw - 28px));max-height:min(72vh,540px);overflow:auto;color:var(--ink);background:#fff;border:1px solid var(--line);border-radius:16px;box-shadow:0 18px 50px rgba(15,39,66,.22);padding:0}.xref-bubble[hidden]{display:none!important}.xref-bubble-header{position:sticky;top:0;z-index:1;display:flex;align-items:center;gap:12px;padding:12px 14px;color:var(--blue-dark);background:linear-gradient(180deg,#fff,#f6faff);border-bottom:1px solid var(--line)}.xref-bubble-title{min-width:0;flex:1;font-weight:850;line-height:1.25}.xref-bubble-actions{display:flex;gap:6px}.xref-bubble-actions a,.xref-bubble-close{display:inline-flex;align-items:center;justify-content:center;min-width:30px;height:30px;border:1px solid var(--line);border-radius:9px;color:var(--blue);background:#fff;text-decoration:none;font-weight:850;cursor:pointer}.xref-bubble-body{padding:14px 16px 16px;font-size:.98rem;line-height:1.55}.xref-bubble .katex-display{overflow-x:auto;overflow-y:hidden;padding:.2rem 0}.xref-target-highlight{animation:xrefTargetFlash 1.55s ease}@keyframes xrefTargetFlash{0%{background:#fff1a6;box-shadow:0 0 0 5px rgba(255,215,80,.4)}100%{background:transparent;box-shadow:none}}:target{scroll-margin-top:calc(var(--topbar-height) + 18px)}section:target,h2:target,h3:target{animation:targetFlash 1.5s ease}@keyframes targetFlash{0%{background:#fff2bc}100%{background:transparent}}.missing-chapter,.empty-chapter{margin:22px 0;padding:18px;border-radius:14px;border:1px solid #cdd7e3;background:#fbfdff}.sidebar-backdrop{display:none}@media(max-width:980px){.book-shell{display:block}.book-sidebar{position:fixed;left:0;top:0;width:min(var(--sidebar-width),88vw);transform:translateX(-102%);transition:transform .18s ease;box-shadow:20px 0 50px rgba(0,0,0,.22)}.book-sidebar.open{transform:translateX(0)}.sidebar-backdrop.open{display:block;position:fixed;inset:0;z-index:40;background:rgba(4,14,25,.48)}.sidebar-toggle{display:inline-flex}.reader-page{width:min(100% - 22px,960px);margin-top:16px;padding:26px 22px;border-radius:14px}.topbar-title{font-size:.95rem}}@media(max-width:720px){.xref-bubble{left:10px!important;right:10px!important;top:auto!important;bottom:10px!important;width:auto;max-height:74vh;border-radius:18px}.xref-bubble-header{padding:11px 12px}.xref-bubble-body{padding:13px 13px 16px}}@media print{.book-sidebar,.book-topbar,.chapter-toolbar,.sidebar-backdrop,.quiz-section,.game-section,.web-lab-section,.xref-bubble{display:none!important}.book-shell{display:block}.reader-page{width:100%;margin:0;padding:0;border:0;box-shadow:none}.xref::after{display:none}.xref{color:inherit;border-bottom:none;font-weight:inherit}}


/* ============================================================
   Worked solutions accordions for exercises
   ============================================================ */
.solution-actions{
  display:flex;flex-wrap:wrap;align-items:center;gap:10px;margin:1.1rem 0 1.4rem;padding:12px;border:1px solid var(--line);border-radius:14px;background:#fffdf7;
}
.solution-actions button{
  border:0;border-radius:10px;background:var(--gold);color:#201400;font-weight:850;padding:9px 13px;cursor:pointer;
}
.solution-actions button:hover{filter:brightness(.96)}
.solution-count{color:var(--muted);font-weight:750;font-size:.94rem}
.solution-accordion{
  margin-top:1rem;border:1px solid #e1c070;border-radius:14px;background:#fff;overflow:hidden;
}
.solution-accordion summary{
  list-style:none;cursor:pointer;display:flex;align-items:center;gap:10px;padding:12px 14px;background:linear-gradient(180deg,#fff8dc,#fff3bd);color:#4f3400;font-weight:850;
}
.solution-accordion summary::-webkit-details-marker{display:none}
.solution-accordion summary::before{content:"▸";display:inline-block;color:#8a5a00;font-weight:900;transition:transform .15s ease}
.solution-accordion[open] summary::before{transform:rotate(90deg)}
.solution-badge{display:inline-flex;align-items:center;border-radius:999px;background:#8a5a00;color:#fff;padding:3px 8px;font-size:.78rem;text-transform:uppercase;letter-spacing:.04em}
.solution-summary-title{line-height:1.25}
.solution-body{padding:15px 16px 18px;border-top:1px solid #ead392;background:#fffef8}
.solution-body h4{margin:1rem 0 .35rem;color:#5a3b00;font-size:1.02rem}
.solution-body h4:first-child{margin-top:0}
.solution-body p{margin:.55rem 0}
.solution-body .katex-display{overflow-x:auto;overflow-y:hidden;padding:.15rem 0}
.exercise-card:has(.solution-accordion[open]){box-shadow:0 10px 28px rgba(153,102,0,.13)}
@media print{.solution-actions{display:none!important}.solution-accordion{break-inside:avoid}.solution-accordion:not([open]) .solution-body{display:block}.solution-accordion summary{border-bottom:1px solid #ddd}}

/* v3 emergency visibility fixes */
.reader-page{min-height:320px;} .chapter-content{display:block!important;visibility:visible!important;opacity:1!important;} .chapter-section{display:block!important;visibility:visible!important;} .loaded-marker{font-size:0.78rem;color:#6b7785;margin:-18px 0 18px 0;}