/* PhysicsHelp shared visual system. Native HTML remains the interaction baseline. */
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body{background:linear-gradient(180deg,#eaf3f1 0,#f7f8f5 420px)}
header{max-width:none;background:#163c4b;color:white;padding:18px max(24px,calc((100vw - 1200px)/2));border:0;box-shadow:0 3px 15px #163c4b18}
header .brand{color:#fff;letter-spacing:-.04em;font-size:27px;white-space:nowrap}header .brand span{color:#8cddd3}header .brand small{margin-left:2px;color:#d3e6e7}header nav{gap:12px 22px;font-size:.86rem}header nav a{color:#f2faf8;text-decoration:none;font-weight:600}header nav a:hover{text-decoration:underline}.nav-search{border:1px solid #9cbcbc;padding:0 13px;border-radius:6px}
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.home-hero{display:grid;grid-template-columns:1.35fr 1fr;gap:50px;align-items:center;padding:24px 0 40px}.home-hero h1{font-size:clamp(2rem,4.2vw,3.4rem);line-height:1.05;margin:18px 0 24px}.home-hero h1 span{color:#08777a}.hero-figure{margin:0;border:1px solid #bbd1cd;background:#e0eeea;border-radius:24px;padding:24px}.hero-figure svg{width:100%;display:block;fill:none;stroke-width:3}.hero-grid{stroke:#bfd7d2;stroke-width:1}.hero-wave{stroke:#087d80}.hero-vector{stroke:#a44f2b}.hero-circuit{stroke:#163c4b}.hero-figure text{fill:#163c4b;stroke:none;font:18px system-ui}.hero-figure figcaption{font-weight:650;color:#385d63}.site-search{max-width:650px}.site-search .inline{align-items:stretch}.site-search input{min-width:0}.board-links a{font-weight:650}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:20px}.section-heading a{font-size:.9rem}.topic-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:18px;margin:20px 0 40px}.topic-card{color:var(--ink);background:var(--paper);border:1px solid var(--line);border-radius:8px;text-decoration:none;padding:23px;display:flex;flex-direction:column;transition:border-color .15s}.topic-card:hover{border-color:var(--accent)}.topic-card h2{font-size:1.2rem}.topic-card p{font-size:.9rem;flex:1;color:#4c626b}.topic-card>span:last-child{font-size:.85rem;font-weight:650;color:#075e79}.scope-note{padding-top:24px;color:#536a73;border-top:1px solid var(--line);font-size:.9rem}
.practice{max-width:940px;margin:24px 0;border:1px solid #b7cecb;border-top:4px solid var(--accent);border-radius:10px;background:var(--paper);box-shadow:0 8px 24px #173d4b08;padding:30px}.question{font-size:1.2rem;font-weight:550;max-width:780px}.practice-head .tag{border:1px solid #c5dcd2;background:#edf4ee;border-radius:30px;padding:4px 12px}.feedback.correct{background:#e7f3ec;border-color:#167044}.help{background:#f1f5f1;border-radius:6px;padding:5px 16px}.help details{border-top:0}.help details+details{border-top:1px solid var(--line)}.practice button{margin-top:8px}.activity-toolbar{display:flex;gap:12px;flex-wrap:wrap;margin:10px 0}.activity-toolbar button{font-size:.85rem;padding:6px 12px;min-height:44px}.activity-toolbar input{flex-basis:100%;font-size:.8rem}.notes{border-left:3px solid #b7cecb;padding-left:24px}.answer-files a{border-radius:5px;background:#fffefa;border:1px solid #d1dfdc;min-height:52px}.answer-files a:hover{background:#eaf2ee}.answer-files li{margin:0}footer{max-width:1200px;color:#536a73;padding:28px}.physics-diagram{width:100%;max-width:650px;display:block;height:auto}.physics-diagram text{font:17px system-ui;fill:#163c4b}.physics-diagram path,.physics-diagram line{fill:none;stroke:#163c4b;stroke-width:2}.physics-diagram .accent{stroke:#087d80}.physics-diagram .warm{stroke:#a44f2b}
.classroom-only{display:none}.classroom header,.classroom footer,.classroom .notes,.classroom .related,.classroom .breadcrumbs,.classroom #guided-practice,.classroom #report-panel,.classroom #practice-options,.classroom #classroom-enter,.classroom #answer-form,.classroom #feedback{display:none}.classroom .classroom-only{display:inline-block}.classroom main{max-width:1400px}.classroom h1{font-size:2rem}.classroom .practice{max-width:none}.classroom .question{font-size:clamp(1.4rem,3vw,2rem);max-width:none}.classroom .physics-graph,.classroom .instrument-svg,.classroom .physics-diagram{max-width:850px}.classroom .help{font-size:1.3rem}
@media(max-width:1000px){header{flex-wrap:wrap}.topic-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.home-hero{gap:25px}.hero-figure{padding:12px}}
@media(max-width:650px){main{padding:24px 16px 48px}header{padding:15px 16px}header nav{gap:4px 15px}.home-hero{grid-template-columns:1fr;padding-top:0;gap:15px}.home-hero h1{font-size:2.7rem}.hero-figure{display:none}.topic-grid{gap:12px}.topic-card{padding:16px}.topic-card h2{font-size:1.1rem}.route-strip>div+div{border-top:1px solid #c7d8d0;padding-top:12px}.practice{padding:19px}.section-heading{align-items:flex-start}.notes{padding-left:15px}.classroom .question{font-size:1.4rem}}
@media(max-width:380px){.topic-grid{grid-template-columns:1fr}.home-hero h1{font-size:2.4rem}}
@media(prefers-reduced-motion:reduce){.topic-card{transition:none}}
@media print{header,footer,.breadcrumbs,.activity-toolbar,.site-search,.practice-options,#report-panel,button{display:none!important}body,main{background:white;color:black}main{max-width:none;padding:0}.print-question{break-inside:avoid;margin-bottom:20mm}.print-answers{break-before:page}.print-answers article{break-inside:avoid}.print-reference{font-size:9pt;color:#444}}

.visually-hidden{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.guided-step{border-top:1px solid #cbd8dc;margin-top:16px;padding-top:8px}.guided-feedback{font-weight:650}.guided-step h3{font-size:1rem}.working-space{height:90px;border-bottom:1px solid #cbd8dc}.print-question{max-width:850px;margin:30px 0;padding:20px;border:1px solid #cbd8dc;border-radius:8px}.print-answers{border-top:2px solid #087d80;padding-top:24px}.print-controls{max-width:850px}.print-reference{font-size:.8rem;color:#526b73}@media print{.print-controls{display:none!important}.print-question{padding:0;border:0;max-width:none}.print-question h3{margin-bottom:5mm}.print-question .physics-diagram{max-height:48mm}.working-space{height:20mm}.print-reference a{display:none}.print-answers{border:0}}

body:not(.enhanced) .activity-toolbar,body:not(.enhanced) #print-set{display:none}

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.diagram-scroll{overflow:auto;max-width:100%;border:1px solid var(--line)}.diagram-scroll .physics-diagram{width:52rem;min-width:52rem;max-width:none}.diagram-zoom{margin:12px 0}@media print{.diagram-zoom{display:none}}

main{overflow-wrap:anywhere}

/* Acquisition lessons and practical guides. */
.worked-example{border-left:3px solid var(--accent,#247080);padding-left:1rem;margin:1.5rem 0 2rem}.guide-diagram{max-width:34rem;margin:1.5rem auto}.guide-diagram svg{width:100%;height:auto}.guide-diagram text{font-size:16px}.guide-diagram figcaption{font-size:.95rem;margin-top:.5rem}.notes li{margin-bottom:.65rem}.table-scroll{max-width:100%;overflow:auto}.table-scroll:focus-visible{outline:3px solid #247080}.notes table{border-collapse:collapse;width:100%}.notes th,.notes td{padding:.55rem;text-align:left;border-bottom:1px solid #ccd8dc}

.guide-scroll{max-width:100%;overflow:auto}.guide-scroll svg{display:block;width:650px;max-width:none;height:auto}.guide-zoom{margin:1rem 0}@media print{.guide-zoom{display:none}}

.guide-scroll text{font:16px system-ui;fill:currentColor}

.gcse-board-routes{display:grid;gap:12px;margin:24px 0}.gcse-board-routes a{display:block;border-left:4px solid var(--accent);padding:12px 16px;background:#fff;font-weight:700}.gcse-board-routes span{display:block;font-weight:400;font-size:.85rem;color:#47606a;margin-top:5px}.gcse-hero{margin-bottom:36px}.gcse-hero .decorative-image{aspect-ratio:3/2}.gcse-scope{margin-top:32px}.search-filters{border:0;padding:0;margin:20px 0;display:flex;gap:8px 20px;flex-wrap:wrap}.search-filters legend{font-weight:700;margin-bottom:8px}.search-filters label{display:flex;align-items:center;gap:6px;min-height:44px;cursor:pointer}.search-filters input{width:auto;min-height:auto;margin:0;accent-color:var(--accent)}.resource h2 a{text-decoration:underline;text-decoration-thickness:1px;text-underline-offset:3px}.topic-grid{grid-template-columns:repeat(4,minmax(0,1fr))}@media(max-width:1000px){.topic-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:460px){.topic-grid{grid-template-columns:1fr}}
.exam-case {max-width: 54rem}
.exam-part {padding: 1.4rem 0; border-bottom: 1px solid #cbdadb}
.exam-part textarea {width:100%; min-height:7rem; display:block; box-sizing:border-box}
.exam-part input[type="text"] {display:block; width: min(100%, 20rem); box-sizing:border-box; margin: .5rem 0}
.case-option {display:block; padding:.6rem 0}
.case-option input,.rubric-credit,input[name="case-mode"] {width:auto; min-height:auto}
.exam-list div {padding:1rem 0; border-bottom:1px solid #cbdadb}
.exam-list dt {font-weight:700}
.exam-list dd {margin:.3rem 0 0}
.exam-case [hidden] {display:none!important}
@media print {.exam-enhancement,.case-hint {display:none!important} .exam-case #case-rubric {display:block!important} .exam-part textarea {min-height:8rem} .exam-part {break-inside:avoid}}