/* Marine Tools For Students. Scoped, responsive, no external font or runtime dependencies. */
:root{font-family:Inter,"Segoe UI",Arial,sans-serif;color-scheme:dark;background:#071321;color:#e9f4f7;
 --bg:#071321;--panel:#0e2334;--raised:#142e41;--text:#ecf5fa;--muted:#a8c2d3;--border:#28465a;--accent:#63daed;--accent-ink:#041d28;--gold:#e8be78;--good:#91e3bb;--bad:#ffaaa9}
:root[data-theme="bridge"]{--bg:#14100d;--panel:#201911;--raised:#302319;--text:#f7ebd9;--muted:#d6bea7;--border:#5a4633;--accent:#efc685;--accent-ink:#291b0b;--gold:#f8ce8c;--good:#bce1ad;--bad:#ffa99f}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;min-width:0;background:radial-gradient(1200px 500px at 70% -10%,rgba(34,108,136,.16),transparent 70%),var(--bg);color:var(--text);line-height:1.55}
a{color:var(--accent)}
button,input,select{font:inherit}
button,select{cursor:pointer}
button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid var(--gold);outline-offset:3px}
button{min-height:40px}
[hidden]{display:none!important}
.skip-link{position:absolute;left:12px;top:-80px;padding:10px;background:var(--accent);color:var(--accent-ink);z-index:100}
.skip-link:focus{top:12px}
.topbar{height:78px;display:flex;justify-content:space-between;align-items:center;gap:20px;max-width:1280px;margin:auto;padding:0 24px;border-bottom:1px solid var(--border)}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--text)}
.brand img{border-radius:10px;object-fit:cover}
.brand span{display:flex;flex-direction:column;line-height:1.28}
.brand strong{font-size:15px;letter-spacing:.16em}
.brand small{font-size:10px;letter-spacing:.2em;color:var(--muted);margin-top:6px}
.toplinks{display:flex;align-items:center;gap:22px}
.toplinks a{text-decoration:none;color:var(--muted);font-size:13px;font-weight:600}
.toplinks a:hover{color:var(--text)}
main{max-width:1280px;padding:0 24px;margin:auto}
.hero{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(300px,.8fr);gap:42px;align-items:center;padding:68px 0 62px;border-bottom:1px solid var(--border)}
.eyebrow{color:var(--accent);text-transform:uppercase;letter-spacing:.14em;font-size:10px;font-weight:800}
.status-dot,.tiny-dot{display:inline-block;width:8px;height:8px;border-radius:50%;background:var(--good);margin-right:8px}
.hero h1{font-size:clamp(34px,4.6vw,62px);font-weight:740;letter-spacing:-.055em;line-height:1.07;max-width:740px;margin:16px 0 16px}
.hero p{color:var(--muted);max-width:620px;font-size:16px;line-height:1.75}
.hero .preview-note{font-size:12px;margin:24px 0 0;color:var(--muted)}
.hero-buttons{display:flex;gap:12px;flex-wrap:wrap;margin-top:28px}
.main-btn,.outline-btn{display:inline-flex;align-items:center;justify-content:center;gap:9px;min-height:44px;padding:10px 17px;border-radius:10px;font-weight:700;font-size:13px;text-decoration:none}
.main-btn{background:var(--accent);border:1px solid var(--accent);color:var(--accent-ink)}
.outline-btn{background:transparent;color:var(--text);border:1px solid var(--border)}
.main-btn:hover{filter:brightness(1.09)}
.outline-btn:hover{background:var(--raised)}
.hero-aside{background:linear-gradient(150deg,var(--raised),var(--panel));border:1px solid var(--border);border-radius:18px;box-shadow:0 16px 45px rgba(0,0,0,.15);overflow:hidden}
.aside-head{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:17px 19px;border-bottom:1px solid var(--border);font-size:11px;letter-spacing:.1em}
.live-tag{border:1px solid var(--border);padding:4px 8px;border-radius:6px;color:var(--good);font-size:9px}
.stats-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr))}
.stats-grid>div{min-height:117px;padding:24px;border-right:1px solid var(--border);border-bottom:1px solid var(--border);display:flex;flex-direction:column;gap:10px}
.stats-grid b{font-size:34px;font-weight:720;line-height:1}
.stats-grid small{font-size:10px;letter-spacing:.06em;color:var(--muted)}
.aside-foot{padding:15px 20px;color:var(--muted);font-size:12px}
.workspace{padding:40px 0 70px}
.workspace-top{display:flex;align-items:flex-end;justify-content:space-between;gap:20px;flex-wrap:wrap;margin-bottom:25px}
.workspace-top h2{font-size:29px;line-height:1.2;margin:6px 0 0;letter-spacing:-.03em}
.selectors{display:flex;gap:12px;flex-wrap:wrap}
.selectors label{display:flex;flex-direction:column;color:var(--muted);font-size:11px;gap:5px}
select,input{border:1px solid var(--border);background:var(--raised);color:var(--text);border-radius:9px;min-height:43px;padding:10px 12px;min-width:0}
select option{background:var(--panel);color:var(--text)}
.tabs{display:flex;border-bottom:1px solid var(--border);gap:4px;overflow-x:auto;scrollbar-width:thin}
.tabs button{white-space:nowrap;border:0;border-bottom:2px solid transparent;background:transparent;color:var(--muted);padding:13px 18px;margin:0;font-weight:650}
.tabs button.active{color:var(--accent);border-color:var(--accent)}
.tabs button:hover{color:var(--text)}
.controls{display:flex;align-items:center;gap:14px;flex-wrap:wrap;padding:26px 0 22px}
.filter-select{display:flex;flex:1 1 205px;min-width:0;flex-direction:column;gap:5px;color:var(--muted);font-size:12px}
.filter-select select{width:100%;max-width:none!important;min-height:44px;flex:0 0 auto!important}
.controls .search-field{align-self:end}
.controls .saved-check{align-self:end;min-height:44px}
.chapter-context{padding:10px 14px;border:1px solid var(--border);border-radius:9px;color:var(--muted);font-size:13px;display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}
.search-field{display:flex;align-items:center;gap:10px;flex:1 1 330px;min-width:0;background:var(--raised);border:1px solid var(--border);border-radius:10px;padding:0 14px}
.search-field span{font-size:21px;color:var(--muted)}
.search-field input{flex:1;border:0;background:transparent;outline:0;padding:12px 3px;width:100%}
.search-field:focus-within{outline:3px solid var(--accent);outline-offset:1px}
#topic-filter{max-width:250px;flex:1 1 190px}
.saved-check{display:flex;align-items:center;gap:8px;color:var(--muted);font-size:13px;white-space:nowrap}
.saved-check input{min-height:18px;width:18px;accent-color:var(--accent)}
.section-line{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:2px 0 20px}
.section-line p{margin:0;color:var(--muted);font-size:12px}
.quiet-button{background:transparent;border:1px solid transparent;color:var(--muted);font-size:12px;padding:7px 10px;border-radius:8px}
.quiet-button:hover{border-color:var(--border);color:var(--text)}
.formula-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}
.formula-card,.calc-card,.exercise-card,.resource-card{background:var(--panel);border:1px solid var(--border);border-radius:13px;min-width:0}
.formula-card{display:flex;flex-direction:column;padding:20px;min-height:244px}
.card-line{display:flex;align-items:center;justify-content:space-between;gap:10px}
.topic-pill{display:inline-flex;font-size:10px;letter-spacing:.04em;background:var(--raised);border:1px solid var(--border);color:var(--accent);padding:5px 9px;border-radius:7px;max-width:100%;overflow-wrap:anywhere}
.card-line button{border:0;background:transparent;color:var(--gold);font-size:22px;line-height:1;min-height:30px;padding:2px 5px}
.formula-card h3{font-size:16px;line-height:1.3;margin:13px 0}
.equation{background:var(--raised);color:var(--text);font:600 16px/1.6 "Cambria Math","STIX Two Math",Georgia,serif;border-radius:8px;padding:12px;overflow-x:auto;overflow-wrap:anywhere;min-height:54px}
.formula-card p{font-size:12px;line-height:1.6;color:var(--muted);margin:12px 0 15px;flex:1}
.card-actions{display:flex;gap:8px;flex-wrap:wrap}
.card-actions button{color:var(--text);border:1px solid var(--border);border-radius:8px;background:var(--raised);font-size:11px;font-weight:700;min-height:34px;padding:5px 9px}
.card-actions button:hover{border-color:var(--accent)}
.load-row{display:flex;justify-content:center;margin-top:26px}
.placeholder{grid-column:1/-1;text-align:center;color:var(--muted);padding:40px}
.section-intro{margin:25px 0 24px}.section-intro h3{font-size:22px;letter-spacing:-.025em;margin:0 0 5px}.section-intro p{font-size:13px;color:var(--muted);max-width:760px;margin:0}
.calc-layout{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:18px}
.calc-card{padding:24px}
.calc-card h3{font-size:22px;margin:24px 0 6px;line-height:1.25}
.calc-card>p{color:var(--muted);font-size:13px;line-height:1.6}
.select-label{display:block;color:var(--muted);font-size:12px;font-weight:700;margin:0 0 8px}
#calc-selector{width:100%}
.calc-fields{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px;margin:22px 0}
.field{display:flex;flex-direction:column;gap:7px;font-size:12px;color:var(--muted)}
.field small{color:var(--accent)}
.field input{width:100%;font-weight:650;font-size:16px}
.calc-card .helper{font-size:12px;color:var(--muted)}
.calc-output{background:var(--raised);border:1px solid var(--border);border-radius:11px;min-height:166px;padding:27px 21px;display:flex;flex-direction:column;justify-content:center}
.calc-output strong{font-size:clamp(26px,3.2vw,42px);line-height:1.2;margin:13px 0 2px;overflow-wrap:anywhere}
.calc-output strong small{font-size:16px;font-weight:500;color:var(--muted)}
.calc-output .warning,.warning{color:var(--gold);font-size:12px}
#working-toggle{margin:19px 0}
.steps{background:var(--raised);border:1px solid var(--border);border-radius:11px;padding:13px 18px;margin:0 0 18px;overflow-wrap:anywhere}
.steps:empty{display:none}
.steps ol{margin:0;padding-left:21px}
.steps li{color:var(--text);padding:6px 0;font-size:13px}
.exercise-card{max-width:830px;margin:0 auto;padding:28px}
.exercise-meta{display:flex;align-items:center;justify-content:space-between;gap:10px;color:var(--muted);font-size:12px}
.exercise-card h3{font-size:clamp(19px,2.5vw,28px);line-height:1.45;letter-spacing:-.02em;margin:25px 0}
.exercise-entry label{display:block;font-size:12px;color:var(--muted);margin-bottom:8px}
.answer-field{display:flex;align-items:center;max-width:330px;background:var(--raised);border:1px solid var(--border);border-radius:8px;overflow:hidden}
.answer-field input{border:0;background:transparent;flex:1;width:100%;font-size:18px}
.answer-field span{padding:5px 11px;color:var(--muted);font-size:12px}
#exercise-feedback{font-size:13px;min-height:20px}
.correct{color:var(--good)}.error{color:var(--bad);font-size:13px}
.exercise-actions{display:flex;gap:12px;flex-wrap:wrap;margin:14px 0 25px}
.exercise-footer{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;border-top:1px solid var(--border);padding-top:19px;color:var(--muted);font-size:12px}
.exercise-footer strong{color:var(--text)}.exercise-nav{display:flex;gap:8px}
.subtle{display:block;margin:18px auto 0}
.resource-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}
.resource-card{padding:22px;display:flex;flex-direction:column}
.resource-card h3{font-size:17px;line-height:1.35;margin:15px 0 8px}
.resource-card p{color:var(--muted);font-size:13px;flex:1}
.resource-card a{font-size:12px;font-weight:700;margin:10px 0}
.resource-card small{color:var(--muted);font-size:11px;line-height:1.5;border-top:1px solid var(--border);padding-top:12px}
footer{border-top:1px solid var(--border);max-width:1280px;margin:auto;padding:26px 24px 36px;color:var(--muted);display:flex;gap:18px;flex-wrap:wrap;align-items:center;font-size:11px}
footer span{margin-right:auto}
footer a{font-size:11px;text-decoration:none;color:var(--muted)}
@media(max-width:1000px){.formula-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.resource-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.hero{grid-template-columns:1fr}.hero-aside{max-width:620px}}
@media(max-width:680px){.topbar{padding:0 15px;height:72px}.brand strong{font-size:12px}.brand small{font-size:9px}.toplinks{gap:8px}.toplinks a{font-size:11px}main{padding:0 16px}.hero{padding:40px 0}.hero h1{font-size:36px}.hero p{font-size:14px}.workspace{padding:29px 0 45px}.workspace-top{align-items:start}.selectors{width:100%}.selectors label{flex:1}.selectors select{width:100%}.tabs button{padding:12px 14px;font-size:12px}.controls{gap:10px}.search-field{flex-basis:100%}#topic-filter{max-width:none}.formula-grid{grid-template-columns:1fr}.formula-card{min-height:0}.calc-layout{grid-template-columns:1fr}.calc-card{padding:18px}.exercise-card{padding:20px}.resource-grid{grid-template-columns:1fr}}
@media(max-width:400px){.calc-fields{grid-template-columns:1fr}.toplinks a:first-child{display:none}.hero-buttons .main-btn,.hero-buttons .outline-btn{width:100%}.stats-grid>div{padding:15px}.formula-card{padding:16px}.exercise-actions button{flex:1 1 100%}}
@media print{html,body{background:#fff!important;color:#000!important;color-scheme:light}.topbar,.hero,.selectors,.tabs,.controls,.load-row,footer,.formula-actions,.card-actions,.section-line button{display:none!important}.workspace{padding:0}.formula-grid{display:block}.formula-card{break-inside:avoid;border:1px solid #ccc;background:#fff;color:#000;margin:0 0 12px;padding:12px}.formula-card h3,.formula-card p,.equation{color:#000!important;background:#fff}.formula-card{min-height:0}.card-line button{display:none}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}

/* Study v2: authored formula guides, discipline filters, practice and print sheet */
#study-group{flex:1 1 175px;max-width:255px}
.formula-explanation{border-top:1px solid var(--border);margin-top:12px;padding-top:11px;font-size:12px}
.formula-explanation summary{cursor:pointer;font-weight:700;color:var(--accent);padding:4px 0;line-height:1.6}
.formula-explanation summary:focus-visible{outline:2px solid var(--gold);outline-offset:4px}
.explanation-body{padding:11px 0 0}
.explanation-body h4{margin:0 0 11px;font-size:13px;letter-spacing:.02em}
.symbol-grid{display:grid;gap:0;border:1px solid var(--border);border-radius:10px;overflow:hidden}
.symbol-grid>div{display:grid;grid-template-columns:minmax(65px,.55fr) minmax(0,2fr) minmax(65px,.8fr);align-items:center;gap:11px;padding:9px 10px;border-bottom:1px solid var(--border)}
.symbol-grid>div:last-child{border-bottom:0}
.symbol-grid code{color:var(--accent);font-size:13px;font-family:"Cambria Math",Consolas,monospace}
.symbol-grid span{color:var(--text);min-width:0}
.symbol-grid small{color:var(--muted);overflow-wrap:anywhere;font-size:11px}
.annotation-pending{font-size:12px;color:var(--muted);margin:8px 0}
.source-status{border-top:1px solid var(--border);margin-top:12px;padding-top:12px;color:var(--muted);font-size:11px;line-height:1.6}
.source-status strong{color:var(--text)}.source-status p{font-size:11px;margin:7px 0 0}
.study-diagram{max-width:390px;margin:14px auto;padding:8px;background:var(--raised);border-radius:10px;color:var(--text)}
.study-diagram svg{width:100%;height:auto;max-height:210px}
.study-diagram svg text{fill:var(--text);font-size:13px;font-family:Inter,"Segoe UI",sans-serif}
.practice-controls{display:flex;flex-wrap:wrap;gap:15px;margin:18px 0}
.practice-controls label{display:flex;flex-direction:column;gap:6px;font-size:12px;color:var(--muted);min-width:min(230px,100%);max-width:100%}
.practice-controls select{width:100%;max-width:320px}
.exercise-meta{flex-wrap:wrap}
.study-hint{margin:14px 0;padding:13px 16px;border:1px solid var(--border);border-left:3px solid var(--accent);background:var(--raised);color:var(--text);border-radius:9px;font-size:13px}
#show-solution:disabled{cursor:not-allowed;opacity:.45}
#show-solution:disabled::after{content:" · Attempt first";font-size:10px}
.sheet-toolbar{display:flex;align-items:center;flex-wrap:wrap;gap:12px;margin:24px 0}
.sheet-toolbar>span{color:var(--muted);font-size:13px;margin-right:auto}
.sheet-formulas{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}
.sheet-card{min-height:0}
.sheet-card .formula-explanation{border-top:1px solid var(--border)}
.sheet-card .source-status{margin-bottom:4px}
@media(max-width:850px){.sheet-formulas{grid-template-columns:1fr}#study-group{max-width:none}}
@media(max-width:480px){.symbol-grid>div{grid-template-columns:minmax(60px,.8fr) 1.7fr;gap:6px}.symbol-grid small{grid-column:2}.practice-controls{flex-direction:column}.practice-controls label{min-width:0}.sheet-toolbar button{flex:1 1 100%}}
@media print{
 .formula-explanation summary,.formula-explanation .source-status a,.card-line button{display:none!important}
 .formula-explanation .explanation-body{display:block!important}
 .formula-explanation .symbol-grid,.source-status{border-color:#ccc!important}
 .study-diagram{background:#fff!important;color:#000!important}
 .study-diagram svg text{fill:#000!important}
 body.print-sheet .workspace-top,body.print-sheet .section-line,body.print-sheet [data-pane]:not([data-pane="sheet"]),body.print-sheet .sheet-toolbar,body.print-sheet .section-intro{display:none!important}
 body.print-sheet [data-pane="sheet"]{display:block!important}
 body.print-sheet .sheet-formulas{display:block}
 body.print-sheet .sheet-card{border:1px solid #bbb;margin:0 0 10px}
 body.print-sheet .symbol-grid>div{color:#000!important}
 body.print-sheet .source-status,body.print-sheet .symbol-grid span,body.print-sheet .symbol-grid small,body.print-sheet .formula-explanation summary{color:#111!important}
}

/* Context-aware symbol index; meaning and units remain tied to formula identity. */
.symbol-review-count{font-size:12px;color:var(--muted);line-height:1.6;margin:14px 0}
.symbol-results{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:16px}
.symbol-context{display:flex;align-items:flex-start;gap:14px;background:var(--panel);border:1px solid var(--border);border-radius:14px;padding:17px;min-width:0}
.symbol-glyph{display:flex;align-items:center;justify-content:center;flex:none;min-width:58px;min-height:52px;padding:5px 8px;border-radius:9px;background:var(--raised);color:var(--accent);font:700 23px "Cambria Math",serif}
.symbol-context-body{min-width:0;font-size:13px}.symbol-context-body strong{font-size:14px}.symbol-context-body p{color:var(--muted);margin:6px 0}.symbol-context-body small{font-size:11px;color:var(--text)}.symbol-context-body .source-state{font-size:11px;color:var(--muted);line-height:1.55;margin:10px 0}.symbol-context-body button{font-size:11px;margin-top:3px}
@media(max-width:740px){.symbol-results{grid-template-columns:1fr}}
@media print{[data-pane="symbols"]{display:none!important}}

.related-equations{margin:18px 0;padding:12px;border:1px solid var(--border,#29495e);border-radius:10px}.related-expression{padding:14px 0;border-bottom:1px solid var(--border,#29495e)}.related-expression:last-child{border:0}.related-expression h5{font-size:14px;margin:4px 0 10px}.source-correction{border-left:3px solid #f8ce81;padding-left:10px}.related-expression .equation{overflow-wrap:anywhere}

/* Consolidated symbol meanings with formula-local evidence underneath. */
.symbol-filters{display:grid;grid-template-columns:minmax(0,1fr) minmax(180px,.4fr);gap:14px;align-items:end}
.symbol-filters>label:last-child{font-size:12px;color:var(--muted)}
.symbol-filters select{display:block;width:100%;margin-top:6px;background:var(--raised);color:var(--text);border:1px solid var(--border);padding:12px;border-radius:10px}
.symbol-context-body{width:100%}.symbol-context-body h4{font-size:16px;margin:1px 0 9px;line-height:1.4}
.symbol-references{margin-top:15px;border-top:1px solid var(--border);padding-top:12px}
.symbol-references summary{cursor:pointer;color:var(--accent);font-weight:600}
.symbol-references ul{list-style:none;padding:0;margin:12px 0 0}.symbol-references>ul>li{padding:12px 0;border-top:1px solid var(--border)}
.symbol-references li li{padding:9px 0 9px 12px;border-left:2px solid var(--border);margin:8px 0}
.symbol-references small{display:block;line-height:1.5;overflow-wrap:anywhere}
.symbol-formula-link,.symbol-variant-link{border:0;border-radius:0;padding:0;text-align:left;background:transparent;color:var(--accent);text-decoration:underline;text-underline-offset:3px}
.symbol-context-body .symbol-formula-link{font-size:13px;font-weight:700}.symbol-context-body .symbol-variant-link{font-size:12px}
.symbol-context{align-self:start}.related-expression[tabindex="-1"]{scroll-margin-top:25px}
@media(max-width:600px){.symbol-filters{grid-template-columns:1fr}.symbol-context{padding:14px;gap:10px}.symbol-glyph{min-width:44px}}

.symbol-evidence{margin-top:8px}.symbol-evidence>summary{font-size:11px;color:var(--muted);font-weight:400}.symbol-results>.symbol-context:only-child{grid-column:1/-1;max-width:900px;width:100%}

.source-open-model{border-left:3px solid var(--gold,#f8ce81);padding:9px 12px;background:#7d54151a;color:var(--text);font-size:12px;line-height:1.6}

/* Reference cases stay beside their source-specific assumptions and units. */
.worked-example{margin:14px 0;border:1px solid var(--border);border-radius:10px;background:var(--raised)}
.worked-example>summary{padding:12px;cursor:pointer;color:var(--accent);font-size:13px;font-weight:700;overflow-wrap:anywhere}
.worked-example>summary:focus-visible{outline:2px solid var(--accent);outline-offset:3px;border-radius:8px}
.worked-example-body{padding:0 14px 12px;overflow-wrap:anywhere;line-height:1.6}
.worked-example h6{font-size:13px;margin:14px 0 6px}.worked-example ul{padding-left:20px;margin:6px 0}
.worked-example .worked-scope{font-size:11px;color:var(--muted)}.worked-result{border-top:1px solid var(--border);padding-top:10px}
@media print{.worked-example{break-inside:avoid}}

.worked-case-label{display:block;padding-top:10px;font-size:12px;color:var(--muted)}
.worked-case-select{display:block;max-width:100%;width:100%;min-height:44px;margin:5px 0 12px;padding:9px;background:var(--base,#071725);color:var(--text);border:1px solid var(--border);border-radius:8px;font:inherit}
.worked-case-select:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

@media(max-width:680px){.formula-grid{display:block}.formula-grid>.formula-card{margin-bottom:14px}}