@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Manrope:wght@400;500;600;700;800&display=swap');

:root{--paper:#f6f5ef;--card:#fffefa;--ink:#17313e;--muted:#61737a;--teal:#126c68;--teal-light:#e7f0e9;--line:#dce2db;--blue:#335ab7;--radius:20px;font-family:"DM Sans",-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none;color-scheme:light}
*{box-sizing:border-box}body{margin:0}a{color:inherit}button,input,textarea,select{font:inherit}button,a,input,textarea,select{-webkit-tap-highlight-color:transparent}a,button,input,textarea,select,summary{outline-offset:5px}a:focus-visible,button:focus-visible,input:focus-visible,textarea:focus-visible,select:focus-visible,summary:focus-visible,[tabindex]:focus-visible{outline:3px solid #42988f}button{cursor:pointer}button:disabled{cursor:default}h1,h2,h3,p{margin:0}h1,h2,h3{font-family:Manrope,"DM Sans",sans-serif}p,li{line-height:1.65}strong{font-weight:700}sub{font-size:.7em}ol{padding-left:21px;margin:12px 0}li{padding-left:5px;margin:10px 0}li::marker{color:var(--teal);font-weight:700}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.skip-link{position:fixed;z-index:100;left:20px;top:-100px;background:var(--ink);color:#fff;padding:14px 20px;border-radius:8px}.skip-link:focus{top:12px}.site-header{max-width:1264px;margin:auto;display:flex;align-items:center;justify-content:space-between;gap:24px;padding:25px 40px;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:11px;text-decoration:none;font-weight:800;font-size:21px;line-height:1.1;letter-spacing:-.5px}.brand-mark{width:42px;height:44px;border:2px solid var(--teal);display:grid;place-items:center;color:var(--teal);font-size:38px;border-radius:11px;line-height:1}.brand small{display:block;font-size:10px;letter-spacing:2px;font-weight:500;margin-top:6px}.site-header nav{display:flex;flex-wrap:wrap;gap:26px;align-items:center;font-size:13px;font-weight:500}.site-header nav a{text-decoration:none}.site-header nav [aria-current]{color:var(--teal);text-decoration:underline;text-underline-offset:7px}main{max-width:1184px;margin:auto;padding:54px 40px 0}.page-intro{max-width:800px}.eyebrow{font-size:10px;font-weight:700;letter-spacing:1.7px;color:var(--teal)}h1{font-size:clamp(38px,5.3vw,67px);line-height:1.13;letter-spacing:-2.8px;margin:17px 0 24px;font-weight:700}h1 em{font-family:Georgia,serif;font-weight:400;color:var(--teal);letter-spacing:-2px}.intro-copy{max-width:665px;color:var(--muted);font-size:16px}.intro-facts{display:flex;gap:12px 25px;flex-wrap:wrap;font-size:11px;color:#526a6c;margin-top:23px}.intro-facts span{display:flex;align-items:center;gap:8px}.intro-facts span::before{content:"";width:5px;height:5px;background:#79908b;border-radius:50%}.activity-nav{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:36px 0 18px}.activity-nav a{display:flex;gap:13px;align-items:center;text-decoration:none;border:1px solid var(--line);border-radius:13px;padding:20px 16px;background:rgba(255,255,255,.5);transition:background .15s,border-color .15s}.activity-nav a:hover{background:#fff}.activity-nav [aria-current]{background:var(--ink)!important;border-color:var(--ink);color:#fff}.activity-number{font-size:11px;align-self:flex-start;padding-top:3px;color:#70928e;font-variant-numeric:tabular-nums}.activity-nav [aria-current] .activity-number{color:#acd7cb}.activity-nav strong{font-size:13px;display:block;line-height:1.4}.activity-nav small{font-size:10px;color:var(--muted);display:block;margin-top:6px}.activity-nav [aria-current] small{color:#bfcdcd}.activity-nav a>span:last-child{margin-left:auto;font-size:17px}.workspace-note{display:flex;gap:11px;align-items:flex-start;font-size:10px;color:#61746e;border-bottom:1px solid var(--line);padding:8px 2px 21px;margin-bottom:30px}.workspace-note>span:first-child{font-size:18px;color:var(--teal)}.workspace-note p{max-width:710px}.workspace-note #save-status{white-space:nowrap;margin-left:auto;font-size:10px;padding-top:2px}.activity{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:32px;margin-top:20px;scroll-margin-top:20px}.activity[hidden]{display:none}.activity-heading{display:flex;justify-content:space-between;gap:25px;align-items:center}.activity h2{font-size:30px;letter-spacing:-1.1px;line-height:1.2;margin:10px 0}.activity-heading p:last-child{font-size:13px;color:var(--muted);max-width:550px}.button{display:inline-flex;justify-content:center;align-items:center;gap:14px;font-size:11px;font-weight:700;text-decoration:none;border:1px solid #cfd8cf;background:transparent;border-radius:7px;padding:13px 17px;color:var(--ink);min-height:44px;line-height:1.4;white-space:normal}.button:hover{background:#edf1e9}.button.primary{background:var(--teal);border-color:var(--teal);color:white}.button.primary:hover{background:#0d5855}.open-experiment{flex-shrink:0}.lesson-meta{display:flex;flex-wrap:wrap;gap:10px 25px;font-size:10px;color:var(--muted);margin:23px 0 21px;border-top:1px solid var(--line);padding-top:19px}.lesson-meta strong{color:var(--ink);font-weight:700;margin-right:5px}.goal{border:1px solid #d4e3d7;background:#edf3eb;border-radius:10px;padding:16px 19px}.goal>span{font-size:9px;letter-spacing:1px;text-transform:uppercase;font-weight:700;color:var(--teal)}.goal p{font-size:13px;margin-top:5px;max-width:780px}.lesson-grid{display:grid;grid-template-columns:minmax(0,1fr) 215px;gap:31px;margin-top:30px}.lesson-main{min-width:0}.lesson-step{margin-bottom:27px}.step-heading{display:flex;align-items:center;gap:11px;margin-bottom:12px}.step-heading>span{font-size:11px;display:grid;place-items:center;flex:0 0 25px;height:25px;border:1px solid #bdd4c7;border-radius:50%;color:var(--teal);font-weight:700}.step-heading h3{font-size:15px;line-height:1.4;letter-spacing:-.2px}.step-heading small{font-size:9px;color:var(--muted);font-family:"DM Sans",sans-serif;font-weight:400;margin-left:6px;white-space:nowrap}.lesson-step p,.lesson-step li{font-size:12px;color:#435e66}.lesson-step p.small-note,.small-note{font-size:10px;color:var(--muted);margin-top:12px;line-height:1.6}textarea,input[type=text],input[type=url],select{border:1px solid #d5dfd4;background:#fdfdf9;border-radius:6px;color:var(--ink);max-width:100%}textarea{display:block;width:100%;resize:vertical;padding:13px;font-size:12px;line-height:1.6;min-height:94px;margin-top:12px}textarea::placeholder{color:#86928a;font-size:11px}input[type=text]{width:100%;min-width:48px;padding:9px 7px;font-size:12px;min-height:39px}input[type=url]{width:100%;font-size:11px;padding:12px}.lesson-aside{border-left:1px solid var(--line);padding-left:23px}.lesson-aside section{margin-bottom:27px}.lesson-aside h3{font-size:13px;line-height:1.55;letter-spacing:-.2px;margin-bottom:9px}.lesson-aside .eyebrow{font-size:8px;margin-bottom:9px}.lesson-aside p{font-size:11px;color:#627277;line-height:1.8}.lesson-aside .formula{font-size:18px;color:var(--teal);font-family:Georgia,serif;line-height:1.7;margin-top:14px}.formula small{font-size:10px;font-family:"DM Sans",sans-serif}.table-scroll{overflow-x:auto;margin-top:10px;border:1px solid var(--line);border-radius:8px}table{width:100%;border-collapse:collapse;min-width:360px;table-layout:fixed;text-align:left}caption{font-size:10px;color:var(--muted);text-align:left;padding:11px 12px;background:#f5f6ee;line-height:1.5;border-bottom:1px solid var(--line)}th,td{padding:8px;border-bottom:1px solid var(--line);font-size:10px;vertical-align:middle}thead th{font-size:9px;font-weight:700;background:#f3f6ee;color:#476260;line-height:1.5}tbody th{font-size:10px;font-weight:500;line-height:1.5}tbody tr:last-child th,tbody tr:last-child td{border-bottom:0}#circuit table th:first-child{width:36%}#energy table th:first-child{width:32%}#cylinder table th:first-child,#cylinder table th:nth-child(2){width:21%}.teacher-notes{border:1px solid #cddfda;background:#f2f6ef;border-radius:9px;font-size:12px;margin-top:5px}.teacher-notes summary{cursor:pointer;padding:16px 19px;color:var(--teal);font-weight:700}.teacher-notes>div{padding:0 19px 17px}.teacher-notes p{font-size:11px;color:#4f6869;margin-top:11px}.worksheet-tools{display:grid;grid-template-columns:1fr 1fr;gap:35px;padding:32px 0 37px;border-bottom:1px solid var(--line)}.worksheet-tools h2,.share-section h2,.feedback-section h2{font-size:23px;letter-spacing:-.7px;margin:9px 0 13px}.worksheet-tools p:not(.eyebrow),.share-section>div>p:not(.eyebrow),.feedback-section>div>p:not(.eyebrow){font-size:12px;color:var(--muted);max-width:440px}.tool-actions{display:flex;align-content:center;gap:9px;flex-wrap:wrap;justify-content:flex-end}.tool-actions .button{flex:1 1 45%;font-size:10px}.tool-actions .quiet{background:transparent;flex:1 1 100%;font-weight:500}.text-button{font-size:10px;border:0;background:none;text-decoration:underline;text-underline-offset:4px;padding:5px;min-height:35px}.danger{color:#856b5e}.share-section,.feedback-section{display:grid;grid-template-columns:1fr 1fr;gap:45px;padding:40px 0;border-bottom:1px solid var(--line)}.share-buttons{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:15px}.share-buttons .button{font-size:10px;padding:10px 12px}.share-controls>label,form label,.tagged-link label{display:block;font-size:10px;color:#4e6868;margin-bottom:7px;font-weight:500}.share-status{font-size:10px;min-height:16px;margin-top:9px;color:var(--teal)}.tagged-link{font-size:10px;border-top:1px solid var(--line);padding-top:13px}.tagged-link summary{cursor:pointer;color:#55766c}.tagged-link>div{padding-top:12px}.tagged-link p{font-size:10px;margin-top:10px;color:var(--muted)}select{width:100%;font-size:11px;padding:10px;min-height:41px}.feedback-row{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-bottom:15px}.feedback-row select{display:block;margin-top:8px}.feedback-section textarea{margin-top:0}.feedback-section form>.button{margin-top:12px;font-size:10px}.feedback-section .small-note{font-size:9px;line-height:1.6}footer{max-width:1264px;margin:0 auto;display:flex;align-items:center;justify-content:space-between;padding:31px 40px;gap:20px;font-size:10px;color:var(--muted)}.footer-brand{font-size:15px;font-weight:700;color:var(--ink);text-decoration:none}.footer-brand span{font-size:10px;font-weight:400;margin-left:7px}footer>a:last-child{font-size:10px;text-decoration:none}footer p{font-size:10px}.no-script{background:#fff4d7;padding:20px;text-align:center;font-size:13px}.print-answer{display:none}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{transition:none!important;scroll-behavior:auto!important}}
[hidden]{display:none!important}.site-header nav .current-language{color:var(--teal);font-weight:700}.site-header nav [data-language]{font-size:11px}
.about-section{display:grid;grid-template-columns:1fr 1fr;gap:45px;padding:37px 0;border-bottom:1px solid var(--line);scroll-margin-top:24px}.about-section h2{font-size:23px;letter-spacing:-.7px;margin:9px 0 13px}.about-section p:not(.eyebrow){font-size:12px;color:var(--muted);margin-bottom:12px}.about-section a{font-size:11px;color:var(--teal);text-underline-offset:4px}@media(max-width:760px){.about-section{grid-template-columns:1fr;gap:12px;padding:30px 0}}@media print{.about-section{display:none!important}}
@media(max-width:1000px){.site-header{padding:22px 28px}main{padding:42px 28px 0}.lesson-grid{grid-template-columns:minmax(0,1fr) 180px;gap:22px}.activity{padding:26px}.lesson-aside{padding-left:18px}.activity-heading{gap:18px}.open-experiment{font-size:10px;padding:12px}.activity h2{font-size:26px}.activity-nav a{padding:17px 12px;gap:10px}.activity-nav strong{font-size:11px}.activity-nav small{font-size:9px}.activity-number{font-size:9px}}
@media(max-width:760px){.site-header{align-items:flex-start;gap:15px;padding:20px}.brand{font-size:18px}.brand-mark{width:35px;height:38px;font-size:32px}.brand small{font-size:9px}.site-header nav{gap:10px 14px;justify-content:flex-end;font-size:11px;max-width:260px;padding-top:4px}main{padding:35px 20px 0}h1{font-size:46px;letter-spacing:-2px}.intro-copy{font-size:14px}.activity-nav{grid-template-columns:1fr;margin-top:28px;gap:7px}.activity-nav a{padding:14px;gap:14px}.activity-nav strong{font-size:12px}.activity-nav small{font-size:10px;margin-top:3px}.activity-number{font-size:11px;align-self:center;padding:0}.workspace-note{flex-wrap:wrap;gap:7px}.workspace-note p{flex:1}.workspace-note #save-status{flex:1 0 100%;margin-left:24px;font-size:9px}.activity{padding:23px 18px;border-radius:14px}.activity-heading{display:block}.open-experiment{margin-top:18px;min-height:44px;font-size:11px}.activity h2{font-size:27px}.activity-heading p:last-child{font-size:12px}.lesson-meta{gap:8px 18px;font-size:9px}.lesson-grid{grid-template-columns:1fr;gap:8px;margin-top:24px}.lesson-aside{border-left:0;border-top:1px solid var(--line);padding:20px 0 0;display:grid;grid-template-columns:1fr 1fr;gap:18px}.lesson-aside section{margin:0}.lesson-aside section:nth-child(2){grid-row:span 2}.lesson-aside p{font-size:10px}.lesson-aside h3{font-size:12px}.lesson-aside .formula{font-size:17px}.teacher-notes{margin-top:24px}.worksheet-tools,.share-section,.feedback-section{grid-template-columns:1fr;gap:23px;padding:30px 0}.tool-actions{justify-content:flex-start}.tool-actions .button{font-size:11px}.worksheet-tools h2,.share-section h2,.feedback-section h2{font-size:24px}.worksheet-tools p:not(.eyebrow),.share-section>div>p:not(.eyebrow),.feedback-section>div>p:not(.eyebrow){max-width:560px}footer{padding:25px 20px;flex-wrap:wrap;gap:15px}footer p{display:none}th,td{padding:7px}#energy table{min-width:430px}.table-scroll{margin-right:-1px}.goal{padding:14px}.goal p{font-size:12px}}
@media(max-width:390px){.site-header nav{max-width:170px;font-size:10px;gap:10px}.brand{font-size:16px}.brand small{letter-spacing:1px}.brand-mark{width:31px;height:35px}.intro-facts{font-size:10px;gap:10px 15px}h1{font-size:39px}.activity{padding:21px 14px}.step-heading{gap:8px}.step-heading h3{font-size:13px}.step-heading small{font-size:8px}.lesson-aside{grid-template-columns:1fr}.lesson-aside section:nth-child(2){grid-row:auto}.share-buttons .button{font-size:9px;padding:10px}.feedback-row{grid-template-columns:1fr}}
@media print{
  @page{size:auto;margin:14mm 12mm}html,body{background:#fff;color:#111;font-family:Arial,sans-serif;font-size:10pt}*{box-shadow:none!important;text-shadow:none!important}.site-header,.page-intro,.activity-nav,.workspace-note,.worksheet-tools,.share-section,.feedback-section,footer,.open-experiment,.skip-link,.no-script{display:none!important}main{max-width:none;padding:0;margin:0}.activity,.activity[hidden]{display:none!important}.activity.print-active{display:block!important;border:0;padding:0;margin:0}.activity-heading{display:block}.activity h2{font-size:21pt;line-height:1.15;letter-spacing:-.5pt;margin:6pt 0}.activity-heading p:last-child{font-size:9pt;color:#333}.eyebrow{font-size:7pt;color:#333;letter-spacing:1pt}.lesson-meta{font-size:7pt;padding-top:8pt;margin:10pt 0;gap:6pt 14pt;border-color:#bbb}.goal{background:#fff!important;border:1px solid #aaa;border-radius:0;padding:8pt}.goal>span{font-size:7pt;color:#222}.goal p{font-size:9pt;margin-top:4pt}.lesson-grid{display:block;margin-top:13pt}.lesson-step{margin:0 0 13pt;break-inside:avoid-page}.step-heading{margin-bottom:6pt;gap:7pt}.step-heading>span{border-color:#888;color:#111;flex-basis:18pt;width:18pt;height:18pt;font-size:8pt}.step-heading h3{font-size:10pt}.step-heading small{font-size:7pt}.lesson-step p,.lesson-step li{font-size:8.5pt;line-height:1.5;color:#222}.lesson-step ol{margin:5pt 0;padding-left:16pt}.lesson-step li{margin:5pt 0}.lesson-step .small-note{font-size:7pt;color:#444}.lesson-aside{display:none!important}textarea,input[type=text]{display:none!important}.print-answer{display:block;min-height:14pt;border-bottom:1px solid #bbb;white-space:pre-wrap;overflow-wrap:anywhere;font-family:Arial,sans-serif;font-size:8.5pt;padding:5pt 0;line-height:1.5}.lesson-step> .print-answer{min-height:40pt}.table-scroll{overflow:visible;border:1px solid #aaa;border-radius:0;margin-top:7pt}table,#energy table{min-width:0!important;table-layout:fixed;width:100%}caption{font-size:7.5pt;background:#fff!important;padding:6pt;border-color:#aaa}th,td{padding:5pt;font-size:8pt;border-color:#bbb;vertical-align:middle}thead th{font-size:7.5pt;color:#222;background:#eee!important}tbody th{font-size:7.5pt}td .print-answer{font-size:8pt;min-height:17pt;padding:2pt 0;border:0}body[data-print-mode=student] .teacher-notes,.teacher-notes:not([open]){display:none!important}.teacher-notes{border:1px solid #aaa;background:#fff!important;border-radius:0;margin:12pt 0 0;break-inside:avoid-page}.teacher-notes summary{font-size:10pt;color:#111;padding:8pt;list-style:none}.teacher-notes>div{display:block!important;padding:0 8pt 8pt}.teacher-notes p{font-size:8pt;color:#222;margin-top:7pt;line-height:1.5}body[data-print-mode=teacher] .lesson-aside{display:grid!important;grid-template-columns:1fr 1fr;border-left:0;border-top:1px solid #aaa;padding:10pt 0 0;gap:12pt;margin-top:10pt;break-inside:avoid-page}body[data-print-mode=teacher] .lesson-aside section{margin:0}body[data-print-mode=teacher] .lesson-aside h3{font-size:9pt}body[data-print-mode=teacher] .lesson-aside p{font-size:8pt;color:#222;line-height:1.5}body[data-print-mode=teacher] .lesson-aside .formula{font-size:12pt;color:#111}a{color:#111;text-decoration:none}h2,h3{break-after:avoid-page}
  body:not(.has-js) .activity{display:block!important;break-before:page;border:0;padding:0}body:not(.has-js) .activity:first-of-type{break-before:auto}
}
@media(max-width:760px){.workspace-note #save-status{flex:1 1 calc(100% - 24px);min-width:0;max-width:calc(100% - 24px);white-space:normal;overflow-wrap:anywhere}}