.skip-link{z-index:100;background:var(--ink);color:#fff;font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-medium);border-radius:0 0 10px 10px;padding:10px 16px;position:absolute;top:-100px;left:16px}.skip-link:focus{top:0}.sr-only{clip:rect(0, 0, 0, 0);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}.topbar{z-index:40;background:var(--bg-translucent);-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);border-bottom:1px solid var(--border);align-items:center;gap:14px;padding:0 24px;display:flex;position:sticky;top:0}.hamburger{border:1px solid var(--border);background:var(--card);border-radius:10px;flex-shrink:0;justify-content:center;align-items:center;width:44px;height:44px;display:none}.hamburger span,.hamburger span:before,.hamburger span:after{content:"";background:var(--ink-soft);width:16px;height:2px;display:block;position:relative}.hamburger span:before{position:absolute;top:-5px}.hamburger span:after{position:absolute;top:5px}.topbar-search-btn{border:1px solid var(--border);background:var(--card);width:44px;height:44px;color:var(--ink-soft);cursor:pointer;border-radius:10px;flex-shrink:0;justify-content:center;align-items:center;font-size:19px;line-height:1;display:none}.brand{align-items:center;gap:10px;display:flex}.brand-logo{width:auto;height:44px;display:block}.brand small{font-weight:var(--weight-regular);color:var(--muted);font-size:var(--text-caption)}.topbar-spacer{flex:1}.role-toggle{border:1px solid var(--accent);background:var(--accent-soft);font-size:var(--text-ui);border-radius:999px;align-items:center;gap:8px;padding:4px;display:flex}.role-toggle button{color:var(--accent-ink);font-weight:var(--weight-medium);font-size:var(--text-ui);background:0 0;border:none;border-radius:999px;padding:6px 12px}.role-toggle button.active{background:var(--accent);color:var(--on-accent)}.user-chip{white-space:nowrap;font-size:var(--text-caption);color:var(--ink-soft);background:var(--card);border:1px solid var(--border);border-radius:999px;align-items:center;gap:6px;padding:5px 10px;display:flex}.user-chip .dot{background:var(--accent);border-radius:50%;width:5px;height:5px}.user-chip.is-guest .dot{background:var(--muted)}.user-chip b{color:var(--ink)}.topbar-link{font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft);cursor:pointer;white-space:nowrap;background:0 0;border:none;padding:8px 4px;font-family:inherit}.topbar-link:hover{color:var(--ink)}.topbar-account-placeholder{visibility:hidden;pointer-events:none}.btn{font-size:var(--text-ui);font-weight:var(--weight-bold);font-family:var(--font-ui);border:none;border-radius:10px;justify-content:center;align-items:center;gap:6px;padding:9px 18px;display:inline-flex}.btn-primary{background:var(--ink);color:#fff}.btn-primary:hover{background:#000}.btn-accent{background:var(--accent);color:var(--on-accent)}.btn-accent:hover{background:var(--accent-ink);color:#fff}.btn-ghost{background:var(--card);color:var(--ink);border:1px solid var(--border)}.btn-ghost:hover{background:var(--border-soft)}.btn-block{width:100%}.btn:disabled{opacity:.5;cursor:default}.layout{align-items:flex-start;display:flex}.sidebar{scrollbar-gutter:stable;flex:none;width:clamp(300px,28vw,350px);max-height:calc(100vh - 45px);padding:22px 14px 60px;position:sticky;top:45px;overflow-y:auto}.tree{font-size:var(--text-ui)}.tree-school{margin-bottom:2px}.tree-school-row{font-weight:var(--weight-bold);color:var(--ink);border-radius:10px;align-items:center;gap:6px;padding:7px 10px;display:flex}.tree-school-row:hover{background:var(--border-soft)}.tree-school.open>.tree-school-row .chev{transform:rotate(90deg)}.chev{color:var(--muted);font-size:14px;transition:all .15s;display:inline-block}.tree-chev-btn{background:0 0;border:none;flex:none;justify-content:center;align-items:center;padding:0;display:inline-flex}.tree-label{flex:1;min-width:0}.tree-label.active{color:var(--accent-ink)}.tree-school-row.active,.tree-year-row.active{background:var(--accent-soft)}.tree-year{margin:2px 0 2px 10px}.tree-year-row{font-weight:var(--weight-medium);font-size:var(--text-ui);color:var(--ink-soft);border-radius:8px;align-items:center;gap:6px;padding:7px 10px;display:flex}.tree-concepts .tree-year{margin-left:6px}.tree-concepts .tree-year-row{font-weight:var(--weight-regular);padding-inline:6px}.tree-year-row:hover{background:var(--border-soft)}.tree-year.open>.tree-year-row .chev{transform:rotate(90deg)}.tree-items{flex-direction:column;gap:1px;margin:2px 0 8px 12px;display:flex}.tree-item{font-size:var(--text-ui);color:var(--ink-soft);cursor:pointer;border-radius:8px;justify-content:space-between;align-items:center;gap:8px;padding:7px 10px;display:flex}.tree-problem-group{align-items:baseline;gap:8px;padding-left:10px;display:flex}.tree-problem-group-title{width:9em;max-width:45%;font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft);word-break:keep-all;flex:none;padding:6px 0;line-height:1.4}.tree-problem-links{flex-wrap:wrap;flex:1;gap:2px 1px;min-width:0;display:flex}.tree-problem-links>.tree-item{white-space:nowrap;justify-content:center;padding:6px 4px;line-height:1.4}.sidebar .tree-school-row{border-radius:6px;gap:8px;min-height:34px;padding:2px 6px}.sidebar .tree-school{margin-bottom:0}.sidebar .tree-chev-btn{flex:0 0 14px;width:14px}.sidebar .tree-school-row.active,.sidebar .tree-school[data-school] .tree-year-row{min-height:34px;padding-block:3px}.sidebar .tree-year-row.active{background:0 0}.sidebar .tree-label.active{color:var(--ink)}.sidebar .tree-year:not(.tree-topic-group-title){margin:0 0 0 16px}.sidebar .tree-year-row{min-height:36px;font-weight:var(--weight-regular);border-radius:6px;gap:8px;padding:5px 6px}.sidebar .tree-year-row.active{font-weight:var(--weight-medium)}.sidebar .tree-concepts a.tree-year-row[aria-current=page]{background:var(--border-soft);color:var(--accent-ink)}.sidebar .tree-school-row:has(>a[aria-current=page]){background:var(--border-soft);color:var(--accent-ink)}.sidebar .tree-year-row:has(>a[aria-current=page]){background:var(--border-soft);color:var(--accent-ink)}.sidebar .tree-item.active{background:var(--border-soft)}.sidebar .tree-label[aria-current=page]{color:var(--accent-ink)}.sidebar .tree-items{gap:8px;margin:2px 0 8px 24px}.sidebar .tree-problem-group{flex-direction:column;align-items:stretch;gap:2px;padding-left:0}.sidebar .tree-problem-group-title{width:auto;min-width:0;max-width:none;font-size:var(--text-ui);font-weight:var(--weight-regular);color:var(--ink-soft);flex:none;padding:2px 0}.sidebar .tree-problem-links{flex:none;gap:4px}.sidebar .tree-problem-links>.tree-item{min-width:32px;max-width:100%;min-height:30px;font-size:var(--text-ui);white-space:normal;overflow-wrap:anywhere;border-radius:6px;padding:5px 4px}.sidebar .tree-concepts .tree-year{margin-left:6px}.sidebar .tree-concepts .tree-year-row{min-height:34px;padding:3px 6px}.sidebar .tree-concepts .tree-subject-head{margin-top:5px;padding-top:5px}.tree-item:hover{background:var(--border-soft)}.tree-item.active{background:var(--accent-soft);color:var(--accent-ink);font-weight:var(--weight-bold)}.tree-item .pts{font-size:var(--text-caption);color:var(--muted)}.school-exam-row{align-self:start;min-height:32px;padding-block:4px}.school-exam-variant-title{color:var(--ink-soft);font-size:var(--text-ui);font-weight:var(--weight-medium);padding:4px 10px;display:block}.school-exam-entry{grid-template-columns:minmax(150px,180px) minmax(0,1fr);gap:4px 8px;padding-block:4px;display:grid}.school-exam-entry+.school-exam-entry{border-top:1px solid var(--border-soft)}.school-exam-unavailable{color:var(--ink);font-size:var(--text-ui)}.school-exam-unavailable>.school-exam-row{padding-inline:10px}.school-exam-status-detail{color:var(--accent-ink);padding-block:4px;overflow-wrap:anywhere;flex-wrap:wrap;align-items:baseline;gap:4px 8px;padding-left:10px;display:flex}.school-exam-status{font-weight:var(--weight-medium);white-space:nowrap}@media (max-width:560px){.school-exam-entry{grid-template-columns:minmax(0,1fr);gap:0}}.card-head{flex-wrap:wrap;align-items:flex-start;gap:8px 12px;margin-bottom:10px;display:flex}.card-head .card-label{margin-bottom:0}.sidebar-search{margin-bottom:12px}.sidebar-search-box{border:1px solid var(--border);background:var(--card);border-radius:999px;align-items:center;gap:5px;min-height:36px;padding:0 12px;display:flex}.sidebar-search-box:focus-within{border-color:var(--ink-soft);box-shadow:0 0 0 2px var(--border-soft)}.sidebar-search-icon{color:var(--muted);flex:none;font-size:15px;line-height:1}.sidebar-search-box input{min-width:0;font-family:inherit;font-size:var(--text-ui);color:var(--ink);background:0 0;border:none;outline:none;flex:1;height:34px}.sidebar-search-box input::-webkit-search-cancel-button{display:none}.sidebar-search-clear{color:var(--muted);cursor:pointer;background:0 0;border:none;flex:none;padding:6px;font-size:13px;line-height:1}.sidebar-search-clear:hover{color:var(--ink-soft)}.search-results{margin-top:10px}.search-group{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);margin:0;padding:10px 4px 4px}.search-hit{font-size:var(--text-ui);color:var(--ink-soft);border-radius:8px;padding:7px 8px;line-height:1.45;display:block}.search-hit:hover{background:var(--accent-soft);color:var(--accent-ink)}.search-hit.is-body{padding:8px}.search-hit-title{font-size:var(--text-caption);color:var(--muted);margin-bottom:2px;display:block}.search-hit-snippet{font-size:var(--text-ui);line-height:1.5;display:block}.search-note{font-size:var(--text-caption);color:var(--muted);padding:8px 8px 12px}.search-filters{grid-template-columns:minmax(0,1fr) minmax(0,.85fr);gap:6px;display:grid}.search-filters select,.search-more{border:1px solid var(--border);background:var(--card);min-width:0;min-height:36px;color:var(--ink-soft);font:inherit;font-size:var(--text-caption);border-radius:8px;padding:7px 8px}.search-more{cursor:pointer;width:100%;color:var(--accent-ink);margin:4px 0 8px}.search-more:hover{background:var(--accent-soft)}.search-more:disabled{opacity:.6;cursor:wait}.tree-mode-toggle{isolation:isolate;background:var(--border-soft);border-radius:999px;gap:0;margin-bottom:10px;padding:3px;display:flex;position:relative}.tree-mode-toggle:before{content:"";z-index:-1;background:var(--card);width:calc(33.3333% - 2px);box-shadow:0 1px 3px color-mix(in srgb, var(--ink) 10%, transparent);opacity:0;border-radius:999px;transition:transform .18s,opacity .18s;position:absolute;inset:3px auto 3px 3px}.tree-mode-toggle:has(>a.active):before{opacity:1}.tree-mode-toggle:has(>a:nth-child(2).active):before{transform:translate(100%)}.tree-mode-toggle:has(>a:nth-child(3).active):before{transform:translate(200%)}.tree-mode-toggle:not(:has(>a:nth-child(3))):before{width:calc(50% - 3px)}@media (prefers-reduced-motion:reduce){.tree-mode-toggle:before{transition:none}}.tree-mode-toggle>a{white-space:nowrap;min-height:32px;color:var(--ink-soft);font-weight:var(--weight-regular);font-size:var(--text-ui);cursor:pointer;background:0 0;border:none;border-radius:999px;flex:1;justify-content:center;align-items:center;padding:4px 8px;font-family:inherit;text-decoration:none;display:inline-flex}.tree-mode-toggle>a.active{color:var(--ink);font-weight:var(--weight-bold)}.tree-empty{font-size:var(--text-caption);color:var(--muted);padding:14px 10px;line-height:1.5}.tree-year-text{flex:1;min-width:0}.tree-tag{color:var(--accent-ink);white-space:nowrap}.tree-round-toggle{width:100%;color:var(--ink-soft);text-align:left;background:0 0;border:0}.tree-rounds{padding-left:12px}.school-exam-year+.school-exam-year{margin-top:20px}.school-exam-year-title{color:var(--ink);font-size:var(--text-ui);font-weight:var(--weight-medium);margin:0 0 6px;padding:4px 10px}a.tree-problem-group-title{text-decoration:none}.school-exam-years-compact .school-exam-year{grid-template-columns:106px minmax(0,1fr);column-gap:4px;display:grid}.school-exam-years-compact .school-exam-year+.school-exam-year{border-top:1px solid var(--border-soft);margin-top:0}.school-exam-years-compact .school-exam-year-title{white-space:nowrap;align-self:start;margin:0;padding:8px 10px}.school-exam-years-compact .school-exam-year>.tree-items{min-width:0;margin:0}.school-exam-years-compact .school-exam-entry{grid-template-columns:100px minmax(0,1fr)}@media (max-width:560px){.school-exam-years-compact .school-exam-year{grid-template-columns:86px minmax(0,1fr);column-gap:0}.school-exam-years-compact .school-exam-year-title{padding-inline:0}.school-exam-years-compact .school-exam-entry{grid-template-columns:minmax(0,1fr)}.school-exam-years-compact .tree-problem-group{gap:4px}.school-exam-years-compact .tree-problem-group-title{width:5em;max-width:40%}}
.content{flex:1;min-width:0;max-width:1000px;padding:22px 24px 100px}.crumb{font-size:var(--text-caption);color:var(--muted);margin-bottom:10px}.crumb b{color:var(--ink-soft)}.crumb a{color:var(--ink-soft);margin:-5px -3px;padding:5px 3px;text-decoration:none;display:inline-block}.crumb a:hover,.crumb a:focus-visible{color:var(--accent-ink);text-underline-offset:3px;text-decoration:underline;text-decoration-thickness:1px}.titlebar{flex-wrap:wrap;justify-content:space-between;align-items:baseline;gap:8px;margin-bottom:16px;display:flex}.titlebar h1{font-size:var(--text-title);letter-spacing:-.02em}.problem-titlebar{align-items:center}.problem-actions{gap:10px;margin-left:auto;display:flex}.problem-actions .nav-btn{font-weight:var(--weight-regular);white-space:nowrap;background:0 0;border-color:#0000;border-radius:6px;justify-content:center;gap:6px;padding:8px 10px}.problem-actions .nav-btn:hover{background:var(--border-soft)}.action-icon{width:16px;height:16px;color:var(--ink-soft);flex:none;justify-content:center;align-items:center;display:inline-flex}.action-icon svg{width:16px;height:16px;display:block}.problem-toolbar{container-type:inline-size}.problem-time-short{display:none}.nav-buttons{grid-template-columns:minmax(0,1fr) max-content minmax(0,1fr);align-items:center;gap:10px;margin-bottom:16px;display:grid}.nav-buttons-group{flex-wrap:wrap;grid-area:1/1;gap:10px;min-width:0;display:flex}.nav-buttons>.info-bar-inline{grid-area:1/2;justify-self:center}.nav-buttons>.nav-btn{grid-area:1/3;justify-self:end}.nav-btn{border:1px solid var(--border);background:var(--card);min-height:44px;font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft);border-radius:10px;align-items:center;padding:8px 14px;display:inline-flex}.nav-btn:hover{background:var(--border-soft)}.nav-btn:disabled{opacity:.35;cursor:default}.nav-buttons .nav-btn{color:var(--ink);white-space:nowrap;background:0 0;border-color:#0000;border-radius:6px;justify-content:center;gap:8px}.nav-buttons .nav-btn:hover:not(:disabled){background:var(--border-soft)}.print-btn{color:var(--ink)}.share-btn{color:var(--ink);justify-content:center;min-width:104px}.card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius-lg);box-shadow:var(--shadow);margin-bottom:16px;padding:22px;position:relative}.card-label{font-size:var(--text-ui);font-weight:var(--weight-bold);color:var(--muted);text-transform:uppercase;letter-spacing:.03em;align-items:center;gap:8px;margin-bottom:10px;display:flex}.set-group-title{color:var(--accent-ink);font-size:var(--text-body);font-weight:var(--weight-bold);letter-spacing:0;text-transform:none;margin:0;line-height:1.4}.set-list-heading{min-height:21px;color:var(--muted);align-items:center;gap:8px;display:flex}.card-icon{color:inherit;flex:none;display:inline-flex}.card-icon svg{width:15px;height:15px;display:block}.problem-text{font-size:var(--text-body);color:var(--ink);word-break:keep-all;overflow-wrap:anywhere;line-height:1.85}.problem-text p{margin:0 0 11px}.problem-text p:last-child{margin-bottom:0}.problem-text .mline{max-width:100%;margin-bottom:9px;display:block;overflow:visible}.problem-text .mline:last-child{margin-bottom:0}#probText .passage-row,#probText .item-row{grid-template-columns:max-content minmax(0,1fr);align-items:baseline;column-gap:.35em;margin-bottom:9px;display:grid}#probText .item-row{margin-bottom:1lh}#probText .passage-box .item-row,#probText .passage-row:last-child,#probText .item-row:last-child{margin-bottom:0}#probText .passage-label,#probText .item-label{white-space:nowrap}#probText .passage-body,#probText .item-body{min-width:0;display:block}#probText .item-row-nested{margin-left:1.5em}.problem-text>p.para-subq-num{margin-top:26px}#probText>p.para-subq{margin-top:0}#probText>p.para-subq~p.para-subq{margin-top:2lh}#probText>div.passage-box+p.para-subq{margin-top:0}#probText>p:not(.para-subq):has(+p.para-passage-heading){margin-bottom:0}#probText>p.para-passage-heading,.problem-text>p.para-subq:first-child,#probText>p.para-subq:first-child{margin-top:0}#probText .mline-item{padding-left:1.5em}.problem-text>p:has(.concept-note-heading):not(:first-child){margin-top:1lh}.problem-text .mline-bullet{margin-top:3.25em}.problem-text .passage-box .mline-bullet{margin-top:0}.tree-subject-head{border-top:1px solid var(--border);margin-top:5px;padding-top:10px}.concept-unit-grid{grid-template-columns:repeat(auto-fit,minmax(min(100%,220px),1fr));gap:10px;margin:0;padding:0;list-style:none;display:grid}.concept-unit-grid+.concept-unit-grid{border-top:1px solid var(--border);margin-top:14px;padding-top:14px}.concept-unit-grid>li{min-width:0}.concept-unit-card{border:1px solid var(--border);height:100%;color:var(--ink);background:var(--card);border-radius:12px;flex-direction:column;gap:7px;padding:14px 16px;text-decoration:none;display:flex}.concept-unit-card:hover,.concept-unit-card:focus-visible{border-color:var(--accent);background:var(--accent-soft)}.concept-unit-card:focus-visible{outline:2px solid var(--accent);outline-offset:2px}.concept-unit-title{color:var(--accent-ink);font-size:var(--text-body);justify-content:space-between;align-items:baseline;gap:10px;line-height:1.5;display:flex}.concept-unit-title strong{font-weight:var(--weight-medium)}.concept-unit-topics{color:var(--ink-soft);font-size:var(--text-caption);word-break:keep-all;overflow-wrap:anywhere;line-height:1.65}.concept-topic-group-title{color:var(--ink);font-size:var(--text-ui);font-weight:var(--weight-bold);letter-spacing:-.015em;margin:12px 0 4px;padding:0 10px;line-height:1.45}.concept-topic-group-title:first-child{margin-top:0}.concept-topic-group-title.tree-subject-head{margin-top:12px;padding-top:12px}.tree-topic-group-title{color:var(--ink);font-size:var(--text-ui);font-weight:var(--weight-medium);letter-spacing:-.015em;margin-top:6px;padding:6px 6px 4px;line-height:1.45}.tree-topic-group-title.tree-subject-head{margin-top:6px;padding-top:10px}.tree-school-row+.tree-topic-group-title{margin-top:0;padding-top:2px}.problem-text:first-child .mline-bullet{margin-top:0}.katex{font-size:1.1em}.katex-ko{margin-right:.1667em}.katex .minner:has(>.mclose.nulldelimiter)>.mopen:not(.nulldelimiter)+.mord:has(>.mtable>.col-align-l:first-child){margin-left:.5em}.katex-base:has(.mfrac,.op-limits,.large-op,.delimsizing){margin-top:.2em;margin-bottom:.2em}.problem-text .mline-center{text-align:center}.problem-text .mline-right{text-align:right}#probText{padding-bottom:2lh;line-height:1.85}.solution-header{justify-content:space-between;align-items:flex-start;gap:8px;margin-bottom:16px;display:flex}.solution-header>.solution-tabs{min-width:0;margin-bottom:0}.solution-footer-action{position:absolute;bottom:4px;right:22px}.solution-footer-action .content-report-link{min-height:0;padding:0}.solution-tabs{flex-wrap:wrap;gap:6px;margin-bottom:16px;display:flex}.solution-tabs button{border:1px solid var(--border);background:var(--card);font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft);font-family:var(--font-ui);white-space:nowrap;border-radius:999px;padding:6px 14px}.solution-tabs button.active{background:var(--ink);color:#fff;border-color:var(--ink)}.solution-tabs button .tab-tag{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--muted);margin-left:6px}.solution-tabs button.active .tab-tag{color:#fff9}.solution-tabs button .tab-tag-rec{color:var(--accent-ink)}.solution-tabs button.active .tab-tag-rec{color:var(--accent-highlight)}.solution-heading{font-family:var(--font-ui);font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--ink);border-bottom:1px solid var(--border-soft);margin:0 0 12px;padding-bottom:8px}.solution-heading-tag{font-size:var(--text-caption);color:var(--accent-ink);margin-left:8px}.solution-print-all>section+section{margin-top:26px}.passage-box{border:1px solid var(--border);background:var(--card);border-radius:10px;margin:0 0 16px;padding:18px 20px}.passage-box>p{margin-bottom:20px}.passage-box>p:last-child,.passage-box>figure:last-child{margin-bottom:0}.editor-note{font-family:var(--font-ui);font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--accent-ink);margin:0 0 16px;line-height:1.6}.embedded-example{border:1px solid var(--border);background:var(--card);border-radius:6px;min-width:0;margin:20px 0}.embedded-example-heading{background:var(--bg);font-family:var(--font-ui);font-size:var(--text-body);border-radius:6px 6px 0 0;flex-wrap:wrap;align-items:baseline;gap:4px 12px;padding:6px 14px;display:flex}.embedded-example-source{color:var(--muted);font-size:var(--text-ui)}.embedded-example-row{border-top:1px solid var(--border-soft);font-size:var(--text-ui);padding:12px 14px 12px 54px;position:relative}.embedded-example-label{font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-regular);color:var(--ink-soft);position:absolute;top:12px;left:14px}.embedded-example-body{min-width:0}.embedded-example-body>p{margin-bottom:10px}.embedded-example-body>:last-child{margin-bottom:0}.embedded-example-choices{break-inside:avoid;flex-wrap:wrap;justify-content:space-between;align-items:baseline;gap:12px;margin:16px 0 0;padding:0;list-style:none;display:flex}.embedded-example-choices>li{white-space:nowrap}@media (max-width:600px){.embedded-example-heading{padding:6px 12px}.embedded-example-row{padding:10px 12px 10px 48px}.embedded-example-label{top:10px;left:12px}}.problem-figure{text-align:center;margin:14px 0}.problem-figure img{width:auto;max-width:100%;height:auto;max-height:340px}.problem-figure img[src^="/figures/sets-and-propositions/"],.problem-figure img[src^="/figures/algebra-notes/"],.problem-figure img[src^="/figures/coordinate-geometry/"],.problem-figure img[src^="/figures/space-geometry-notes/"],.problem-figure img[src^="/figures/concept-notes/"],.problem-figure img[src^="/figures/exponential-logarithmic-notes/"],.problem-figure img[src^="/figures/numbers-and-operations/"]{width:100%;max-width:780px;max-height:none}:is(.problem-figure:has(>img[src^="/figures/algebra-notes/"]),.problem-figure:has(>img[src^="/figures/concept-notes/"]),.problem-figure:has(>img[src^="/figures/exponential-logarithmic-notes/"])){margin-block:0}.problem-figure img[src^="/figures/algebra-notes/"],.problem-figure img[src^="/figures/concept-notes/"],.problem-figure img[src^="/figures/exponential-logarithmic-notes/"]{margin-inline:auto;display:block}:is(.problem-figure:has(>img[src="/figures/sets-and-propositions/complements.png"]),.problem-figure:has(>img[src="/figures/numbers-and-operations/number-systems.png"])){margin-bottom:0}:is(.problem-figure:has(>img[src="/figures/sets-and-propositions/complements.png"])+.problem-figure,.problem-figure:has(>img[src="/figures/numbers-and-operations/number-systems.png"])+.problem-figure){margin-top:0}.problem-figure img[src="/figures/sets-and-propositions/complements.png"],.problem-figure img[src="/figures/numbers-and-operations/number-systems.png"]{margin-inline:auto;display:block}.problem-figure-caption{font-family:var(--font-ui);font-size:var(--text-caption);color:var(--muted);margin-top:8px}.solution-placeholder{text-align:center;color:var(--muted);font-size:var(--text-ui);font-family:var(--font-ui);padding:30px 10px}.video-solo{border-radius:var(--radius-lg);box-shadow:var(--shadow);margin-bottom:16px;overflow:hidden}.lecture-badge{font-size:var(--text-caption);font-weight:var(--weight-bold);letter-spacing:0;text-transform:none;background:var(--accent-soft);color:var(--accent-ink);border:1px solid var(--accent);border-radius:999px;padding:2px 8px;display:inline-block}.video-frame{aspect-ratio:16/6;background:radial-gradient(circle at 30% 20%, var(--accent-soft) 0%, transparent 45%), linear-gradient(135deg, var(--media-light), var(--media-shade));flex-direction:column;justify-content:center;align-items:center;gap:10px;display:flex}.video-frame.pending{aspect-ratio:auto;background:var(--bg);border:1px solid var(--border);border-radius:var(--radius-lg);flex-flow:wrap;justify-content:flex-start;align-items:baseline;gap:4px 12px;padding:14px 18px}.lecture-jump{width:fit-content;font-family:var(--font-ui);font-size:var(--text-caption);color:var(--accent-ink);margin:0 0 16px;display:block}.lecture-jump:hover{text-underline-offset:3px;text-decoration:underline}#lecture{scroll-margin-top:65px}@media print{.lecture-jump{display:none}}.video-solo:has(.video-frame.pending){box-shadow:none}.video-frame.pending .vsub{color:var(--ink-soft)}.video-frame .vlabel{font-size:var(--text-ui);color:var(--ink-soft);font-weight:var(--weight-medium)}.video-frame .vsub{font-size:var(--text-caption);color:var(--muted)}.card.concept-card{border-radius:12px;padding:0;overflow:hidden}.concept-summary{cursor:pointer;justify-content:space-between;align-items:center;gap:12px;min-height:48px;padding:12px 22px;list-style:none;display:flex}.concept-summary::-webkit-details-marker{display:none}.concept-summary-text{flex:1;min-width:0}.concept-topic{font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--ink);text-transform:none;letter-spacing:0;word-break:keep-all;overflow-wrap:anywhere;margin:0;line-height:1.5}.concept-topic-link:hover{text-underline-offset:3px;text-decoration:underline}.concept-card .chev{flex:none;font-size:14px;transition:all .15s}.concept-card[open] .concept-summary .chev{transform:rotate(90deg)}.concept-card[open] .concept-summary{border-bottom:1px solid var(--border-soft)}.concept-body{padding:0}
.concept-card:not([open]) .concept-body{display:none}.lockable{position:relative}.lock-overlay{border-radius:var(--radius-lg);-webkit-backdrop-filter:blur(3px)saturate(1.1);backdrop-filter:blur(3px)saturate(1.1);text-align:center;background:#ffffffdb;flex-direction:column;justify-content:center;align-items:center;gap:12px;padding:20px;display:flex;position:absolute;inset:0}.lock-icon{background:var(--border-soft);width:40px;height:40px;color:var(--ink-soft);border-radius:50%;justify-content:center;align-items:center;font-size:17px;display:flex}.lock-copy{font-size:var(--text-ui);color:var(--ink-soft);font-weight:var(--weight-medium)}.join-btn{background:var(--ink);color:#fff;font-size:var(--text-ui);font-weight:var(--weight-bold);border:none;border-radius:10px;padding:9px 18px;display:inline-block}.lock-standalone{text-align:center;flex-direction:column;justify-content:center;align-items:center;gap:12px;padding:40px 20px;display:flex}.lecture-gate-pending{visibility:hidden}.solution-table-wrap{-webkit-overflow-scrolling:touch;justify-content:center;max-width:100%;margin:16px 0;display:flex;overflow-x:auto}.solution-table{border-collapse:collapse;width:auto;max-width:100%;font-size:var(--text-ui)}.solution-table.is-grading{width:100%}.solution-table th,.solution-table td{border:1px solid var(--border);text-align:center;padding:9px 20px}.solution-table th{background:var(--border-soft);color:var(--ink-soft);font-weight:var(--weight-bold);font-size:var(--text-ui)}.crit-block{border-left:2px solid var(--crit-c,var(--accent));margin:0 0 18px;padding:2px 0 2px 16px;position:relative}.crit-block:last-child{margin-bottom:0}.crit-block .crit-badge{max-width:100%;font-family:var(--font-ui);font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--crit-c,var(--accent-ink));letter-spacing:.01em;margin:0 0 9px;line-height:1.4;display:block;overflow:auto hidden}.crit-block .solution-break{margin-top:18px}.crit-block .problem-text{padding:0}.crit-block .solution-table-wrap{margin:12px 0 16px}.crit-block:last-child .solution-table-wrap{margin-bottom:12px}#solText>:is(.solution-table-wrap,.problem-figure):last-child,#solText>.crit-block:last-child>:is(.solution-table-wrap,.problem-figure):last-child{margin-bottom:0}.grading-notes{font-family:var(--font-ui);font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--crit-c,var(--accent-ink));letter-spacing:.01em;margin-top:18px;line-height:1.6}.grading-notes>p{margin:0 0 9px}.grading-notes>p:last-child{margin-bottom:0}.note-box{background:var(--bg);border:0;border-radius:6px;margin:0 0 18px;padding:14px 18px}.note-box:last-child{margin-bottom:0}.note-box.note-correction{background:#f8f8f8}.note-box.note-inline{display:block}.note-box p{margin:0 0 9px}.note-box p:last-child{margin-bottom:0}.note-box .mline{margin-bottom:6px;display:block}.note-box .mline:empty,.problem-text .mline:empty{height:.9em;margin-bottom:0}.note-box .mline:last-child{margin-bottom:0}.note-box .mline:has(.note-figure){-webkit-overflow-scrolling:touch;overflow:auto hidden}.note-box .note-figure{height:auto;margin:10px auto;display:block}.note-box .note-label{font-family:var(--font-note);font-weight:var(--weight-bold);font-synthesis:none;color:var(--ink);margin:0 4px 0 0;font-size:17px;font-style:italic;line-height:1.5;display:inline}.card.info-card{padding:13px 22px}.info-bar{flex-wrap:wrap;align-items:center;display:flex}.info-bar-inline{background:var(--card);border:1px solid var(--border);box-shadow:var(--shadow);border-radius:999px;padding:9px 20px}.info-item{border-left:1px solid var(--border-soft);align-items:baseline;gap:6px;padding:0 18px;display:flex}.info-item:first-child{border-left:none;padding-left:0}.info-item:last-child{padding-right:0}.info-item .info-key{font-size:var(--text-caption);color:var(--muted);font-weight:var(--weight-bold);white-space:nowrap}.info-item .info-val{font-size:var(--text-ui);color:var(--ink);font-weight:var(--weight-medium);white-space:nowrap}.info-item .info-val.tbd{color:var(--muted);font-weight:var(--weight-medium)}@media (max-width:520px){.info-bar{gap:10px 0}.info-item{padding:0 12px}}.grading-row{border-bottom:1px solid var(--border-soft);font-size:var(--text-body);justify-content:space-between;align-items:center;gap:10px;padding:11px 0;display:flex}.grading-row:last-child{border-bottom:none}.grading-row .pt{font-weight:var(--weight-bold);color:var(--ink);white-space:nowrap;margin-left:12px}.solution-tabs button .tab-tag-mathesis{color:var(--accent-ink)}.solution-tabs button.active .tab-tag-mathesis{color:var(--accent-highlight)}.grading-total{border-top:2px solid var(--ink);font-weight:var(--weight-bold);font-size:var(--text-body);justify-content:space-between;margin-top:4px;padding-top:12px;display:flex}.related-problem-row{border-bottom:1px solid var(--border-soft);font-size:var(--text-ui);color:var(--ink-soft);justify-content:space-between;align-items:center;gap:10px;padding:12px 0;display:flex}.related-problem-row:last-child{border-bottom:none}.related-problem-row:hover,.related-problem-row .rp-main b{color:var(--ink)}.related-problem-row .rp-main{flex:1;min-width:0}.rp-no{font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-bold);color:var(--muted);font-variant-numeric:tabular-nums;flex:none;margin-right:10px}.badge{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft);border-radius:999px;padding:4px 10px}.upload-zone{border:1.5px dashed var(--border-strong);text-align:center;background:var(--field-bg);cursor:pointer;border-radius:16px;padding:34px 20px}.upload-zone:hover{background:var(--accent-soft);border-color:var(--accent-border)}.upload-zone .cam{margin-bottom:10px;font-size:30px;display:block}.upload-zone .u-main{font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink)}.upload-zone .u-sub{font-size:var(--text-caption);color:var(--muted);margin-top:6px}input[type=file]{display:none}.grading-progress{color:var(--ink-soft);font-size:var(--text-ui);font-weight:var(--weight-medium);align-items:center;gap:12px;padding:28px 10px;display:none}.spinner{border:2.5px solid var(--border);border-top-color:var(--accent);border-radius:50%;width:20px;height:20px;animation:.8s linear infinite spin}@keyframes spin{to{transform:rotate(360deg)}}.qa-empty{text-align:center;color:var(--muted);font-size:var(--text-ui);padding:26px 10px}.qa-input-row{gap:8px;margin-top:14px;display:flex}.qa-input{border:1px solid var(--border);min-width:0;font-size:var(--text-ui);background:var(--field-bg);border-radius:10px;flex:1;padding:11px 14px;font-family:inherit}.qa-send{white-space:nowrap;background:var(--ink);color:#fff;font-weight:var(--weight-bold);font-size:var(--text-ui);border:none;border-radius:10px;flex:none;padding:0 18px}.qa-item{border-bottom:1px solid var(--border-soft);font-family:var(--font-ui);padding:16px 0}.qa-item:first-child{padding-top:2px}.qa-item:last-child{border-bottom:none;padding-bottom:2px}.qa-q-head{justify-content:space-between;align-items:center;gap:10px;margin-bottom:8px;display:flex}.qa-q-meta{font-size:var(--text-caption);color:var(--muted);align-items:center;gap:8px;display:flex}.qa-pin-badge{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft);border-radius:999px;align-items:center;gap:4px;padding:3px 9px;display:inline-flex}.qa-q-text{font-size:var(--text-body);color:var(--ink);font-weight:var(--weight-medium);line-height:1.6;font-family:var(--font-serif);margin-bottom:10px}.qa-a{background:var(--border-soft);font-size:var(--text-body);color:var(--ink-soft);line-height:1.7;font-family:var(--font-serif);border-radius:12px;padding:13px 16px}.qa-a-label{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);font-family:var(--font-ui);margin-bottom:5px}.qa-pin-toggle{font-family:inherit;font-size:var(--text-caption);color:var(--muted);cursor:pointer;-webkit-user-select:none;user-select:none;white-space:nowrap;background:0 0;border:none;align-items:center;gap:6px;padding:0;display:flex}.qa-pin-toggle input{cursor:pointer;accent-color:var(--accent-ink)}.qa-pin-toggle.pinned{color:var(--accent-ink);font-weight:var(--weight-bold)}.qa-a-pending{background:var(--border-soft);font-size:var(--text-ui);color:var(--muted);border-radius:12px;padding:13px 16px}.qa-a-snippet{color:var(--muted);margin-bottom:10px}.qa-a-lock{font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--muted);flex-wrap:wrap;align-items:center;gap:8px;display:flex}.qa-a-lock-icon{font-size:15px}.qa-a-lock-link{font-size:var(--text-ui);font-weight:var(--weight-bold);color:var(--accent-ink);text-underline-offset:3px;text-decoration:underline}.qa-answer-form{flex-direction:column;gap:8px;display:flex}.qa-answer-input{border:1px solid var(--border);font-size:var(--text-body);font-family:var(--font-serif);resize:vertical;background:var(--field-bg);border-radius:10px;min-height:70px;padding:11px 14px}.qa-admin-controls{flex-direction:column;gap:8px;margin:-6px 0 14px;display:flex}.qa-answer-send{background:var(--accent);color:var(--on-accent);font-weight:var(--weight-bold);font-size:var(--text-ui);font-family:var(--font-ui);border:none;border-radius:10px;align-self:flex-end;padding:8px 16px}
.public-shell{flex-direction:column;min-height:100vh;display:flex}.public-main{flex:1;min-width:0}.site-nav{z-index:40;background:var(--bg-translucent);-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);border-bottom:1px solid var(--border);align-items:center;gap:24px;max-width:1280px;margin:0 auto;padding:16px 24px;display:flex;position:sticky;top:0}.site-nav-links{align-items:center;gap:20px;display:flex}.site-footer{border-top:1px solid var(--border);text-align:center;color:var(--muted);font-size:var(--text-caption);max-width:1280px;margin:0 auto;padding:28px 24px}.page-wrap{max-width:1000px;margin:0 auto;padding:0 24px}.hero{text-align:center;max-width:780px;margin:0 auto;padding:76px 24px 56px}.hero-eyebrow{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft);border-radius:999px;margin-bottom:18px;padding:6px 14px;display:inline-block}.hero h1{font-size:var(--text-display);letter-spacing:-.02em;color:var(--ink);line-height:1.35;font-family:var(--font-serif);font-weight:var(--weight-bold)}.hero p.lead{font-size:var(--text-body);color:var(--ink-soft);margin-top:18px;line-height:1.7}.hero-ctas{flex-wrap:wrap;justify-content:center;gap:12px;margin-top:30px;display:flex}.hero-ctas .btn{font-size:var(--text-ui);padding:13px 26px}.section{max-width:1080px;margin:0 auto;padding:40px 24px 20px}.section h2{font-size:var(--text-title);font-family:var(--font-serif);letter-spacing:-.01em;margin-bottom:8px}.section .section-sub{color:var(--ink-soft);font-size:var(--text-ui);margin-bottom:0}.notice-text{font-size:var(--text-ui);color:var(--ink);line-height:1.7}.notice-text+.notice-text{margin-top:10px}.feature-grid{grid-template-columns:repeat(3,1fr);gap:16px;display:grid}.feature-card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius-lg);box-shadow:var(--shadow);padding:24px}.text-link{color:var(--accent-ink);text-underline-offset:3px;text-decoration:underline}.yt-embed,.video-embed{background:#000;position:relative;overflow:hidden}.yt-embed{aspect-ratio:16/9;border-radius:14px;margin-top:14px}.video-embed{aspect-ratio:16/9;border-radius:0;margin-top:0}.video-play-gate{background:radial-gradient(circle at 50% 42%, var(--media-glow) 0%, transparent 42%), var(--media-dark);color:#fff;text-align:center;flex-direction:column;justify-content:center;align-items:center;gap:12px;padding:20px;display:flex;position:absolute;inset:0}.video-play-button{min-height:44px;color:var(--media-ink);font:var(--weight-bold) var(--text-ui)/1 var(--font-ui);cursor:pointer;background:#ffffffeb;border:1px solid #ffffff38;border-radius:999px;align-items:center;gap:9px;padding:10px 18px;display:inline-flex;box-shadow:0 5px 18px #0000004d}.video-play-button:hover:not(:disabled){background:#fff;transform:translateY(-1px)}.video-play-button:disabled{cursor:wait;opacity:.72}.video-play-icon{border-top:6px solid #0000;border-bottom:6px solid #0000;border-left:10px solid;width:0;height:0}.video-play-message{color:#ffffffc7;max-width:420px;font:var(--text-caption)/1.55 var(--font-ui);margin:0}.yt-embed iframe,.video-embed iframe{border:0;width:100%;height:100%;display:block}.yt-embed-cover{cursor:pointer;background:#000;border:0;width:100%;height:100%;padding:0;display:block;position:relative}.yt-embed-cover img{object-fit:cover;width:100%;height:100%;display:block}.yt-embed-play{background:#000000b8;border-radius:12px;width:64px;height:44px;transition:background .15s;position:absolute;top:50%;left:50%;transform:translate(-50%,-50%)}.yt-embed-play:after{content:"";border:10px solid #0000;border-left:16px solid #fff;border-right-width:0;position:absolute;top:50%;left:50%;transform:translate(-40%,-50%)}.yt-embed-cover:hover .yt-embed-play,.yt-embed-cover:focus-visible .yt-embed-play{background:var(--accent)}.yt-embed-cover:hover .yt-embed-play:after,.yt-embed-cover:focus-visible .yt-embed-play:after{border-left-color:var(--on-accent)}.teacher-photo{border:1px solid var(--border);border-radius:var(--radius-lg);width:min(240px,70%);height:auto;box-shadow:var(--shadow);margin:0 auto 28px;display:block}.feature-card .f-icon{margin-bottom:12px;font-size:22px}.feature-card h3{font-size:var(--text-body);margin-bottom:8px}.feature-card p{font-size:var(--text-ui);color:var(--ink-soft);line-height:1.6}.pricing-card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius-lg);box-shadow:var(--shadow);text-align:center;padding:32px}.pricing-card .price{font-size:var(--text-display);font-weight:var(--weight-bold);margin:12px 0 4px}.pricing-card .price span{font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--muted)}.pricing-list{text-align:left;font-size:var(--text-ui);color:var(--ink-soft);flex-direction:column;gap:10px;margin:24px 0;padding:0;list-style:none;display:flex}.pricing-list li{align-items:flex-start;gap:8px;display:flex}.pricing-list li:before{content:"✓";color:var(--ink-soft);font-weight:var(--weight-bold)}.pricing-note{font-size:var(--text-caption);color:var(--muted);text-align:left;margin:-8px 0 20px;line-height:1.7}.auth-shell{max-width:400px;margin:60px auto;padding:0 24px}.auth-card .btn{width:100%;margin-top:4px}.pricing-shell{max-width:480px;margin:60px auto;padding:0 24px}.pricing-title{font-family:var(--font-serif);font-size:var(--text-title);text-align:center;line-height:1.4}.pricing-shell>*+*{margin-top:16px}.pricing-shell .btn{width:100%;margin-top:12px}.pricing-card .btn{width:100%}.mypage-logout{text-align:center;margin-top:20px}.mypage-actions{flex-wrap:wrap;gap:10px;margin-top:14px;display:flex}.tag-guide-shell{max-width:720px;margin:0 auto;padding:0 24px 60px}.legal-shell{max-width:720px;margin:0 auto;padding:60px 24px 100px}.legal-shell h1{font-family:var(--font-serif);font-size:var(--text-title);letter-spacing:-.01em;margin-bottom:8px}.legal-updated{color:var(--muted);font-size:var(--text-caption);margin-bottom:32px}.legal-shell h2{font-family:var(--font-serif);font-size:var(--text-heading);margin:32px 0 10px}.legal-list{margin:0 0 14px;padding-left:20px}.legal-list li{font-family:var(--font-serif);font-size:var(--text-body);color:var(--ink);margin-bottom:6px;line-height:1.85}.legal-list .legal-list{margin-top:6px}.mypage-choice-note{border:1px solid var(--border);background:var(--border-soft);border-radius:12px;margin-top:12px;padding:12px 14px}.mypage-choice-note p{font-size:var(--text-ui);color:var(--ink-soft);line-height:1.7}.mypage-choice-note p+p{margin-top:8px}.mypage-choice-note a{color:var(--accent-ink);text-decoration:underline}.pay-notice{border:1px solid var(--border);background:var(--border-soft);text-align:left;border-radius:12px;margin:16px 0 14px;padding:14px 16px}.pay-notice-title{font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-bold);color:var(--ink);margin-bottom:8px}.pay-notice-list{margin:0 0 12px;padding-left:18px}.pay-notice-list li{font-size:var(--text-ui);color:var(--ink-soft);margin-bottom:4px;line-height:1.7}.pay-check{font-size:var(--text-ui);color:var(--ink);cursor:pointer;align-items:flex-start;gap:8px;margin-top:8px;line-height:1.6;display:flex}.pay-check input{cursor:pointer;flex:none;margin-top:3px}.pay-check a{color:var(--accent-ink);text-decoration:underline}
.study-start-links{grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin-top:20px;display:grid}.study-start-links a{color:var(--ink);word-break:keep-all;flex-direction:column;gap:10px;text-decoration:none;transition:border-color .15s;display:flex}.study-start-links a:hover{border-color:var(--accent)}.study-start-links strong{font-size:var(--text-body);color:var(--accent-ink)}.study-start-links a>span{font-size:var(--text-ui);color:var(--ink-soft);line-height:1.65}.browse-actions{word-break:keep-all;margin:0 0 20px}.lecture-finder{padding:16px 20px}.lecture-filters{border-bottom:1px solid var(--border);flex-wrap:wrap;align-items:center;gap:8px 16px;padding-bottom:12px;display:flex}.lecture-types{gap:6px;margin:0}.lecture-types button{min-height:30px;padding:4px 12px;line-height:1.5}.lecture-select,.lecture-checkbox{min-height:30px;font-size:var(--text-ui);color:var(--ink-soft);align-items:center;gap:6px;display:flex}.lecture-select select{border:1px solid var(--border);background:var(--card);max-width:220px;min-height:30px;color:var(--ink);font:inherit;border-radius:6px;padding:3px 8px}.lecture-checkbox input{width:14px;height:14px;accent-color:var(--accent-ink);margin:0}.lecture-count{font-size:var(--text-caption);color:var(--ink-soft);margin:10px 0 4px;line-height:1.5}.lecture-results .related-problem-row{min-height:32px;font-size:var(--text-ui);white-space:normal;word-break:keep-all;overflow-wrap:anywhere;padding:6px 0;line-height:1.5}.lecture-finder>.browse-actions{margin-top:12px;margin-bottom:0}.content-report{flex-shrink:0;justify-content:flex-end;display:flex}.content-report-link{min-height:44px;color:var(--ink-soft);font-size:var(--text-caption);font-weight:var(--weight-regular);white-space:nowrap;background:0 0;border:1px solid #0000;border-radius:6px;justify-content:center;align-items:center;padding:8px 10px;line-height:1.4;text-decoration:none;display:inline-flex}.content-report-link:hover{background:var(--border-soft);color:var(--ink)}.content-report-link:focus-visible{outline:2px solid var(--ink-soft);outline-offset:3px}#lecture{scroll-margin-top:70px}.study-guide{background:var(--card);border:1px solid var(--border);border-radius:12px;padding:0 22px}.study-guide-item{padding:22px 0}.study-guide-item+.study-guide-item{border-top:1px solid var(--border)}.study-guide-item h3{color:var(--ink);font-size:var(--text-body);font-weight:var(--weight-bold);word-break:keep-all;margin:0 0 10px;line-height:1.5}.study-guide-item .problem-text{color:var(--ink-soft);margin:0}.study-guide-item .problem-text+.problem-text{margin-top:10px}.tag-guide-card{margin-bottom:16px}.tag-guide-row{flex-wrap:wrap;align-items:baseline;gap:10px;margin-bottom:10px;display:flex}.tag-guide-plain,.tag-guide-tag{font-weight:var(--weight-bold);font-size:var(--text-body)}.tag-guide-plain{color:var(--ink);word-break:keep-all}.tag-guide-sub{font-size:var(--text-caption);font-weight:var(--weight-medium);color:var(--ink-soft)}.tag-guide-card .problem-text{margin:0 0 10px}.tag-guide-closing{font-size:var(--text-body);color:var(--ink-soft);text-align:center;word-break:keep-all;margin-top:36px}.tag-guide-closing .seg{display:inline-block}.br-m{display:none}@media (max-width:860px){.br-m{display:inline}}@media (max-width:380px){.tag-guide-closing{font-size:var(--text-ui)}}@media (max-width:480px){.topbar{gap:8px;padding:0 12px}}@media (max-width:360px){.topbar{gap:5px;padding:0 8px}}.note-guide-card{margin-bottom:16px}.note-guide-card .note-box{margin:0}.note-guide-label{font-size:var(--text-caption);font-weight:var(--weight-bold);letter-spacing:.06em;text-transform:uppercase;color:var(--ink-soft);margin-bottom:10px}.note-guide-heading .note-label,.note-guide-extra .note-name{font-family:var(--font-note);font-weight:var(--weight-bold);font-synthesis:none;font-style:italic}.note-guide-heading .note-label{color:var(--ink);font-size:17px;display:block}.note-guide-heading{justify-content:space-between;align-items:center;gap:14px;margin-bottom:8px;display:flex}.note-guide-color{color:var(--ink-soft);font-size:var(--text-ui);font-weight:var(--weight-bold)}.note-guide-basic-colors{gap:12px;display:grid}.note-guide-basic-colors .problem-text{grid-template-columns:116px 1fr;align-items:baseline;gap:16px;margin:0;display:grid}.note-guide-extra{font-size:var(--text-caption);color:var(--ink-soft);margin:10px 0 0}.note-guide-extra a{text-decoration:underline}.chalk-color-name{align-items:center;gap:9px;display:inline-flex}.chalk-color-swatch{border:1px solid #1717172e;border-radius:50%;flex:0 0 15px;width:15px;height:15px;box-shadow:inset 0 0 0 1px #ffffff47}.chalk-color-black{background:linear-gradient(90deg,#171717 0 50%,#fff 50% 100%)}.chalk-color-blue{background:#1447ff}.chalk-color-sky{background:#3396ff}.chalk-color-light-green{background:#2febd2}.chalk-color-yellow{background:#f7eb00}.chalk-color-orange{background:#ffcb30}.chalk-color-red{background:#ff3636}.chalk-color-purple{background:#93f}@media (max-width:560px){.note-guide-basic-colors .problem-text{grid-template-columns:1fr;gap:5px}}a.pill-link{font-size:var(--text-caption);font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft);border-radius:999px;padding:3px 12px;text-decoration:none;display:inline-block}.hero-guide{padding-top:0;padding-bottom:16px;max-width:none;padding-inline:0}.guide-nav{flex-wrap:wrap;justify-content:center;gap:8px;margin-top:22px;display:flex}.hero-guide .guide-nav{margin-top:0}.guide-nav a{font-size:var(--text-ui);font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft);white-space:nowrap;border-radius:999px;padding:6px 12px}.logo-showcase{text-align:center;padding:44px 28px 32px}.logo-showcase img{width:100%;max-width:320px;height:auto}.logo-showcase .logo-tagline{font-family:var(--font-serif);font-style:italic;font-size:var(--text-ui);color:var(--ink-soft);margin-top:18px}.auth-card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius-lg);box-shadow:var(--shadow);padding:32px}.auth-card h1,.auth-card h2{font-size:var(--text-heading);margin-bottom:6px}.auth-card .sub{color:var(--muted);font-size:var(--text-ui);margin-bottom:22px}.field{margin-bottom:14px}.check-field{align-items:center;gap:8px;margin-bottom:14px;display:flex}.delete-warn-list{font-size:var(--text-ui);color:var(--ink-soft);flex-direction:column;gap:6px;margin:0 0 14px;padding-left:18px;display:flex}.delete-actions{gap:8px;display:flex}.btn-danger{background:var(--ink);border-color:var(--ink);color:#fff}.btn-danger:hover{background:var(--ink-strong);border-color:var(--ink-strong)}.check-field input{width:16px;height:16px;accent-color:var(--accent-ink)}.check-field label{font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft)}.signup-consents{border:0;min-width:0;margin:24px 0 18px;padding:0}.signup-consents legend{font-size:var(--text-ui);font-weight:var(--weight-bold);margin-bottom:12px}.signup-consents .check-field{align-items:flex-start;line-height:1.6}.signup-consents input[type=checkbox]{flex:0 0 16px;margin-top:3px}.signup-consents-all{border-bottom:1px solid var(--border);padding-bottom:12px}.signup-consents-all label{font-size:var(--text-ui)}.signup-consents-all span{font-weight:var(--weight-regular)}.signup-consent-notice{color:var(--ink-soft);font-size:var(--text-caption);word-break:keep-all;overflow-wrap:anywhere;margin:-6px 0 16px 24px;line-height:1.7}.signup-consent-notice p{margin:6px 0}.signup-consent-notice summary{cursor:pointer}.field label{font-size:var(--text-ui);font-weight:var(--weight-medium);color:var(--ink-soft);margin-bottom:6px;display:block}.field input,.field textarea{border:1px solid var(--border);width:100%;font-size:var(--text-ui);background:var(--field-bg);border-radius:10px;padding:11px 14px;font-family:inherit}.field input:focus,.field textarea:focus{border-color:var(--accent);background:#fff;outline:none}.form-error{background:var(--bg);border:1px solid var(--border-strong);border-left:3px solid var(--ink-soft);color:var(--ink);font-size:var(--text-ui);border-radius:10px;margin-bottom:14px;padding:10px 14px 10px 42px;position:relative}.form-error:before{content:"!" / "";text-align:center;width:16px;height:16px;font:700 14px/16px var(--font-ui);border:1px solid;border-radius:50%;position:absolute;top:12px;left:14px}.form-notice{background:var(--bg);border:1px solid var(--border);color:var(--ink);font-size:var(--text-ui);border-radius:10px;margin-bottom:14px;padding:10px 14px}.form-notice-icon{font-weight:var(--weight-bold);margin-right:6px}.auth-switch{text-align:center;font-size:var(--text-ui);color:var(--ink-soft);margin-top:18px}.auth-switch a{color:var(--accent-ink);font-weight:var(--weight-bold)}.mypage-row{border-bottom:1px solid var(--border-soft);font-size:var(--text-ui);justify-content:space-between;align-items:center;padding:13px 0;display:flex}.mypage-row:last-child{border-bottom:none}.mypage-row .k{color:var(--muted)}.mypage-row .v{font-weight:var(--weight-medium)}.status-pill{font-size:var(--text-caption);font-weight:var(--weight-bold);border-radius:999px;padding:3px 10px}.status-pill.active{background:var(--accent-soft);color:var(--accent-ink)}.status-pill.inactive{background:var(--border-soft);color:var(--muted)}.status-pill.warn{background:var(--border-soft);color:var(--ink);box-shadow:inset 0 0 0 1px var(--border-strong)}.status-pill.warn:before{content:"!" / "";text-align:center;width:12px;height:12px;font:700 10px/12px var(--font-ui);border:1px solid;border-radius:50%;margin-right:4px;display:inline-block}.suspicious-row{border-bottom:1px solid var(--border-soft);font-size:var(--text-ui);justify-content:space-between;align-items:center;gap:12px;padding:13px 0;display:flex}.suspicious-row:last-child{border-bottom:none}.suspicious-row .who{flex-direction:column;gap:2px;display:flex}.suspicious-row .who .email{font-weight:var(--weight-medium)}.suspicious-row .who .name{color:var(--muted);font-size:var(--text-caption)}.suspicious-row .stats{flex-wrap:wrap;justify-content:flex-end;gap:8px;display:flex}.learning-export-form{flex-wrap:wrap;align-items:end;gap:12px;display:flex}.learning-export-form label{gap:6px;display:grid}.learning-export-form input{max-width:100%;min-height:36px}.learning-record-card p{font-size:var(--text-ui);color:var(--ink-soft);word-break:keep-all;overflow-wrap:anywhere;margin:12px 0;line-height:1.7}.learning-record-card .sub{margin-bottom:16px;line-height:1.6}.learning-export-form input{border:1px solid var(--border);color:var(--ink);background:var(--card);border-radius:6px;padding:6px;font-family:inherit}@media (max-width:480px){.learning-record-card{padding:24px}}
.scrim{background:var(--overlay);z-index:45;display:none;position:fixed;inset:0}.scrim.show{display:block}@media (max-width:860px){.lecture-finder .lecture-types button,.lecture-finder .lecture-select,.lecture-finder .lecture-select select,.lecture-finder .lecture-checkbox{min-height:36px}.lecture-select{min-width:0;max-width:100%}.lecture-select select{min-width:0;max-width:100%;font-size:var(--text-body)}.lecture-results .related-problem-row{min-height:36px}.hamburger,.topbar-search-btn{display:flex}.sidebar-search-box input,.search-filters select{font-size:var(--text-body)}.search-filters{grid-template-columns:minmax(0,1fr) 116px}.layout{display:block}.sidebar{background:var(--card);z-index:50;width:82%;max-width:340px;height:100%;max-height:none;padding-top:16px;transition:transform .22s;position:fixed;top:0;left:0;transform:translate(-105%);box-shadow:20px 0 40px #00000026}.sidebar.open{transform:translate(0)}.sidebar-head{border-bottom:1px solid var(--border);justify-content:space-between;align-items:center;margin-bottom:10px;padding:6px 14px 14px;display:flex!important}.sidebar-head-logo{width:auto;height:36px;display:block}.sidebar-close{border:1px solid var(--border);width:44px;height:44px;color:var(--ink-soft);background:#fff;border-radius:8px;font-size:16px}.content{padding:16px 16px 90px}.titlebar h1{font-size:var(--text-heading)}.tree-chev-btn{position:relative}.tree-chev-btn:before{content:"";width:34px;height:36px;position:absolute;top:50%;right:-2px;transform:translateY(-50%)}.concept-topic-link{margin:-10px 0;padding:10px 0;display:inline-block}.card{border-radius:var(--radius-lg);padding:16px}.brand small{display:none}.brand-logo{height:36px}.role-toggle,.user-chip,.topbar-signout{display:none}.solution-table th,.solution-table td{padding:8px 10px}.concept-summary{flex-wrap:wrap;row-gap:4px}.feature-grid{grid-template-columns:1fr}.hero h1{font-size:var(--text-title)}.site-nav-links{gap:12px}}@media (max-width:420px){.problem-text{font-size:var(--text-ui)}}@media (max-width:560px){.problem-titlebar{flex-wrap:nowrap;gap:8px;margin-bottom:8px}.problem-titlebar h1{min-width:0;font-size:var(--text-heading);text-overflow:ellipsis;white-space:nowrap;overflow:hidden}.problem-actions{flex:none;gap:0}.problem-actions .nav-btn{width:44px;min-width:44px;padding:0}.problem-action-label{clip-path:inset(50%);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}}@container (max-width:520px){.nav-buttons{gap:4px}.nav-buttons .nav-btn{width:44px;min-width:44px;padding:0}.nav-buttons .info-bar-inline{flex-wrap:nowrap;padding:9px 8px}.nav-buttons .info-item{gap:4px;padding:0 8px}.nav-buttons .info-item:first-child{padding-left:0}.nav-buttons .info-item:last-child{padding-right:0}.nav-buttons .info-val.tbd{font-size:var(--text-caption)}.problem-time-short{display:inline}.problem-nav-label,.problem-time-label{clip-path:inset(50%);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}}.sidebar-head,.qa-count-print,.print-source-note{display:none}@media (max-width:640px){.study-start-links{grid-template-columns:1fr}}
@media print{.embedded-example,.embedded-example-row,.embedded-example-body{break-inside:auto;page-break-inside:auto;height:auto;max-height:none;overflow:visible}.embedded-example-heading,.embedded-example-label{break-after:avoid}.topbar,.sidebar,.hamburger,.nav-buttons,.problem-actions,.video-solo,.concept-card,.feedback-card,.content-report,.lock-overlay,.grading-card,.qa-card:not(.has-pinned),.solution-tabs,.qa-input-row,.qa-attach-preview,.qa-pin-toggle,.qa-answer-form,.qa-empty,.qa-item:not(.pinned),#qaCount{display:none!important}.qa-count-print{display:inline!important}body{background:#fff}.content{max-width:100%;margin:0;padding:0 4px}.card,.solution-card,.passage-box{break-inside:auto;page-break-inside:auto}.card{box-shadow:none;border:1px solid var(--border)}.solution-card .crit-block,.solution-card .note-box,.solution-card .solution-table-wrap,.problem-figure{break-inside:avoid;page-break-inside:avoid}.solution-card{break-before:page;page-break-before:always}.solution-heading{break-after:avoid;page-break-after:avoid}.solution-print-branded{table-layout:fixed;border-collapse:collapse;border:0;width:100%}.solution-print-branded>thead{break-inside:avoid;display:table-header-group}.solution-print-branded>tbody>tr,.solution-print-branded>tbody>tr>td{break-inside:auto}.solution-print-branded>thead>tr>td,.solution-print-branded>tbody>tr>td{vertical-align:top;border:0;padding:0}.solution-print-brand{border-bottom:1px solid var(--muted);color:var(--ink);justify-content:space-between;align-items:center;gap:12px;margin:0 0 14px;padding:0 0 10px;display:flex}.solution-print-brand .solution-heading{border:0;margin:0 0 5px;padding:0}.solution-print-brand img{flex:none;width:110px;height:47px;display:block}.solution-print-attribution{font-family:var(--font-ui);font-size:var(--text-caption);color:var(--ink);line-height:1.5}.problem-figure img{max-width:100%!important;height:auto!important}.katex-mathml{display:none!important}.crumb,.titlebar{break-inside:avoid}.print-source-note{font-family:var(--font-ui);font-size:var(--text-caption);color:var(--ink);break-after:avoid;page-break-after:avoid;margin:0 0 10px;display:block}.site-footer{break-inside:avoid;page-break-inside:avoid;padding:8px 0 6px}.biz-info{color:var(--ink)!important}}
.school-titlebar{justify-content:flex-start;gap:8px 12px}.school-video-link{white-space:nowrap;margin-left:auto}.school-admissions-link{font-family:var(--font-ui);font-size:var(--text-ui);color:var(--accent-ink);text-underline-offset:3px;white-space:nowrap;line-height:1.6}.school-admissions-link:hover,.school-admissions-link:focus-visible{text-decoration:underline}.row-note{font-family:var(--font-ui);font-size:var(--text-caption);font-weight:var(--weight-medium);color:var(--accent-ink);margin-left:8px}.exam-total{font-weight:var(--weight-bold);color:var(--accent-ink);background:var(--accent-soft)}.exam-points-note{font-size:var(--text-caption);color:var(--ink-soft);white-space:pre-line;margin:0 0 12px;line-height:1.5}.exam-table-scroll{border:1px solid var(--border);border-radius:10px;max-width:100%;overflow-x:auto}.exam-table{border-collapse:separate;border-spacing:0;width:100%;font-size:var(--text-ui);text-align:center;font-variant-numeric:tabular-nums;line-height:1.5}.exam-table th,.exam-table td{border-right:1px solid var(--border);border-bottom:1px solid var(--border);white-space:nowrap;min-width:80px;padding:10px 8px}.exam-table tr>:last-child{border-right:0}.exam-table tbody tr:last-child>*{border-bottom:0}.exam-table thead th{background:var(--accent-soft)}.exam-table tr>:first-child{z-index:1;background:var(--bg);color:var(--ink-soft);font-weight:var(--weight-medium);position:sticky;left:0}.exam-problem-link,.exam-problem-pending{justify-content:center;min-width:44px;padding:5px 10px;display:inline-flex}.exam-problem-link{border:1px solid var(--border);background:var(--card);color:var(--accent-ink);font-weight:var(--weight-bold);border-radius:6px}.exam-problem-link:hover{border-color:var(--accent);background:var(--accent-soft)}.exam-problem-link:focus-visible,.exam-table-scroll:focus-visible{outline:2px solid var(--accent);outline-offset:-2px}.exam-problem-pending{color:var(--muted);font-weight:var(--weight-regular)}.exam-problem-note{max-width:16ch;color:var(--accent-ink);font-size:var(--text-caption);font-weight:var(--weight-regular);white-space:normal;word-break:keep-all;margin:6px auto 0;display:block}.rp-part{color:var(--muted);margin-left:5px}.biz-info{font-size:var(--text-caption);color:var(--muted);margin-bottom:10px;line-height:1.8}.biz-info a{color:inherit}.spec-table-wrap{-webkit-overflow-scrolling:touch;max-width:100%;overflow-x:auto}.spec-table{border-collapse:collapse;width:100%;font-size:var(--text-ui);table-layout:fixed}.spec-col-basic,.spec-col-scope{width:50%}.spec-table th,.spec-table td{border:1px solid var(--border);text-align:left;vertical-align:top;padding:9px 12px;line-height:1.6}.spec-table thead th{background:var(--accent-soft);color:var(--accent-ink);font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-bold);text-align:center}.spec-table tbody th{background:var(--border-soft);color:var(--muted);font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-bold)}.spec-table td.spec-cell-center{text-align:center}.spec-paren{font-family:var(--font-ui);font-size:var(--text-caption);font-weight:var(--weight-regular);color:var(--muted);white-space:nowrap;margin-left:5px}.spec-paren.is-wrap{white-space:normal;word-break:keep-all}.spec-sub{font-family:var(--font-ui);font-size:var(--text-caption);color:var(--muted);display:block}.spec-part+.spec-part{border-top:1px dashed var(--border);margin-top:6px;padding-top:6px}.spec-part-label{font-family:var(--font-ui);font-size:var(--text-caption);font-weight:var(--weight-bold);letter-spacing:.03em;color:var(--accent-ink);margin-right:6px;display:inline}.spec-scope{color:var(--ink-soft)}.quota-section{border-top:1px solid var(--border);margin-top:20px;padding-top:16px}.quota-section:first-of-type{margin-top:14px}.quota-title{font-family:var(--font-ui);font-size:var(--text-body);font-weight:var(--weight-bold);color:var(--ink);text-transform:none;letter-spacing:0;flex-wrap:wrap;align-items:baseline}.quota-date{font-size:var(--text-caption);font-weight:var(--weight-regular);color:var(--muted)}.quota-track-title{font-size:var(--text-ui);color:var(--ink);text-transform:none;margin-top:0}.quota-units-body>tr:first-child>th,.quota-criteria-body>tr:first-child>th{color:var(--accent-ink);background:var(--accent-soft)}.quota-criteria-body>tr:first-child>th{text-align:center}.quota-csat-line{font-size:var(--text-ui);color:var(--ink-soft);line-height:1.7}.spec-table>tbody:not(.quota-units-body)>tr>td{font-family:var(--font-ui);font-size:var(--text-ui);font-weight:var(--weight-regular);color:var(--ink-soft);text-align:center;vertical-align:middle;line-height:1.6}.spec-table>tbody:not(.quota-units-body)>tr>td :is(b,.spec-paren,.spec-sub,.spec-part-label,.spec-scope,.quota-csat-line){font:inherit;color:inherit;letter-spacing:normal}.quota-units-head{grid-template-columns:minmax(0,1fr) auto minmax(0,1fr);align-items:baseline;gap:8px;display:grid}.quota-units-head>span{grid-column:2}.quota-units-head>b{font-variant-numeric:tabular-nums;grid-column:3;justify-self:end}.quota-tree{columns:2;column-rule:1px solid var(--border);column-gap:20px}.quota-college{break-inside:avoid;margin-bottom:12px}.quota-college:last-child{margin-bottom:0}.quota-college-name{font-family:var(--font-ui);font-size:var(--text-caption);font-weight:var(--weight-bold);letter-spacing:.03em;color:var(--accent-ink);text-align:left;margin-bottom:3px}.quota-unit-table{table-layout:fixed;border-collapse:collapse;width:100%}.quota-stat-col{width:19%}.spec-table .quota-unit-table th,.spec-table .quota-unit-table td{font-size:var(--text-caption);vertical-align:middle;padding:6px 4px;line-height:1.6}.spec-table .quota-unit-table thead th{white-space:nowrap;text-align:center;background:var(--accent-soft);color:var(--accent-ink)}.spec-table .quota-unit-table tbody th{color:var(--ink-soft);font-weight:var(--weight-regular);overflow-wrap:anywhere;background:0 0}.spec-table .quota-unit-table td{text-align:center;font-variant-numeric:tabular-nums;color:var(--accent-ink)}.quota-rate{white-space:nowrap;grid-template-columns:minmax(5ch,max-content) auto 1ch;align-items:baseline;gap:2px;display:inline-grid}.quota-rate>:first-child{text-align:right;white-space:nowrap}.quota-rate>:last-child{text-align:left;white-space:nowrap}@media (max-width:1100px){.quota-tree{columns:1}}@media (max-width:560px){.spec-table th,.spec-table td{padding:7px 8px}.quota-tree{columns:1}}.grading-exclusion-notice{color:var(--accent,#996000);margin-bottom:1rem;font-weight:700}.excluded-problem-original>summary{cursor:pointer;color:var(--accent,#996000);padding:.75rem 0}.excluded-problem-original[open]>summary{margin-bottom:1rem}