/* Lesson library and reading workspace. */
.lesson-directory,.lesson-page{--lesson-accent:#087a68;--lesson-border:#dce4ec;background:#f5f7fa;color:#233449;font-size:16px}
.lesson-directory [hidden],.lesson-page [hidden]{display:none!important}
.learn-hero{background:#fff;border-bottom:1px solid var(--lesson-border);padding:36px 0 40px}
.learn-hero-grid{display:grid;grid-template-columns:minmax(0,1fr) 220px;gap:64px;align-items:center}
.learn-hero h1{font:800 clamp(30px,4vw,46px)/1.16 var(--font-sans);letter-spacing:-.04em;color:var(--navy);margin:0 0 16px}
.learn-hero .eyebrow,.lesson-library .eyebrow,.lesson-nav .eyebrow{font-size:12px;letter-spacing:.12em;color:var(--lesson-accent);margin-bottom:12px}
.learn-intro{max-width:720px;font-size:17px;line-height:1.8;color:#52647a;margin:0 0 20px}
.lesson-meta{display:flex;flex-wrap:wrap;gap:8px 20px;color:#52647a;font-size:14px;margin:18px 0}
.lesson-meta span+span{position:relative}.lesson-meta span+span:before{content:'·';position:absolute;left:-12px}
.lesson-page .button{background:var(--navy);box-shadow:none;font-size:14px;border-radius:7px;padding:11px 18px}
.directory-summary{border-left:3px solid var(--lesson-accent);padding:6px 0 6px 26px;display:grid;gap:3px;color:#52647a;font-size:14px}
.directory-summary strong{font-size:48px;line-height:1.2;letter-spacing:-.05em;color:var(--navy)}
.directory-summary small{font-size:14px;margin-top:8px}
.lesson-library{padding-block:34px 70px}.library-heading{display:flex;justify-content:space-between;align-items:end;gap:24px}.library-heading h2{font-size:24px;letter-spacing:-.025em;color:var(--navy);margin:0}.library-heading .eyebrow{margin-bottom:4px}
.lesson-filter{width:min(100%,360px)}.lesson-filter label{display:block;font-weight:700;font-size:14px;margin-bottom:7px}.lesson-filter input{width:100%;padding:12px 14px;background:white;border:1px solid #bac8d6;border-radius:8px;color:var(--ink);font-size:15px;min-height:48px}
.filter-status{font-size:14px;color:#52647a;margin:20px 0 16px}.lesson-card-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}
.lesson-library-card{display:flex;flex-direction:column;background:#fff;border:1px solid var(--lesson-border);border-radius:12px;padding:24px;transition:border-color .18s,box-shadow .18s,transform .18s;min-width:0}
.lesson-library-card:hover{border-color:#7ca89f;box-shadow:0 8px 24px #10385f0d;transform:translateY(-3px)}
.lesson-card-top{display:flex;align-items:center;justify-content:space-between;margin-bottom:20px;color:#718096;font-size:13px;font-weight:700}.lesson-card-symbol{height:48px;min-width:48px;padding:0 8px;border-radius:9px;display:grid;place-items:center;background:#edf5f4;color:var(--lesson-accent);font:700 25px var(--font-display)}
.lesson-card-category{color:var(--lesson-accent);font-size:12px;font-weight:800;letter-spacing:.06em;text-transform:uppercase}.lesson-library-card h3{color:var(--navy);font-size:20px;line-height:1.4;letter-spacing:-.025em;margin:8px 0 10px}.lesson-library-card>p{font-size:15px;color:#52647a;line-height:1.75;margin:0 0 24px}.lesson-card-bottom{display:flex;align-items:center;justify-content:space-between;gap:10px;border-top:1px solid #e9eef3;padding-top:16px;margin-top:auto;font-size:13px;color:#52647a}.lesson-card-bottom b{font-size:20px;color:var(--lesson-accent)}
.lesson-empty{padding:48px 24px;text-align:center;background:#fff;border:1px dashed #bac8d6;border-radius:12px}.breadcrumbs{display:flex;flex-wrap:wrap;gap:10px;font-size:13px;color:#52647a;margin-bottom:26px}.breadcrumbs a:hover{text-decoration:underline}
.lesson-cover{background:var(--navy);border-radius:12px;color:white;padding:24px;display:grid;gap:14px}.cover-caption{font-size:11px;letter-spacing:.1em;color:#d3e6ee}.lesson-cover>strong{font:600 64px/1.3 var(--font-display);text-align:center;overflow-wrap:anywhere}.cover-footer{display:flex;gap:20px;justify-content:space-between;font-size:12px;border-top:1px solid #ffffff30;padding-top:16px;color:#d3e6ee}.cover-footer b{color:white}
.lesson-shell{display:grid;grid-template-columns:240px minmax(0,1fr);gap:40px;padding-block:36px 72px;align-items:start}.lesson-nav{position:sticky;top:24px;padding:12px 0}.lesson-nav nav{display:grid;gap:4px}.lesson-nav nav a{font-size:14px;padding:11px 12px;border-left:3px solid transparent;border-radius:0 6px 6px 0;color:#52647a}.lesson-nav nav a:hover{background:#eaf0f5;color:var(--navy)}.lesson-nav nav a[aria-current]{background:#e5efed;border-left-color:var(--lesson-accent);color:#076454;font-weight:800}.lesson-nav-note{font-size:13px;line-height:1.8;border-top:1px solid var(--lesson-border);padding:22px 12px;margin-top:24px;color:#52647a}.lesson-nav-note strong{font-weight:600}.lesson-article{min-width:0;background:#fff;border:1px solid var(--lesson-border);border-radius:12px;padding:0 40px}
.learn-section{padding:36px 0;border-bottom:1px solid var(--lesson-border);scroll-margin-top:24px}.learn-section:last-child{border:0}.section-kicker{font-size:11px;font-weight:800;color:var(--lesson-accent);letter-spacing:.12em;margin-bottom:10px}.learn-section h2{font-size:27px;line-height:1.3;letter-spacing:-.03em;color:var(--navy);margin:0 0 20px}.learn-section h3{font-size:18px;line-height:1.5;color:var(--navy);margin:0 0 7px}.learn-section p{line-height:1.85}.prerequisite,.section-lead{color:#52647a}.learning-objectives{list-style:none;padding:0;margin:20px 0 0;display:grid;gap:12px}.learning-objectives li{display:flex;gap:12px;align-items:baseline}.learning-objectives li span{color:var(--lesson-accent);font-weight:800}.concept-list{display:grid;gap:24px}.concept-item{display:flex;gap:16px}.concept-count{display:grid;place-items:center;flex:0 0 30px;height:30px;border-radius:50%;background:#eef3f7;font-size:13px;font-weight:800;color:var(--navy)}.concept-item p{margin:0;color:#52647a}
.lesson-formula{background:#edf4f9;border-left:3px solid var(--navy);padding:20px 24px;border-radius:0 8px 8px 0;overflow-wrap:anywhere}.lesson-formula>span,.insight-label{font-size:12px;font-weight:800;letter-spacing:.06em;color:var(--navy)}.lesson-formula p{font-size:22px;font-weight:800;margin:8px 0;color:var(--navy)}.lesson-formula small{font-size:14px;color:#52647a}.method-steps{padding-left:25px;display:grid;gap:14px;margin:24px 0}.method-steps li{padding-left:7px}.method-steps li::marker{font-weight:800;color:var(--lesson-accent)}.lesson-insight{background:#eff7f4;border-radius:8px;padding:20px 24px}.lesson-insight p,.lesson-caution p{margin:6px 0 0}.lesson-caution{background:#fff8e9;border-left:3px solid #c18b23;padding:20px 24px;margin-top:24px;border-radius:0 8px 8px 0}
.worked-examples{display:grid;gap:24px}.worked-example{border:1px solid var(--lesson-border);border-radius:9px;overflow:hidden}.example-heading{background:#f6f8fb;padding:18px 22px;border-bottom:1px solid var(--lesson-border)}.example-heading>span{font-size:11px;font-weight:800;color:#52647a;letter-spacing:.08em}.example-heading h3{margin:4px 0 0}.example-question{padding:0 22px;font-weight:700}.worked-example ol{padding:0 24px 0 44px;display:grid;gap:10px;color:#52647a}.example-answer{padding:15px 22px;background:#eef7f3;display:flex;gap:16px;flex-wrap:wrap;color:#075e4e}.example-answer>span{font-size:14px}.example-answer strong{overflow-wrap:anywhere}
.check-progress{font-size:14px;font-weight:700;color:var(--lesson-accent)}.lesson-checks{display:grid;gap:20px}.lesson-check{border:1px solid var(--lesson-border);border-radius:9px;padding:24px}.lesson-check fieldset{padding:0;margin:0 0 16px;border:0;min-width:0}.lesson-check legend{font-weight:700;padding:0;margin-bottom:16px;width:100%}.lesson-check legend>span{display:block;font-size:11px;letter-spacing:.08em;color:#52647a;margin-bottom:8px}.check-option{display:flex;align-items:baseline;gap:12px;border:1px solid var(--lesson-border);border-radius:7px;padding:12px 14px;margin-top:8px;cursor:pointer}.check-option:has(input:checked){background:#edf4f9;border-color:var(--navy)}.check-option input{accent-color:var(--navy);flex-shrink:0}.check-feedback:empty{display:none}.check-feedback{font-size:14px;font-weight:700}.is-correct{border-color:#087a68}.is-correct .check-feedback{color:#087a68}.is-incorrect{border-color:#b47727}.is-incorrect .check-feedback{color:#925514}.check-solution{font-size:14px;margin-top:16px;border-top:1px solid var(--lesson-border);padding-top:14px}.check-solution summary{cursor:pointer;color:var(--navy);font-weight:700;padding:4px 0}.check-solution p{color:#52647a}
.lesson-resources{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.lesson-resources>a{padding:20px;border:1px solid var(--lesson-border);border-radius:8px}.lesson-resources>a:hover{border-color:var(--lesson-accent)}.lesson-resources>a>span,.next-lesson div>span{font-size:11px;letter-spacing:.06em;color:#52647a;font-weight:800}.lesson-resources h3{margin-top:8px;font-size:16px}.lesson-resources p{font-size:14px;color:#52647a}.lesson-resources b{font-size:14px;color:var(--lesson-accent)}.next-lesson{display:flex;justify-content:space-between;align-items:center;gap:20px;background:#edf4f9;border-radius:8px;padding:22px;margin-top:24px}.next-lesson strong{display:block;color:var(--navy);font-size:20px}.next-lesson>span{font-size:26px}.all-lessons-link{display:inline-block;font-size:14px;color:var(--navy);font-weight:700;margin-top:24px}
.lesson-figure{margin:0;border:1px solid var(--lesson-border);border-radius:9px;overflow:hidden;background:#fafcfd}.lesson-figure figcaption{padding:16px 22px;font-size:14px;color:#52647a;border-top:1px solid var(--lesson-border);background:#fff}.visual-table-wrap{overflow:auto}.visual-table{width:100%;border-collapse:collapse;font-size:14px}.visual-table th,.visual-table td{text-align:left;padding:14px 18px;border-bottom:1px solid var(--lesson-border)}.visual-table thead{background:#edf4f9;color:var(--navy)}.visual-flow{display:flex;flex-wrap:wrap;gap:12px;padding:24px 24px 24px 44px;margin:0}.visual-flow li{flex:1 1 130px;padding:12px;background:#edf4f9;border-radius:6px;margin-left:10px}.visual-bars,.fraction-model,.ratio-model,.multiples-model{display:grid;gap:20px;padding:24px}.visual-bars>div>span{display:block;font-size:14px;margin-bottom:8px}.visual-bar-track{background:#e4ecf1;border-radius:4px;overflow:hidden}.visual-bar-fill{height:24px;background:var(--lesson-accent)}.fraction-model strong,.ratio-model strong,.multiples-model strong{font-size:14px;display:block;margin-bottom:10px}.fraction-strip{display:flex;gap:3px}.fraction-strip span{flex:1;height:34px;background:#e4ecf1;border:1px solid #bac8d6}.fraction-strip .is-filled,.hundred-grid .is-filled{background:var(--lesson-accent);border-color:var(--lesson-accent)}.percent-model{display:flex;align-items:center;justify-content:center;gap:40px;padding:28px}.hundred-grid{width:220px;display:grid;grid-template-columns:repeat(10,1fr);gap:3px}.hundred-grid span{aspect-ratio:1;background:#e4ecf1}.percent-model>div>strong{font-size:40px;color:var(--lesson-accent)}.percent-model p{margin:6px 0}.ratio-units,.multiples-model>div>div{display:flex;flex-wrap:wrap;gap:8px}.ratio-unit,.multiples-model>div>div>span{padding:10px 14px;border-radius:5px;background:#e4ecf1;font-weight:700}.ratio-color-0,.multiples-model .shared-multiple{background:#087a68!important;color:white}.ratio-color-1{background:#dbeaf6;color:var(--navy)}.lesson-diagram{display:block;width:100%;max-height:340px;padding:20px}.lesson-diagram text{font:18px var(--font-sans);fill:var(--navy)}
.lesson-directory :focus-visible,.lesson-page :focus-visible{outline:3px solid #176b87;outline-offset:4px}
@media(min-width:1500px){.lesson-page .container{max-width:1200px}}
@media(max-width:1000px){.lesson-card-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.lesson-shell{grid-template-columns:200px minmax(0,1fr);gap:24px}.lesson-article{padding:0 28px}.learn-hero-grid{gap:32px}.lesson-resources{grid-template-columns:1fr}}
@media(max-width:760px){.learn-hero{padding:26px 0}.learn-hero-grid{grid-template-columns:1fr}.directory-summary,.lesson-cover{display:none}.library-heading{align-items:stretch;flex-direction:column;gap:20px}.lesson-filter{width:100%}.lesson-shell{grid-template-columns:1fr;gap:20px;padding-top:20px}.lesson-nav{position:static;padding:16px;background:#fff;border:1px solid var(--lesson-border);border-radius:9px}.lesson-nav nav{grid-template-columns:repeat(2,minmax(0,1fr))}.lesson-nav nav a{padding:9px;font-size:13px}.lesson-nav-note{display:none}.lesson-nav .eyebrow{margin-bottom:8px}.lesson-article{padding:0 22px}.learn-section{padding:28px 0}.learn-section h2{font-size:24px}.learn-intro{font-size:16px}.lesson-library{padding-top:26px}.lesson-card-grid{gap:14px}.lesson-library-card{padding:20px}.lesson-check{padding:18px}.percent-model{gap:20px;padding:20px}.hundred-grid{width:180px}}
@media(max-width:520px){.lesson-card-grid{grid-template-columns:1fr}.lesson-library-card>p{margin-bottom:20px}.lesson-card-top{margin-bottom:14px}.lesson-article{padding:0 18px}.lesson-meta{gap:8px 16px;font-size:13px}.lesson-meta span+span:before{left:-10px}.lesson-nav nav{grid-template-columns:1fr}.lesson-nav nav a{font-size:14px}.lesson-formula{padding:18px}.lesson-formula p{font-size:19px}.percent-model{flex-wrap:wrap}.lesson-check{padding:16px}.lesson-directory .container,.lesson-page .container{width:calc(100% - 28px)}}
@media(prefers-reduced-motion:reduce){.lesson-library-card{transition:none}.lesson-library-card:hover{transform:none}}