#topics-app{min-width:0}.topics-intro h2{font:600 36px/1.2 var(--display);letter-spacing:-.035em;color:var(--blue-night);margin:10px 0 16px}.topic-kicker{font-size:11px;letter-spacing:.08em;font-weight:600;text-transform:uppercase;color:#58739b;margin:0 0 12px}.topic-muted{color:var(--muted);font-size:14px;line-height:1.8}.topics-toolbar{padding:22px;background:#f5f7fc;border:1px solid var(--line);border-radius:10px;display:grid;gap:18px;margin:28px 0 18px}.topic-grade-list,.topic-area-filters{display:flex;flex-wrap:wrap;gap:8px}.topic-button{border:1px solid #d0daea;border-radius:6px;background:#fff;color:var(--blue-deep);font:500 13px/1.4 var(--display);padding:10px 14px;min-height:44px;cursor:pointer}.topic-button:hover{background:#edf3fc}.topic-button[aria-pressed=true],.topic-button.primary{background:#294f91;color:#fff;border-color:#294f91}.topic-button:disabled{opacity:.45;cursor:default}.topic-button:focus-visible,.topic-link:focus-visible,.topic-card:focus-visible{outline:2px solid var(--blue);outline-offset:3px}.topic-grade-list .topic-button{min-width:44px}.topic-search input{display:block;width:100%;min-height:48px;border:1px solid #c8d6e8;border-radius:6px;padding:12px 15px;font:400 15px var(--display);background:#fff;color:var(--blue-night)}.topic-count{font-size:13px;color:var(--muted);margin:18px 0}.topic-preview{display:grid;grid-template-columns:minmax(0,.75fr) minmax(0,1.25fr);gap:28px;padding:30px;background:#eef3fb;border:1px solid #dce6f3;border-radius:12px;margin-bottom:44px}.topic-preview-copy{align-self:center}.topic-preview h3{font:600 29px/1.25 var(--display);letter-spacing:-.025em;color:var(--blue-night);margin:0 0 16px}.topic-link{display:inline-flex;align-items:center;min-height:44px;color:var(--blue-deep);font-size:14px;font-weight:600;line-height:1.7}.topic-preview-copy>.topic-link{margin-top:10px}.topic-group{margin:40px 0;scroll-margin-top:110px}.topic-group-heading{display:flex;align-items:center;gap:16px;margin:0 0 20px}.topic-group-heading img{width:32px;height:32px;flex:none}.topic-group-heading h2{font:600 27px/1.3 var(--display);color:var(--blue-night);margin:0}.topic-group-heading p{margin:4px 0 0}.topic-group-count{margin-left:auto;font-size:13px;color:#7b8ca4;border:1px solid var(--line);padding:6px 12px;border-radius:20px}.topic-card-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px}.topic-card{display:flex;flex-direction:column;align-items:flex-start;border:1px solid var(--line);border-radius:9px;padding:24px;min-width:0;background:#fff;transition:border-color .15s,background .15s}.topic-card:hover{border-color:#8ca8d3;background:#fafcff}.topic-card-meta{font-size:11px;color:#6682a9}.topic-card h3{font:600 21px/1.4 var(--display);color:var(--blue-night);margin:14px 0 12px;overflow-wrap:anywhere}.topic-card p{font-size:13px;line-height:1.8;color:var(--muted);margin:0 0 18px}.topic-card-open{margin-top:auto;font-size:13px;font-weight:600;color:#315d9f}.topic-card-grid:has(.topic-card:only-child){grid-template-columns:minmax(0,1fr)}.topic-card:only-child{display:grid;grid-template-columns:minmax(170px,.7fr) minmax(0,1.3fr) auto;align-items:center;gap:12px 26px}.topic-card:only-child .topic-card-meta{grid-column:1/-1}.topic-card:only-child h3,.topic-card:only-child p{margin:0}.topic-sources{font-size:13px;color:#7b8ba0;border-top:1px solid var(--line);padding-top:24px;margin-top:40px;line-height:1.8}.topic-sources a{color:#526f99}.topic-empty{padding:40px 22px;text-align:center;border:1px dashed #cad7e8;border-radius:8px;color:var(--muted)}.topics-detail .page-hero{display:none}.topics-detail .page-section{padding-top:30px}.topic-lesson-heading{max-width:900px;margin:30px 0}.topic-lesson-heading h1{font:600 clamp(30px,4.3vw,52px)/1.2 var(--display);letter-spacing:-.035em;color:var(--blue-night);margin:0}.topic-lesson-layout{display:grid;grid-template-columns:minmax(0,1fr) minmax(250px,.42fr);gap:32px;align-items:start}.topic-lesson-main,.topic-lesson-aside{min-width:0}.topic-text-block h2{font:600 26px/1.3 var(--display);color:var(--blue-night);margin:0 0 18px}.topic-text-block>p{color:#50647e;font-size:16px;line-height:1.95;margin:0 0 24px}.topic-formula{font-family:var(--display);font-weight:500;color:#2b5598!important;background:#f0f4fb;border-left:3px solid #537fbd;padding:18px 20px;overflow-wrap:anywhere}.topic-lesson-demo{padding:24px;border:1px solid #d5e1f0;border-radius:12px;background:#f5f8fd;margin:30px 0 38px}.topic-question{padding:20px;border:1px solid var(--line);border-radius:7px;background:#fff}.topic-solution{border:1px solid var(--line);border-radius:8px;padding:20px}.topic-solution summary{cursor:pointer;color:#315d9f;font-size:15px;font-weight:600;min-height:28px}.topic-solution p{font-size:15px;line-height:1.95;color:#49617f;margin:18px 0 0}.topic-practice{background:#fff;border:1px solid #d6e1ef;border-radius:10px;padding:24px}.topic-practice h2{font:500 20px/1.6 var(--display);color:var(--blue-night);margin:0 0 22px}.topic-practice label{display:grid;gap:8px;color:#617797;font-size:13px}.topic-practice input{width:100%;min-width:0;border:1px solid #bfcfe4;border-radius:6px;padding:12px;font:400 16px var(--display);min-height:48px}.topic-practice .topic-muted{font-size:12px;margin:10px 0 20px}.topic-practice button{margin:0 6px 8px 0}.topic-feedback{font-size:14px;line-height:1.8;color:#9a6242;margin:12px 0 0}.topic-feedback.correct{color:#24785c}.topic-next{margin-top:24px;padding:22px;background:#f3f6fb;border-radius:8px}.topic-next .topic-link{font-size:16px}.topic-visual{min-width:0}.demo-controls{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px 20px}.demo-control{display:grid;grid-template-columns:1fr auto;gap:6px;font-size:12px;color:#516c92;min-width:0}.demo-control output{font-size:14px;font-weight:600;color:#284f91}.demo-control input[type=range]{grid-column:1/-1;width:100%;min-width:0;min-height:28px;accent-color:#3567c8;cursor:pointer}.demo-control select{grid-column:1/-1;min-width:0;max-width:100%;padding:9px;border:1px solid #c5d4e8;border-radius:5px;background:#fff;font:400 13px var(--display);color:#294f91;min-height:42px}.demo-check{font-size:13px;color:#526b8b;display:flex;align-items:center;gap:8px;grid-column:1/-1}.demo-stage{margin-top:18px;min-width:0;padding:14px;background:#fff;border-radius:8px;text-align:center;overflow-wrap:anywhere}.demo-stage svg{display:block;width:100%;height:auto;max-height:310px;overflow:visible;font-family:var(--display)}.demo-result{display:block;font:600 20px/1.7 var(--display);color:#2a518f;overflow-wrap:anywhere;margin:6px 0}.demo-note,.demo-statement{font-size:13px;color:#66809e;line-height:1.8;margin:8px 0}.demo-stage>.topic-button{margin:10px 5px 0}.demo-position-strip,.demo-edge-buttons{display:flex;justify-content:center;gap:6px;flex-wrap:wrap;margin:16px 0 0}.demo-position-strip span{display:grid;place-items:center;width:28px;height:28px;border-radius:4px;font-size:12px}.demo-position-strip .winning{color:#356a58;background:#e0f0e9}.demo-position-strip .losing{color:#9d6435;background:#fcf0d9}.demo-edge-buttons .topic-button{padding:6px 9px;min-height:36px;font-size:12px}@media(max-width:1000px){.topic-card-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.topic-preview{grid-template-columns:minmax(0,1fr)}.topic-lesson-layout{grid-template-columns:minmax(0,1fr) minmax(230px,.5fr);gap:22px}.topic-card:only-child{grid-template-columns:minmax(0,1fr) auto}.topic-card:only-child h3{grid-column:1/-1}.topic-card:only-child .topic-card-open{align-self:end}}@media(max-width:760px){.topic-lesson-layout{grid-template-columns:minmax(0,1fr)}.topic-lesson-aside{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:18px}.topic-next{margin-top:0}.topic-practice{padding:20px}}@media(max-width:600px){.topics-intro h2{font-size:29px}.topics-toolbar{padding:16px;gap:14px}.topic-grade-list{gap:6px}.topic-grade-list .topic-button{min-width:40px;padding:9px 10px}.topic-area-filters .topic-button{font-size:12px;padding:9px 11px}.topic-search input{font-size:16px}.topic-preview{padding:18px;gap:20px;margin-bottom:32px}.topic-preview h3{font-size:25px}.topic-card-grid{grid-template-columns:minmax(0,1fr)}.topic-card,.topic-card:only-child{display:flex;padding:20px;gap:0}.topic-card h3,.topic-card:only-child h3{margin:12px 0}.topic-card p,.topic-card:only-child p{margin:0 0 18px}.topic-group-heading{gap:12px}.topic-group-heading h2{font-size:23px}.topic-group-heading img{width:26px;height:26px}.topic-group-heading p{font-size:12px}.topic-lesson-aside{grid-template-columns:minmax(0,1fr)}.topic-lesson-heading{margin:24px 0}.topic-lesson-demo{padding:15px}.topic-text-block>p{font-size:15px;line-height:1.9}.topic-formula{padding:14px}.demo-controls{gap:14px 16px}.demo-control select{font-size:16px}.demo-stage{padding:10px}.demo-result{font-size:17px}.demo-stage svg{min-height:140px}.topic-solution{padding:16px}.topic-solution p{font-size:14px}.topic-lesson-heading h1{font-size:32px}}@media(prefers-reduced-motion:reduce){.topic-card{transition:none}}

/* Topic catalog: one introduction, clear filters and a compact learning map. */
body[data-page='topics'] .page-hero { display: none; }
body[data-page='topics']:not(.topics-detail) .page-section { padding-top: 38px; }
.topics-intro { display: flex; justify-content: space-between; align-items: center; gap: 40px; margin-bottom: 30px; }
.topics-intro-copy { max-width: 620px; }
.topics-intro .topic-kicker { margin-bottom: 12px; }
.topics-intro h1 { font: 600 clamp(36px,4.5vw,56px)/1.12 var(--display); letter-spacing: -.045em; color: var(--blue-night); margin: 0 0 16px; }
.topics-intro .topic-muted { max-width: 540px; margin: 0; font-size: 15px; }
.topic-stats { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 26px; margin: 0; flex: none; }
.topic-stats > div { display: flex; flex-direction: column-reverse; gap: 8px; padding-left: 22px; border-left: 1px solid #dce4ef; }
.topic-stats dt { font-size: 12px; color: #6b7e97; line-height: 1.5; }
.topic-stats dd { margin: 0; font: 500 30px/1.15 var(--display); letter-spacing: -.03em; color: #2e5595; white-space: nowrap; }
.topics-toolbar { margin: 0 0 26px; padding: 24px; gap: 20px; background: #fff; border: 1px solid #dce5f0; border-radius: 14px; box-shadow: 0 5px 22px #243e6405; }
.topic-filter-heading { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; }
.topic-filter-heading h2 { margin: 0; font: 600 18px/1.4 var(--display); color: var(--blue-night); }
.topic-filter-heading p { margin: 0; font-size: 12px; }
.topic-grade-list { display: grid; grid-template-columns: 140px repeat(12,minmax(0,1fr)); gap: 8px; }
.topic-grade-list .topic-button { min-width: 0; padding: 11px 5px; min-height: 46px; font-size: 14px; border-color: #dce5f0; border-radius: 8px; background: #f7f9fc; }
.topic-grade-list .topic-button:first-child { padding-inline: 12px; font-size: 12px; }
.topic-grade-list .topic-button[aria-pressed='true'] { background: #2b559b; border-color: #2b559b; color: white; box-shadow: 0 3px 7px #2b559b20; }
.topic-search-row { display: grid; min-width: 0; }
.topic-search { position: relative; display: block; min-width: 0; }
.topic-search::before { content: ''; position: absolute; left: 15px; top: 16px; width: 18px; height: 18px; background: #7890ad; mask: url('assets/search.svg') center/contain no-repeat; pointer-events: none; }
.topic-search input { min-height: 50px; padding-left: 44px; border-radius: 8px; border-color: #dde5ef; background: #f8fafc; font-size: 14px; }
.topic-search input:focus { background: #fff; }
.topic-mobile-area { display: none; min-width: 0; }
.topic-area-filters { gap: 8px; }
.topic-area-filters .topic-button { display: inline-flex; align-items: center; gap: 8px; border-radius: 8px; font-size: 12px; padding-inline: 12px; min-height: 44px; }
.topic-area-filters img { width: 16px; height: 16px; flex: none; }
.topic-area-filters .topic-button[aria-pressed='true'] { background: #edf3ff; color: #2b559b; border-color: #b9cdee; }
.topic-preview { position: relative; grid-template-columns: minmax(0,.85fr) minmax(0,1.15fr); align-items: center; padding: 28px; gap: 36px; margin-bottom: 36px; border-radius: 16px; border-color: #d8e5f6; background: linear-gradient(120deg,#eef4ff,#f5f8fd); }
.topic-preview[hidden] { display: none; }
.topic-preview-meta { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; margin-bottom: 18px; font-size: 11px; color: #647e9e; }
.topic-preview-badge { padding: 6px 9px; border: 1px solid #c7dfda; border-radius: 5px; background: #edf7f3; color: #387764; font-size: 9px; font-weight: 600; letter-spacing: .06em; }
.topic-preview h2 { font: 600 29px/1.25 var(--display); letter-spacing: -.035em; color: var(--blue-night); margin: 0 0 14px; }
.topic-preview-copy > .topic-muted { display: -webkit-box; -webkit-box-orient: vertical; -webkit-line-clamp: 3; overflow: hidden; margin: 0; font-size: 13px; }
.topic-preview-copy > .topic-link { margin-top: 20px; padding: 10px 15px; min-height: 44px; border-radius: 7px; background: #2b559b; color: #fff; font-size: 12px; }
.topic-preview-copy > .topic-link:hover { background: #203f78; }
.topic-preview .demo-stage { margin-top: 12px; padding: 12px; border: 1px solid #e4ebf6; border-radius: 10px; }
.topic-preview .demo-stage svg { max-height: 205px; min-height: 0; }
.topic-preview .demo-result { font-size: 18px; margin: 0; }
.topic-results-heading { display: flex; justify-content: space-between; align-items: baseline; gap: 20px; margin: 0 0 20px; }
.topic-results-heading > h2 { margin: 0; font: 600 25px/1.3 var(--display); letter-spacing: -.025em; color: var(--blue-night); }
.topic-count { margin: 0; font-size: 12px; }
.topic-grade-groups { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 18px; }
.topic-grade-groups:has(> .topic-group:only-child) { grid-template-columns: minmax(0,1fr); }
.topic-grade-groups > .topic-group { --topic-tint: #eef3ff; margin: 0; border: 1px solid #dfe6ef; border-radius: 13px; background: #fff; overflow: hidden; transition: border-color .15s,box-shadow .15s; }
.topic-grade-groups > .topic-group:hover { border-color: #b7cbe8; box-shadow: 0 5px 20px #203b6108; }
.topic-grade-groups > [data-area='geometry'] { --topic-tint: #eaf6f3; }
.topic-grade-groups > [data-area='combinatorics'] { --topic-tint: #fff6e9; }
.topic-grade-groups > [data-area='logic'] { --topic-tint: #f2effb; }
.topic-grade-groups .topic-group-heading { margin: 0; padding: 18px 20px; gap: 11px; border-bottom: 1px solid #edf1f7; }
.topic-grade-groups .topic-group-heading img { width: 38px; height: 38px; padding: 8px; border-radius: 10px; background: var(--topic-tint); }
.topic-grade-groups .topic-group-heading h2 { font-size: 15px; line-height: 1.4; }
.topic-grade-groups .topic-group-heading p,.topic-grade-groups .topic-group-count { display: none; }
.topic-grade-groups .topic-card-grid { display: block; }
.topic-grade-groups .topic-card { display: flex; flex-direction: column; align-items: flex-start; gap: 0; padding: 20px; min-height: 244px; border: none; border-radius: 0; }
.topic-grade-groups .topic-card:hover { background: #fbfcff; }
.topic-grade-groups .topic-card:focus-visible { outline-offset: -4px; }
.topic-grade-groups .topic-card-meta { font-size: 10px; }
.topic-grade-groups .topic-card h3 { margin: 12px 0; font-size: 21px; line-height: 1.4; }
.topic-grade-groups .topic-card p { max-width: 70ch; margin: 0 0 20px; display: -webkit-box; -webkit-box-orient: vertical; -webkit-line-clamp: 3; overflow: hidden; }
.topic-grade-groups .topic-card-open { margin-top: auto; padding-top: 6px; }
.topic-grade-groups > .topic-empty { grid-column: 1/-1; }
.topic-sources { margin-top: 32px; font-size: 12px; }
.topic-sources p { margin: 6px 0; }
@media(max-width:1100px) {
 .topics-intro { gap: 28px; }.topic-stats { gap: 16px; }.topic-stats > div { padding-left: 16px; }.topic-stats dd { font-size: 26px; }
 .topic-grade-list { grid-template-columns: repeat(12,minmax(0,1fr)); }.topic-grade-list .topic-button:first-child { grid-column: 1/-1; justify-self: start; }
 .topic-grade-groups { grid-template-columns: repeat(2,minmax(0,1fr)); }
 .topic-preview { gap: 24px; padding: 24px; }.topic-preview h2 { font-size: 26px; }
}
@media(max-width:820px) {
 .topics-intro { align-items: flex-start; }.topic-stats { gap: 10px; grid-template-columns: 1fr; }.topic-stats > div { flex-direction: row-reverse; justify-content: flex-end; align-items: baseline; gap: 10px; padding-left: 16px; }.topic-stats dd { font-size: 21px; }.topic-stats dt { font-size: 11px; }
 .topic-filter-heading p { max-width: 260px; text-align: right; }
 .topic-preview { grid-template-columns: minmax(0,1fr) minmax(0,1fr); gap: 22px; }.topic-preview-meta { gap: 8px; }.topic-preview .demo-controls { grid-template-columns: minmax(0,1fr); gap: 8px; }.topic-preview .demo-stage svg { max-height: 180px; }
}
@media(max-width:700px) {
 .topic-grade-list { grid-template-columns: repeat(6,minmax(0,1fr)); }.topic-grade-list .topic-button:first-child { justify-self: stretch; }
 .topic-area-filters { display: none; }.topic-mobile-area { display: block; }.topic-search-row { grid-template-columns: minmax(0,1fr) minmax(0,1fr); gap: 12px; }
 .topic-mobile-area select { width: 100%; min-height: 50px; border: 1px solid #dde5ef; border-radius: 8px; padding: 10px; background: #f8fafc; font: 400 14px var(--display); color: var(--blue-night); }
 .topic-search input { font-size: 16px; }
 .topic-preview { grid-template-columns: minmax(0,1fr); gap: 20px; }.topic-preview .demo-controls { grid-template-columns: repeat(2,minmax(0,1fr)); gap: 12px; }
 .topic-preview-copy > .topic-muted { display: none; }.topic-preview h2 { margin-bottom: 0; }.topic-preview-copy > .topic-link { margin-top: 14px; }.topic-preview-meta { margin-bottom: 12px; }
}
@media(max-width:600px) {
 body[data-page='topics']:not(.topics-detail) .page-section { padding-top: 24px; }
 .topics-intro { display: block; margin-bottom: 22px; }.topics-intro h1 { font-size: 38px; margin-bottom: 12px; }.topics-intro .topic-muted { font-size: 14px; line-height: 1.75; }.topics-intro .topic-kicker { font-size: 10px; }
 .topic-stats { grid-template-columns: repeat(3,minmax(0,1fr)); gap: 12px; margin-top: 24px; }.topic-stats > div { flex-direction: column-reverse; align-items: flex-start; gap: 6px; padding-left: 14px; }.topic-stats dd { font-size: 25px; }.topic-stats dt { font-size: 11px; }
 .topics-toolbar { padding: 18px; gap: 16px; margin-bottom: 20px; border-radius: 12px; }.topic-filter-heading { display: block; }.topic-filter-heading h2 { font-size: 17px; }.topic-filter-heading p { max-width: none; margin-top: 4px; text-align: left; }
 .topic-grade-list { gap: 7px; }.topic-grade-list .topic-button { min-height: 44px; padding: 9px 4px; font-size: 14px; }
 .topic-search-row { grid-template-columns: minmax(0,1fr); gap: 10px; }.topic-mobile-area select { font-size: 16px; }
 .topic-preview { padding: 18px; gap: 18px; margin-bottom: 28px; border-radius: 12px; }.topic-preview h2 { font-size: 25px; }.topic-preview-meta { font-size: 10px; gap: 8px; }.topic-preview-badge { font-size: 8px; }.topic-preview .demo-stage { padding: 10px; }.topic-preview .demo-result { font-size: 17px; }
 .topic-results-heading { display: block; margin-bottom: 16px; }.topic-results-heading > h2 { font-size: 24px; }.topic-count { margin-top: 8px; }
 .topic-grade-groups { grid-template-columns: minmax(0,1fr); gap: 14px; }.topic-grade-groups .topic-group-heading { padding: 15px 18px; }.topic-grade-groups .topic-card { padding: 18px; min-height: 0; }.topic-grade-groups .topic-card h3 { margin: 10px 0; }.topic-grade-groups .topic-card p { -webkit-line-clamp: 2; margin-bottom: 14px; font-size: 13px; }
}
@media(max-width:720px) { .topic-grade-list { grid-template-columns: repeat(6,minmax(0,1fr)); } }
@media(max-width:380px) { .topic-grade-list { grid-template-columns: repeat(4,minmax(0,1fr)); } }
@media(prefers-reduced-motion:reduce) { .topic-grade-groups > .topic-group { transition: none; } }

/* A shared path from first counting to advanced mathematics and experiments. */
body[data-page='laboratory'] .page-hero { display: none; }
body[data-page='laboratory']:not(.topics-detail) .page-section { padding-top: 38px; }
#laboratory-app { min-width: 0; }
.learning-stages { display: grid; grid-template-columns: repeat(5,minmax(0,1fr)); gap: 10px; margin: 24px 0 12px; min-width: 0; }
.learning-stage { display: grid; gap: 7px; text-align: left; padding: 16px; min-width: 0; border: 1px solid #dce5ef; border-radius: 10px; background: #fff; color: #536d90; font-family: var(--display); cursor: pointer; }
.learning-stage strong { color: #284e86; font-size: 17px; font-weight: 600; }
.learning-stage span,.learning-stage small { font-size: 11px; line-height: 1.5; }
.learning-stage small { color: #8a9bb0; }
.learning-stage[aria-pressed='true'] { background: #eef4ff; border-color: #93b2df; box-shadow: inset 0 3px #426fb6; }
.learning-stage:hover { border-color: #93b2df; }
.topic-stage-help { color: #72859e; font-size: 12px; line-height: 1.7; margin: 0 0 24px; }
.topic-grade-list { grid-template-columns: 130px 100px repeat(12,minmax(0,1fr)); }
.topic-grade-list .topic-button:nth-child(2) { font-size: 12px; }
.topic-sources > a { display: inline-block; margin: 8px 20px 0 0; }
.learning-connection { padding: 20px; margin-bottom: 20px; border-radius: 10px; background: #eaf4f1; border: 1px solid #cfe4dc; }
.learning-connection .topic-kicker { color: #528573; }
.learning-connection .topic-link { color: #23735b; font-size: 16px; }
.learning-reset { margin-top: 14px; font-size: 12px; }
.learning-experiment-title { margin: 0 0 14px; font: 600 23px/1.45 var(--display); color: #285c50; }
body[data-page='laboratory'] .topic-lesson-demo { margin-top: 0; background: #f2f8f6; border-color: #d3e5dc; }
body[data-page='laboratory'] .topic-lesson-demo .demo-stage svg { max-height: 400px; }
body[data-page='laboratory'] .topic-preview { background: linear-gradient(120deg,#eef7f3,#f6f9fc); border-color: #d6e6de; }
body[data-page='laboratory'] .topic-preview-copy > .topic-link { background: #2c7361; }
body[data-page='laboratory'] .learning-stage[aria-pressed='true'] { background: #edf7f3; border-color: #92bcac; box-shadow: inset 0 3px #39836e; }
body[data-page='laboratory'] .learning-stage strong { color: #2d6c59; }
@media(max-width:1100px) {
 .topic-grade-list { grid-template-columns: repeat(12,minmax(0,1fr)); }
 .topic-grade-list .topic-button:first-child,.topic-grade-list .topic-button:nth-child(2) { grid-column: span 6; justify-self: stretch; }
}
@media(max-width:720px) {
 .topic-grade-list { grid-template-columns: repeat(6,minmax(0,1fr)); }
 .topic-grade-list .topic-button:first-child,.topic-grade-list .topic-button:nth-child(2) { grid-column: span 3; }
 .learning-stages { display: flex; overflow-x: auto; padding: 3px 2px 10px; gap: 8px; scrollbar-width: thin; scrollbar-color: #b7c9df transparent; scroll-snap-type: x proximity; }
 .learning-stage { flex: 0 0 134px; scroll-snap-align: start; padding: 13px; }
 .learning-stage strong { font-size: 16px; }
 .learning-experiment-title { font-size: 20px; }
}
@media(max-width:600px) {
 body[data-page='laboratory']:not(.topics-detail) .page-section { padding-top: 24px; }
 .topic-stage-help { font-size: 11px; margin-bottom: 18px; }
 .learning-connection { padding: 18px; }
 body[data-page='laboratory'] .topic-lesson-demo .demo-stage svg { max-height: 300px; }
}
@media(max-width:380px) {
 .topic-grade-list { grid-template-columns: repeat(4,minmax(0,1fr)); }
 .topic-grade-list .topic-button:first-child,.topic-grade-list .topic-button:nth-child(2) { grid-column: span 2; }
}

/* Lessons: read the idea, inspect an illustration, then solve a problem. */
.topic-illustration { margin: 30px 0 36px; padding: 24px; border: 1px solid #dce5ef; border-radius: 10px; background: #f8fafd; }
.topic-illustration h2 { margin: 0 0 18px; font: 600 25px/1.4 var(--display); color: var(--blue-night); }
.topic-figure { margin: 0; padding: 16px; border: 1px solid #e5ebf4; border-radius: 8px; background: #fff; text-align: center; overflow-wrap: anywhere; }
.topic-figure svg { display: block; width: 100%; height: auto; max-height: 240px; font-family: var(--display); }
.topic-figure-result { margin: 10px 0 0; font: 600 20px/1.6 var(--display); color: #315b94; }
.topic-figure figcaption { margin: 8px 0 0; font-size: 12px; line-height: 1.8; color: #7990ac; }
.topic-illustration > .topic-muted { margin-bottom: 0; font-size: 13px; }
.topic-results-heading { margin-top: 28px; }
@media(max-width:600px) { .topic-illustration { padding: 16px; }.topic-illustration h2 { font-size: 23px; }.topic-figure { padding: 10px; }.topic-figure-result { font-size: 17px; } }
.topic-illustration > .topic-link { margin-top: 12px; padding: 9px 14px; border: 1px solid #c3d3e9; border-radius: 6px; background: #fff; font-size: 13px; }