:root{--navy:#102b3f;--navy2:#173e55;--cream:#f5f0e6;--paper:#fffdf8;--teal:#177c7a;--teal2:#0c5c5b;--copper:#b66b3d;--ink:#17232c;--muted:#596773;--line:#d8ddd9;--good:#166534;--bad:#991b1b;--shadow:0 18px 50px rgba(16,43,63,.10);--radius:18px;--max:1180px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.62}a{color:var(--teal2);text-decoration-thickness:.08em;text-underline-offset:.16em}a:hover{color:var(--copper)}button,input,select,textarea{font:inherit}button{cursor:pointer}.shell{width:min(calc(100% - 36px),var(--max));margin-inline:auto}.narrow{max-width:850px}.skip-link{position:absolute;left:-999px;top:8px;background:#fff;padding:10px;z-index:100}.skip-link:focus{left:8px}.site-header{position:sticky;top:0;z-index:30;background:rgba(255,253,248,.94);backdrop-filter:blur(16px);border-bottom:1px solid rgba(16,43,63,.1)}.header-inner{min-height:78px;display:flex;align-items:center;justify-content:space-between;gap:24px}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--navy)}.brand:hover{color:var(--navy)}.brand-mark{display:grid;place-items:center;width:46px;height:46px;border-radius:14px;background:var(--navy);color:var(--cream);font-weight:800;letter-spacing:.03em;box-shadow:inset 0 -5px 0 rgba(177,107,61,.3)}.brand strong,.brand small{display:block}.brand small{font-size:.75rem;color:var(--muted);font-weight:500}.main-nav{display:flex;align-items:center;gap:4px}.main-nav a{padding:9px 11px;border-radius:9px;text-decoration:none;color:var(--navy);font-size:.94rem;font-weight:650}.main-nav a:hover,.main-nav a[aria-current=page]{background:#e9f2ef;color:var(--teal2)}.nav-toggle{display:none;background:none;border:1px solid var(--line);border-radius:9px;padding:7px 10px}.hero{background:linear-gradient(135deg,var(--navy) 0%,#143b50 72%,#1c4c56 100%);color:white;padding:84px 0 76px;position:relative;overflow:hidden}.hero:after{content:"";position:absolute;width:430px;height:430px;border:1px solid rgba(245,240,230,.14);border-radius:50%;right:-130px;top:-210px;box-shadow:0 0 0 55px rgba(245,240,230,.035),0 0 0 110px rgba(245,240,230,.025)}.hero-grid{display:grid;grid-template-columns:1.45fr .75fr;gap:70px;align-items:center;position:relative;z-index:1}.hero h1,.page-hero h1{font-family:Georgia,"Times New Roman",serif;line-height:1.05;letter-spacing:-.035em;margin:.18em 0 .35em}.hero h1{font-size:clamp(2.6rem,5vw,5rem);max-width:820px}.lede{font-size:clamp(1.08rem,2vw,1.34rem);max-width:780px;color:inherit;opacity:.9}.eyebrow{margin:0 0 8px;text-transform:uppercase;letter-spacing:.14em;font-size:.77rem;font-weight:800;color:var(--copper)}.hero .eyebrow{color:#f0ae7e}.button-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:28px}.button-row.compact{margin-top:14px}.button{display:inline-flex;align-items:center;justify-content:center;min-height:46px;padding:10px 18px;border:1px solid transparent;border-radius:11px;text-decoration:none;font-weight:750;transition:.18s transform,.18s background,.18s border-color}.button:hover{transform:translateY(-1px)}.button.primary{background:var(--teal);color:white}.button.primary:hover{background:var(--teal2);color:white}.button.secondary{background:transparent;border-color:#9fb2b8;color:var(--navy)}.hero .button.secondary{border-color:rgba(255,255,255,.42);color:white}.hero-panel{background:rgba(255,255,255,.09);border:1px solid rgba(255,255,255,.2);padding:28px;border-radius:var(--radius);backdrop-filter:blur(10px)}.hero-panel .label,.tag{display:inline-block;background:#e7f3ef;color:var(--teal2);border-radius:999px;padding:4px 9px;font-size:.75rem;font-weight:800;letter-spacing:.04em}.hero-panel h2{font-family:Georgia,serif;font-size:2rem;margin:.45em 0}.hero-panel a{color:#fff;font-weight:750}.page-hero{background:var(--cream);padding:58px 0;border-bottom:1px solid #e1d9ca}.page-hero h1{font-size:clamp(2.3rem,4.6vw,4.2rem);color:var(--navy);max-width:920px}.page-hero .lede{color:var(--muted)}.section{padding:70px 0}.section-tint{background:#eef4f1}.section-heading{display:flex;justify-content:space-between;gap:40px;align-items:end;margin-bottom:28px}.section-heading h2,.split-callout h2,.prose h2{font-family:Georgia,serif;color:var(--navy);font-size:clamp(1.8rem,3vw,2.7rem);line-height:1.15;margin:0}.section-heading>p{max-width:560px;color:var(--muted)}.card-grid{display:grid;gap:18px}.card-grid.four{grid-template-columns:repeat(4,1fr)}.card-grid.three{grid-template-columns:repeat(3,1fr)}.card{display:block;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:0 5px 18px rgba(16,43,63,.045);text-decoration:none;color:var(--ink);transition:.2s transform,.2s box-shadow,.2s border-color}.card:hover{transform:translateY(-3px);box-shadow:var(--shadow);border-color:#aebfba;color:var(--ink)}.card h2,.card h3{color:var(--navy);margin:.55em 0 .35em;line-height:1.2}.card p{color:var(--muted);margin-bottom:0}.card-link{display:block;margin-top:18px;color:var(--teal2);font-weight:750}.tool-icon{display:grid;place-items:center;width:44px;height:44px;border-radius:12px;background:var(--navy);color:var(--cream);font-weight:800}.split-callout{display:flex;justify-content:space-between;align-items:center;gap:40px}.prose{font-size:1.04rem}.prose h2{margin-top:1.5em}.prose li{margin:.5em 0}.notice{padding:18px 20px;border-left:4px solid var(--copper);background:#fff7ef;border-radius:0 12px 12px 0;color:var(--ink)}.interactive{background:#fff;border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:clamp(20px,4vw,38px)}.generator-card.wide{max-width:1060px;margin:auto}.generator-toolbar{display:flex;justify-content:space-between;gap:18px;align-items:end;border-bottom:1px solid var(--line);padding-bottom:20px;margin-bottom:25px}.generator-toolbar label{display:grid;gap:6px;color:var(--muted);font-size:.9rem;font-weight:700}.generator-toolbar select{min-width:210px;padding:9px 12px;border:1px solid #acb6ba;border-radius:9px;background:#fff;color:var(--ink)}.question-box{background:#f2f6f4;border-radius:14px;padding:22px;margin:18px 0}.question-box h2{margin-top:0;color:var(--navy)}.data-table{width:100%;border-collapse:collapse;margin:18px 0;background:white}.data-table th,.data-table td{border:1px solid #cfd8d5;padding:10px;text-align:center}.data-table th{background:#e8f0ed;color:var(--navy)}.answer-form,.multi-answer{display:flex;gap:14px;align-items:end;flex-wrap:wrap;margin:22px 0}.answer-form label,.multi-answer label,.contact-form label{display:grid;gap:6px;font-weight:700;color:var(--navy)}.answer-form label{grid-template-columns:1fr auto;align-items:end}.answer-form label>span{padding-bottom:10px}.answer-form input,.multi-answer input,.contact-form input,.contact-form textarea{border:1px solid #9eaaae;border-radius:10px;padding:10px 12px;min-width:170px;background:#fff;color:var(--ink)}.answer-form label>input{grid-row:2;grid-column:1}.answer-form label>span{grid-row:2;grid-column:2}.multi-answer label{flex:1;min-width:180px}.feedback-panel,.solution-panel{margin-top:16px;border-radius:12px;padding:0;overflow:hidden}.feedback-panel:not(:empty),.solution-panel:not([hidden]){padding:16px 18px}.feedback-panel.good{background:#ecf8ef;color:var(--good);border:1px solid #b9dfc1}.feedback-panel.bad{background:#fff0f0;color:var(--bad);border:1px solid #efc1c1}.feedback-panel.neutral,.solution-panel{background:#f2f5f4;color:var(--ink);border:1px solid #d6dfdc}.solution-panel ol{margin-bottom:0}.text-button{border:0;background:none;color:var(--teal2);font-weight:750;padding:7px 3px;text-decoration:underline;text-underline-offset:3px}.option-stack{display:grid;gap:10px;margin-top:20px}.option-stack button{background:white;text-align:left;border:1px solid #aebbb8;border-radius:11px;padding:13px 15px}.option-stack button:hover{background:#eef6f3}.quiz-shell .quiz-progress{display:flex;justify-content:space-between;gap:20px;color:var(--muted);font-size:.9rem}.progress-track{height:8px;background:#e6ece9;border-radius:999px;overflow:hidden;margin:8px 0 24px}.progress-track span{display:block;height:100%;background:var(--teal);transition:width .25s}.statement-card{background:var(--navy);color:white;border-radius:16px;padding:28px;margin:18px 0}.statement-card h2{margin:0;font-family:Georgia,serif;font-size:clamp(1.35rem,3vw,2rem);line-height:1.36}.choice-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}.choice-row button{border:2px solid #9eaeaa;background:#fff;border-radius:13px;padding:16px;font-weight:800;color:var(--navy)}.choice-row button:hover{border-color:var(--teal);background:#eef7f4}.quiz-controls{display:flex;justify-content:space-between;gap:15px;align-items:center;margin-top:20px}.score-pills{display:flex;gap:8px;flex-wrap:wrap}.score-pills span{background:#edf2f0;border-radius:999px;padding:5px 9px;font-size:.84rem}.audit-form fieldset{border:0;border-bottom:1px solid var(--line);padding:10px 0 22px;margin-bottom:18px}.audit-form legend{font-weight:800;color:var(--navy);margin-bottom:12px}.audit-form label{display:block;margin:8px 0}.contact-form{display:grid;gap:16px}.contact-form textarea{resize:vertical}.honeypot{position:absolute!important;left:-9999px!important}.sim-controls{display:grid;grid-template-columns:1fr 1fr;gap:24px}.sim-controls label{display:grid;grid-template-columns:1fr auto;gap:8px;font-weight:700}.sim-controls input{grid-column:1/3;width:100%}canvas{display:block;max-width:100%;height:auto;background:#fff;border:1px solid var(--line);border-radius:12px;margin:24px 0}.site-footer{background:var(--navy);color:#d9e2e4;padding:52px 0 24px;margin-top:40px}.footer-grid{display:grid;grid-template-columns:2fr 1fr;gap:40px}.footer-grid p{max-width:620px;color:#bac8cc}.footer-grid nav{display:grid;align-content:start;gap:8px}.footer-grid a{color:#e9f1ef}.footer-small{border-top:1px solid rgba(255,255,255,.15);padding-top:20px;margin-top:30px;font-size:.85rem;color:#9fb1b5}@media(max-width:900px){.main-nav{display:none;position:absolute;top:70px;left:18px;right:18px;background:white;border:1px solid var(--line);border-radius:14px;padding:10px;box-shadow:var(--shadow);flex-direction:column;align-items:stretch}.main-nav.open{display:flex}.nav-toggle{display:block}.hero-grid{grid-template-columns:1fr;gap:35px}.card-grid.four,.card-grid.three{grid-template-columns:repeat(2,1fr)}.section-heading{align-items:start;flex-direction:column}.split-callout{align-items:start;flex-direction:column}}@media(max-width:620px){.shell{width:min(calc(100% - 24px),var(--max))}.brand small{display:none}.hero{padding:58px 0}.section{padding:48px 0}.card-grid.four,.card-grid.three{grid-template-columns:1fr}.choice-row{grid-template-columns:1fr}.generator-toolbar,.answer-form,.multi-answer{align-items:stretch;flex-direction:column}.answer-form label{width:100%}.answer-form input,.multi-answer input{width:100%;min-width:0}.sim-controls{grid-template-columns:1fr}.footer-grid{grid-template-columns:1fr}.page-hero{padding:42px 0}}


/* Temporary staging marker */
.staging-banner {
    position: relative;
    z-index: 1000;
    padding: 0.55rem 1rem;
    text-align: center;
    background: #fff3cd;
    color: #4b3b00;
    border-bottom: 1px solid #d9bd62;
    font-size: 0.92rem;
}

/* v0.2 content recovery and richer practice interfaces */
.legacy-intro-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(360px,.9fr);gap:48px;align-items:center}.legacy-figure{margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:10px;box-shadow:var(--shadow)}.legacy-figure img{display:block;width:100%;height:auto;border-radius:12px}.legacy-figure figcaption{padding:10px 8px 4px;color:var(--muted);font-size:.88rem}.bt-studio{padding:0;overflow:hidden}.app-tabs{display:flex;gap:0;border-bottom:1px solid var(--line);background:#f5f7f6}.app-tab{flex:1;border:0;border-right:1px solid var(--line);padding:17px 20px;background:transparent;color:var(--muted);font-weight:800}.app-tab:last-child{border-right:0}.app-tab:hover{background:#eef5f2;color:var(--navy)}.app-tab.active{background:#fff;color:var(--teal2);box-shadow:inset 0 -3px 0 var(--teal)}.app-panel{padding:clamp(22px,4vw,38px)}.bt-toolbar{align-items:end}.bt-toolbar label{flex:1}.bt-toolbar select{width:100%;min-width:170px}.toolbar-actions{display:flex;gap:10px;flex-wrap:wrap}.bt-question-meta{display:flex;gap:8px;flex-wrap:wrap;margin:0 0 10px}.bt-question-meta span{background:#e7f3ef;color:var(--teal2);border:1px solid #c8e0d9;border-radius:999px;padding:5px 10px;font-size:.78rem;font-weight:800}.bt-question-box{border:1px solid #d8e3df;background:linear-gradient(145deg,#f5f9f7,#edf4f1);box-shadow:inset 4px 0 0 var(--teal)}.bt-question-box header{display:flex;align-items:center;justify-content:space-between;gap:20px;flex-wrap:wrap}.bt-question-box header h2{margin:.25rem 0;color:var(--navy)}.question-guidance{background:#fff8ef;border-left:3px solid var(--copper);padding:10px 13px;border-radius:0 8px 8px 0}.equation-strip{display:flex;gap:12px;flex-wrap:wrap;margin-top:18px}.equation-strip span{background:#fff;border:1px solid #c8d4d0;border-radius:9px;padding:8px 11px;font-family:"Source Code Pro",ui-monospace,monospace;font-size:.92rem}.bt-answer-form{margin-bottom:4px}.field-help{margin:0;color:var(--muted);font-size:.88rem}.bt-help-buttons{border-top:1px solid var(--line);padding-top:12px}.hint-label{margin:0;text-transform:uppercase;letter-spacing:.1em;font-size:.75rem;font-weight:800;color:var(--copper)}.worked-steps li{margin:.75rem 0}.method-steps{counter-reset:method;list-style:none;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}.method-steps li{counter-increment:method;background:#f4f7f5;border:1px solid var(--line);border-radius:14px;padding:18px 18px 18px 60px;position:relative;margin:0}.method-steps li:before{content:counter(method);position:absolute;left:17px;top:17px;width:30px;height:30px;border-radius:50%;display:grid;place-items:center;background:var(--navy);color:white;font-weight:850}.two-column-notes{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:28px 0}.practice-set-header{display:flex;justify-content:space-between;gap:30px;align-items:start}.practice-set-header h2{font-family:Georgia,serif;color:var(--navy);font-size:2rem;margin:.2em 0}.practice-questions{display:grid;gap:20px}.answer-key{margin-top:24px;border:1px solid var(--line);border-radius:14px;background:#f8faf9;padding:0 18px}.answer-key summary{cursor:pointer;padding:16px 0;font-weight:800;color:var(--teal2)}.answer-key section{padding:8px 0 18px;border-top:1px solid var(--line)}.print-only{display:none}.tutor-guide{max-width:1000px}.article-intro{margin-bottom:34px}.faq-list{list-style:none;padding:0;counter-reset:faq;display:grid;gap:18px}.faq-item{counter-increment:faq;background:#fff;border:1px solid var(--line);border-radius:16px;padding:24px 26px 24px 78px;position:relative;box-shadow:0 5px 18px rgba(16,43,63,.04)}.faq-item:before{content:counter(faq);position:absolute;left:24px;top:24px;width:38px;height:38px;display:grid;place-items:center;border-radius:12px;background:var(--navy);color:#fff;font-weight:850}.faq-item h2{font-size:clamp(1.25rem,2.1vw,1.65rem);margin:0 0 .55rem}.faq-item p{margin:0;color:#35444f}

/* More game-like quiz presentation without sacrificing accessibility */
.quiz-shell{position:relative}.quiz-start{text-align:center;padding:14px 0 6px}.quiz-start-icon{width:78px;height:78px;margin:0 auto 16px;display:grid;place-items:center;border-radius:24px;background:linear-gradient(145deg,var(--navy),var(--teal2));color:#fff;font-family:Georgia,serif;font-size:1.55rem;box-shadow:0 14px 30px rgba(16,43,63,.22)}.quiz-start h2{font-family:Georgia,serif;color:var(--navy);font-size:2rem;margin:.3rem 0}.quiz-status-row{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap}.quiz-stat-group{display:flex;gap:8px;flex-wrap:wrap}.quiz-stat{background:#edf3f0;border:1px solid #d7e2de;border-radius:999px;padding:5px 10px;font-size:.82rem;color:var(--navy);font-weight:750}.statement-card{position:relative;overflow:hidden;min-height:180px;display:grid;place-items:center;text-align:center}.statement-card:after{content:"";position:absolute;width:180px;height:180px;border-radius:50%;right:-90px;top:-100px;border:1px solid rgba(255,255,255,.16);box-shadow:0 0 0 35px rgba(255,255,255,.035)}.statement-card h2{position:relative;z-index:1}.choice-row button{min-height:76px;display:flex;align-items:center;justify-content:center;gap:10px;font-size:1.1rem;transition:.18s transform,.18s background,.18s border-color}.choice-row button:hover{transform:translateY(-2px)}.choice-row button[data-answer="true"]:before{content:"T";display:grid;place-items:center;width:32px;height:32px;border-radius:10px;background:#e4f5e9;color:var(--good)}.choice-row button[data-answer="false"]:before{content:"F";display:grid;place-items:center;width:32px;height:32px;border-radius:10px;background:#fff0f0;color:var(--bad)}.choice-row button.selected-correct{border-color:#4ca36a;background:#effaf2}.choice-row button.selected-wrong{border-color:#cb6666;background:#fff1f1}.choice-row button:disabled{cursor:default;opacity:.78;transform:none}.feedback-panel.quiz-feedback:not(:empty){font-size:1.02rem}.feedback-explanation{display:block;margin-top:.35rem;color:inherit}.quiz-complete{text-align:center}.quiz-complete .result-ring{--score:0;width:126px;height:126px;border-radius:50%;margin:0 auto 20px;display:grid;place-items:center;background:conic-gradient(var(--teal) calc(var(--score)*1%),#e2e9e6 0);position:relative}.quiz-complete .result-ring:before{content:"";position:absolute;inset:12px;border-radius:50%;background:#fff}.quiz-complete .result-ring strong{position:relative;z-index:1;font-size:1.45rem;color:var(--navy)}

@media(max-width:900px){.legacy-intro-grid{grid-template-columns:1fr}.method-steps{grid-template-columns:1fr}.two-column-notes{grid-template-columns:1fr}}
@media(max-width:620px){.app-tabs{flex-direction:column}.app-tab{border-right:0;border-bottom:1px solid var(--line)}.app-tab:last-child{border-bottom:0}.bt-toolbar,.toolbar-actions{width:100%}.toolbar-actions .button{flex:1}.faq-item{padding:20px 18px 20px 64px}.faq-item:before{left:16px;top:19px}.legacy-intro-grid{gap:26px}}

@media print{
  .site-header,.site-footer,.staging-banner,.page-hero,.legacy-intro-grid,.back-titration-guide,.app-tabs,#bt-single-panel,.generator-toolbar,#bt-print-set{display:none!important}
  body{background:#fff;color:#000;font-size:10.5pt}.section,.section-tint{padding:0;background:#fff}.shell{width:100%;max-width:none}.interactive{border:0;box-shadow:none;padding:0}.app-panel{padding:0}.print-only{display:block}.practice-set-header{border-bottom:2px solid #000;margin-bottom:16px}.practice-set .question-box{break-inside:avoid;background:#fff;border:1px solid #555;box-shadow:none;padding:14px;margin:0 0 14px}.practice-set .equation-strip span{border-color:#777}.answer-key{break-before:page;border:0;padding:0;background:#fff}.answer-key[open] summary{display:none}.answer-key:not([open]){display:none}.practice-set a{color:#000;text-decoration:none}
}
.hub-note{display:inline-block;max-width:820px;margin:10px 0 0;padding:9px 13px;border-radius:10px;background:rgba(255,255,255,.62);border:1px solid #ded6c8;color:#4d5d68;font-size:.94rem}
.study-intro .notice{align-self:center}
.colour-game-header{display:flex;justify-content:space-between;gap:24px;align-items:end;border-bottom:1px solid var(--line);padding-bottom:18px}.colour-game-header h2{margin:.15em 0;color:var(--navy);font-family:Georgia,serif}.colour-game-header label{display:grid;gap:5px;font-weight:750;color:var(--navy)}.colour-game-header select{padding:9px 12px;border:1px solid #aab6b3;border-radius:9px;background:#fff}.colour-stats{margin:16px 0}.colour-prompt{min-height:220px;display:grid;place-items:center;text-align:center;background:linear-gradient(145deg,var(--navy),#174b57);color:#fff;border-radius:18px;padding:30px;position:relative;overflow:hidden}.colour-prompt:after{content:"";position:absolute;width:210px;height:210px;border-radius:50%;right:-110px;top:-110px;border:1px solid rgba(255,255,255,.16);box-shadow:0 0 0 42px rgba(255,255,255,.035)}.colour-prompt>*{position:relative;z-index:1}.colour-prompt h2{font-family:Georgia,serif;font-size:clamp(2rem,5vw,3.4rem);margin:.15em 0}.colour-prompt p{margin:.2em 0;opacity:.9}.colour-context{text-transform:uppercase;letter-spacing:.1em;font-size:.75rem;font-weight:800}.large-swatch{display:block;width:70px;height:70px;border-radius:22px;background:var(--swatch);border:3px solid rgba(255,255,255,.75);box-shadow:0 10px 28px rgba(0,0,0,.22)}.colour-options{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:18px 0}.colour-options button{min-height:74px;text-align:left;display:flex;align-items:center;gap:13px;border:2px solid #aebbb8;background:#fff;border-radius:13px;padding:13px 15px;color:var(--navy);font-weight:800}.colour-options button:hover{border-color:var(--teal);background:#eef7f4;transform:translateY(-1px)}.colour-options button:disabled{cursor:default;transform:none;opacity:.85}.colour-options button.selected-correct{border-color:#4ca36a;background:#effaf2}.colour-options button.selected-wrong{border-color:#cb6666;background:#fff1f1}.colour-chip{flex:0 0 auto;width:38px;height:38px;border-radius:12px;background:var(--swatch);border:1px solid rgba(0,0,0,.18);box-shadow:inset 0 0 0 2px rgba(255,255,255,.22)}.formula-choice{font-family:Georgia,serif;font-size:1.2rem;min-width:115px}.colour-options small{font-weight:550;color:var(--muted)}
@media(max-width:620px){.colour-game-header{align-items:stretch;flex-direction:column}.colour-options{grid-template-columns:1fr}.colour-prompt{min-height:190px}}

/* v0.2 featured recovery card */
.featured-recovery { padding-top: 2rem; padding-bottom: 0; }
.featured-game-card {
    position: relative;
    display: grid;
    grid-template-columns: minmax(0, 1fr) 220px;
    align-items: center;
    gap: 2rem;
    overflow: hidden;
    padding: clamp(1.6rem, 4vw, 3rem);
    border: 1px solid rgba(28, 121, 128, .25);
    border-radius: 26px;
    background: linear-gradient(135deg, #f8f3e8 0%, #edf7f5 62%, #e1eef1 100%);
    color: var(--ink, #153142);
    box-shadow: 0 18px 50px rgba(16, 43, 63, .10);
    text-decoration: none;
}
.featured-game-card h2 { margin: .2rem 0 .65rem; font-size: clamp(1.8rem, 4vw, 3rem); }
.featured-game-card p:not(.eyebrow) { max-width: 58rem; margin-bottom: 1.25rem; }
.featured-game-card .button { display: inline-flex; }
.colour-orbit { position: relative; width: 190px; height: 190px; margin-inline: auto; }
.colour-orbit::before {
    content: '';
    position: absolute;
    inset: 31px;
    border: 2px dashed rgba(16,43,63,.22);
    border-radius: 50%;
}
.colour-orbit span { position: absolute; width: 64px; height: 64px; border-radius: 50%; box-shadow: inset 0 0 0 8px rgba(255,255,255,.45), 0 10px 24px rgba(16,43,63,.16); }
.colour-orbit span:nth-child(1) { background:#174b9a; left:63px; top:0; }
.colour-orbit span:nth-child(2) { background:#d66a22; right:0; top:55px; }
.colour-orbit span:nth-child(3) { background:#6d2f8c; right:27px; bottom:0; }
.colour-orbit span:nth-child(4) { background:#416b45; left:13px; bottom:18px; }
.colour-orbit span:nth-child(5) { background:#e2c51b; left:0; top:43px; }
@media (max-width: 720px) {
    .featured-game-card { grid-template-columns: 1fr; }
    .colour-orbit { width: 150px; height: 150px; order: -1; }
    .colour-orbit span { width: 50px; height: 50px; }
    .colour-orbit span:nth-child(1) { left:50px; }
}

/* v0.3 matching engine */
.matching-shell{max-width:1180px;margin:auto}.matching-start{text-align:center;padding:18px 0}.matching-start-mark{width:76px;height:76px;margin:0 auto 16px;border-radius:24px;display:grid;place-items:center;background:linear-gradient(145deg,var(--navy),var(--teal2));color:#fff;font-size:2rem;font-weight:850;box-shadow:0 14px 30px rgba(16,43,63,.2)}.matching-start h2,.matching-finish h2,.matching-column h2,.kc-studio h2{font-family:Georgia,serif;color:var(--navy)}.matching-start p{max-width:760px;margin:0 auto 22px;color:var(--muted)}.matching-start-controls{display:flex;justify-content:center;align-items:end;gap:14px;flex-wrap:wrap}.matching-start-controls label{display:grid;gap:6px;text-align:left;color:var(--navy);font-weight:750}.matching-start-controls select{min-width:180px;padding:10px 12px;border:1px solid #aebbb8;border-radius:10px;background:#fff}.matching-status-row{display:flex;justify-content:space-between;gap:16px;align-items:center;flex-wrap:wrap}.matching-message{margin:18px 0;padding:12px 15px;border-radius:11px;background:#eef3f1;border:1px solid #d6dfdc;color:var(--navy);font-weight:700;text-align:center}.matching-message.good{background:#edf8f0;border-color:#b8ddc1;color:var(--good)}.matching-message.bad{background:#fff0f0;border-color:#efc3c3;color:var(--bad)}.matching-message.warning{background:#fff8e7;border-color:#ead39a;color:#7a5608}.matching-board{display:grid;grid-template-columns:1fr 1.35fr;gap:18px;align-items:start}.matching-column{border:1px solid var(--line);border-radius:16px;padding:18px;background:#f8faf9}.matching-column h2{margin:.1em 0 .7em;text-align:center;font-size:1.45rem}.matching-list{display:grid;gap:9px}.matching-card{width:100%;border:1px solid #b7c2bf;border-radius:11px;background:#fff;padding:12px 14px;text-align:left;color:var(--ink);font-weight:650;line-height:1.42;transition:.16s transform,.16s border-color,.16s background;display:flex;justify-content:space-between;align-items:center;gap:10px}.matching-card:hover{transform:translateY(-1px);border-color:var(--teal);background:#eef7f4}.matching-card.selected{border:2px solid var(--teal);background:#dff1ec;box-shadow:0 0 0 3px rgba(23,124,122,.12)}.matching-card.matched{background:#edf8f0;border-color:#9bc9a7;color:#31543a;opacity:.62}.matching-count{flex:0 0 auto;padding:3px 7px;border-radius:999px;background:#e8eeec;color:var(--muted);font-size:.72rem}.matching-finish{text-align:center;padding:30px 0 10px}.matching-finish .result-ring{--score:0;width:126px;height:126px;border-radius:50%;margin:0 auto 20px;display:grid;place-items:center;background:conic-gradient(var(--teal) calc(var(--score)*1%),#e2e9e6 0);position:relative}.matching-finish .result-ring:before{content:"";position:absolute;inset:12px;border-radius:50%;background:#fff}.matching-finish .result-ring strong{position:relative;z-index:1;font-size:1.45rem;color:var(--navy)}.shake{animation:matchingShake .4s cubic-bezier(.36,.07,.19,.97) both}@keyframes matchingShake{10%,90%{transform:translateX(-1px)}20%,80%{transform:translateX(2px)}30%,50%,70%{transform:translateX(-4px)}40%,60%{transform:translateX(4px)}}

/* v0.3 isotope generator */
.isotope{font-family:Georgia,"Times New Roman",serif;font-weight:750;white-space:nowrap}.hard-isotope-question .tag{margin-bottom:8px}.math-line{display:inline-block;margin-top:6px;padding:7px 9px;border-radius:8px;background:#e8efed;font-family:Georgia,"Times New Roman",serif;overflow-wrap:anywhere}

/* v0.3 Kc studio */
.kc-studio{max-width:1180px;margin:auto}.app-tabs{display:flex;border:1px solid var(--line);border-radius:13px 13px 0 0;overflow:hidden;background:#eef3f1}.app-tab{flex:1;border:0;border-right:1px solid var(--line);padding:13px 16px;background:transparent;color:var(--navy);font-weight:800}.app-tab:last-child{border-right:0}.app-tab.active{background:var(--navy);color:#fff}.app-panel{padding:26px 4px 4px}.kc-sim-heading{display:flex;justify-content:space-between;gap:24px;align-items:start;margin-bottom:18px}.kc-sim-heading h2{margin:.1em 0 .3em;font-size:clamp(1.55rem,3vw,2.35rem)}.kc-sim-heading p{margin:0;max-width:820px;color:var(--muted)}.tag.active-catalyst{background:#dff3e7;color:#135b31}.kc-control-grid{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:9px;margin:18px 0}.kc-control-grid button{min-height:46px;border:1px solid #aab8b5;border-radius:10px;background:#fff;color:var(--navy);font-weight:750;padding:8px 10px}.kc-control-grid button:hover{background:#eef7f4;border-color:var(--teal)}.kc-control-grid button.active{background:#dfeaf8;border-color:#7e9fc4}.kc-control-grid button.reset{background:#fff2e9;border-color:#d8a17f;color:#7b3f1e}.kc-control-grid button:disabled{opacity:.5;cursor:not-allowed}.kc-sim-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:18px}.kc-visual-panel,.kc-data-panel{border:1px solid var(--line);border-radius:16px;background:#f8faf9;padding:20px}.kc-visual-panel h3,.kc-data-panel h3{margin:.1em 0 1em;color:var(--navy);text-align:center}.kc-bars{height:250px;display:flex;align-items:end;justify-content:space-around;gap:22px;padding:30px 12px 0;border-bottom:2px solid #aab8b5}.kc-bar-wrap{height:100%;flex:1;display:flex;flex-direction:column;justify-content:end;align-items:center;gap:8px}.kc-bar{width:min(82px,72%);min-height:8px;border-radius:11px 11px 0 0;position:relative;transition:height .12s linear;box-shadow:inset 0 0 0 1px rgba(255,255,255,.25)}.kc-bar span{position:absolute;top:-28px;left:50%;transform:translateX(-50%);font-size:.82rem;font-weight:800;color:var(--navy);background:#fff;padding:2px 5px;border-radius:5px;white-space:nowrap}.kc-bar.n2{background:#3f73a8}.kc-bar.h2{background:#4f8b5d}.kc-bar.nh3{background:#bd6a3f}.kc-rate-display{display:flex;justify-content:center;align-items:center;gap:8px;margin:24px 0 12px;color:var(--muted);font-weight:750}.rate-arrow{font-size:1.8rem;display:inline-block}.kc-rate-display[data-direction="forward"] .forward{color:var(--good);animation:rateForward .65s alternate infinite}.kc-rate-display[data-direction="forward"] .reverse{opacity:.35}.kc-rate-display[data-direction="reverse"] .reverse{color:var(--bad);animation:rateReverse .65s alternate infinite}.kc-rate-display[data-direction="reverse"] .forward{opacity:.35}.kc-rate-display[data-direction="equilibrium"] .forward,.kc-rate-display[data-direction="equilibrium"] .reverse{color:var(--teal);animation:ratePulse 1.3s alternate infinite}@keyframes rateForward{to{transform:translateX(5px)}}@keyframes rateReverse{to{transform:translateX(-5px)}}@keyframes ratePulse{to{opacity:.45}}.kc-data-list{display:grid;gap:8px;margin:0}.kc-data-list div{display:flex;justify-content:space-between;gap:18px;padding:9px 0;border-bottom:1px solid #dce3e0}.kc-data-list dt{color:var(--muted)}.kc-data-list dd{margin:0;font-weight:800;color:var(--navy)}.kc-calculation{margin-top:18px;background:#eaf1ef;border:1px solid #d1ddda;border-radius:12px;padding:14px;font-family:ui-monospace,SFMono-Regular,Consolas,monospace;line-height:1.7;overflow-wrap:anywhere}.kc-explanation{margin-top:18px}.kc-explanation h3{margin-top:0;color:var(--navy)}

@media(max-width:900px){.matching-board{grid-template-columns:1fr}.kc-control-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.kc-sim-grid{grid-template-columns:1fr}}
@media(max-width:620px){.matching-start-controls{align-items:stretch;flex-direction:column}.matching-start-controls select{width:100%}.matching-status-row{align-items:stretch;flex-direction:column}.matching-card{font-size:.93rem}.kc-sim-heading{flex-direction:column}.kc-control-grid{grid-template-columns:1fr 1fr}.kc-bars{height:220px;gap:8px}.kc-bar{width:64px}.app-panel{padding-top:20px}}

/* v0.4 rate equation laboratory and board overview */
.rate-lab{max-width:1120px}.rate-app-heading{display:flex;justify-content:space-between;gap:28px;align-items:flex-start;margin-bottom:24px}.rate-app-heading h2{font-family:Georgia,"Times New Roman",serif;color:var(--navy);font-size:clamp(1.8rem,3.2vw,2.7rem);line-height:1.15;margin:.15em 0 .35em}.rate-app-heading p:not(.eyebrow){margin:0;max-width:760px;color:var(--muted)}.rate-toolbar{display:grid;grid-template-columns:1fr 1.45fr 1fr auto;align-items:end}.rate-toolbar label{min-width:0}.rate-toolbar select{width:100%;min-width:0}.checkbox-control{display:flex!important;align-items:center;gap:9px;min-height:46px;padding:9px 12px;border:1px solid #c7d1ce;border-radius:10px;background:#f8faf9;color:var(--navy)!important}.checkbox-control input{width:18px;height:18px;margin:0}.muted-control{opacity:.52}.rate-question-box{box-shadow:inset 4px 0 0 var(--teal)}.rate-data-table small{font-size:.72rem;font-weight:600;color:var(--muted)}.table-scroll{overflow-x:auto}.rate-answer-form fieldset{border:1px solid var(--line);border-radius:15px;padding:20px;margin:22px 0 0;background:#fbfcfb}.rate-answer-form legend{padding:0 8px;font-family:Georgia,"Times New Roman",serif;color:var(--navy);font-size:1.35rem;font-weight:800}.rate-input-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.rate-k-grid{grid-template-columns:1fr 1fr;margin-top:14px;padding-top:14px;border-top:1px solid var(--line)}.single-unit-grid{grid-template-columns:minmax(250px,420px);margin-top:14px}.rate-input-grid label{display:grid;gap:6px;color:var(--navy);font-weight:750}.rate-input-grid input,.rate-input-grid select{width:100%;min-width:0;padding:11px 12px;border:1px solid #9eaaae;border-radius:10px;background:#fff;color:var(--ink)}.answer-correct{border-color:#26914e!important;background:#edf9f0!important;box-shadow:0 0 0 3px rgba(38,145,78,.12)}.answer-incorrect{border-color:#c34b4b!important;background:#fff2f2!important;box-shadow:0 0 0 3px rgba(195,75,75,.11)}.clue-stack{display:grid;gap:10px;margin-top:18px}.clue-card{margin:0;padding:13px 15px;border-radius:11px;border-left:4px solid var(--copper);background:#fff8ef}.rate-solution-step{padding:4px 0 18px;border-bottom:1px solid var(--line)}.rate-solution-step:last-child{border-bottom:0}.rate-solution-step h3{color:var(--navy);margin:.7em 0 .35em}.rate-solution-step ol{margin-top:.4em}.equation-result{display:inline-block;padding:10px 14px;border:1px solid #bed4ce;border-radius:10px;background:#eaf3f0;color:var(--navy);font-family:Georgia,"Times New Roman",serif;font-size:1.2rem;font-weight:800}.board-scope-note{margin:0 0 18px;padding:14px 16px;border-radius:12px}.board-scope-note.aqa-note{background:#eef3f8;border:1px solid #cbd9e7;color:#234c70}.board-scope-note.ocr-note{background:#eef7f2;border:1px solid #c8dfd1;color:#205c3b}.detective-case-file{box-shadow:inset 4px 0 0 var(--copper)}.evidence-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:18px}.evidence-card{display:grid;grid-template-columns:38px 1fr;gap:12px;align-items:start;padding:15px;border:1px solid #d4ddda;border-radius:13px;background:#fff}.evidence-card.ocr-evidence{border-color:#a9cfba;background:#f0f8f3}.evidence-number{display:grid;place-items:center;width:34px;height:34px;border-radius:10px;background:var(--navy);color:white;font-weight:850}.evidence-card.ocr-evidence .evidence-number{background:#2f744d}.evidence-card p{margin:0}.evidence-type{text-transform:uppercase;letter-spacing:.08em;font-size:.72rem;font-weight:850;color:var(--copper);margin-bottom:4px!important}.ocr-evidence .evidence-type{color:#2f744d}.board-route-card{min-height:240px}.board-route-card .tag{margin-bottom:4px}
@media(max-width:900px){.rate-toolbar{grid-template-columns:1fr 1fr}.rate-toolbar .button{width:100%}.rate-input-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.evidence-grid{grid-template-columns:1fr}}
@media(max-width:620px){.rate-app-heading{flex-direction:column}.rate-toolbar{display:flex;flex-direction:column;align-items:stretch}.rate-toolbar label,.rate-toolbar .button{width:100%}.rate-input-grid,.rate-k-grid,.single-unit-grid{grid-template-columns:1fr}.rate-answer-form fieldset{padding:16px}.evidence-card{grid-template-columns:32px 1fr}.evidence-number{width:30px;height:30px}}

/* Maxwell–Boltzmann explorer */
.boltz-app{overflow:hidden}.boltz-board-tabs{display:flex;gap:8px;margin-bottom:18px}.boltz-board-tabs button{flex:1;border:1px solid #a9b6b2;background:#fff;color:var(--navy);border-radius:10px;padding:11px 14px;font-weight:800}.boltz-board-tabs button.active{background:var(--navy);color:#fff;border-color:var(--navy)}.boltz-change-strip{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-bottom:18px}.boltz-change-strip article{display:grid;grid-template-columns:auto 1fr;column-gap:10px;align-items:center;background:#eef5f2;border:1px solid #d3dfdb;border-radius:13px;padding:13px 14px}.boltz-change-strip strong{color:var(--navy);line-height:1.15}.boltz-change-strip article>span:last-child{grid-column:2;color:var(--muted);font-size:.88rem}.change-icon{grid-row:1/3;display:grid;place-items:center;width:38px;height:38px;border-radius:11px;background:var(--teal);color:#fff;font-size:1.45rem;font-weight:900}.boltz-layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:22px;align-items:start}.boltz-visual-column{min-width:0}.boltz-graph-frame{position:relative}.boltz-graph-frame canvas{width:100%;margin:0;background:var(--paper)}.canvas-fallback{position:absolute;left:-9999px}.boltz-legend{display:flex;gap:14px;flex-wrap:wrap;margin:11px 0 15px;color:var(--muted);font-size:.84rem}.boltz-legend span{display:flex;align-items:center;gap:6px}.boltz-legend i{display:inline-block;width:25px;height:4px;border-radius:4px}.legend-current{background:var(--teal)}.legend-reference{height:0!important;border-top:3px dashed #7b8790}.legend-ea{background:var(--copper)}.legend-catalyst{background:#6f4a8e}.boltz-particles{border:1px solid var(--line);border-radius:12px;overflow:hidden;background:#eaf4f2}.boltz-particles canvas{width:100%;margin:0;border:0;border-radius:0}.boltz-controls{display:grid;gap:14px;background:#f2f6f4;border:1px solid #d5dfdc;border-radius:15px;padding:17px}.range-control{display:grid;grid-template-columns:1fr auto;gap:5px;font-weight:800;color:var(--navy)}.range-control output{color:var(--teal2);font-size:.9rem}.range-control input{grid-column:1/3;width:100%;accent-color:var(--teal)}.range-control small{grid-column:1/3;display:flex;justify-content:space-between;color:var(--muted);font-weight:500}.switch-row{display:grid;grid-template-columns:auto 1fr;gap:10px;align-items:start;padding:11px 0;border-top:1px solid #d7e0dd;color:var(--navy)}.switch-row input{margin-top:4px;accent-color:var(--teal);width:19px;height:19px}.switch-row span{display:grid}.switch-row small{color:var(--muted);font-weight:500;line-height:1.35}.boltz-reset{width:100%}.boltz-metrics{display:grid;grid-template-columns:repeat(4,1fr);gap:11px;margin-top:18px}.boltz-metrics article{display:grid;gap:4px;background:#fff8ef;border:1px solid #ead8c6;border-radius:13px;padding:14px}.boltz-metrics span{font-size:.84rem;color:var(--muted)}.boltz-metrics strong{font-size:1.32rem;color:var(--navy)}.board-ocr .aqa-only{opacity:.62}.boltz-explanation{margin-top:16px}.boltz-teacher-notes{margin-top:14px;border:1px solid var(--line);border-radius:12px;padding:12px 15px;background:#fff}.boltz-teacher-notes summary{font-weight:800;color:var(--navy);cursor:pointer}.privacy-choice{margin:24px 0}.admin-login{margin:auto}.admin-toolbar{display:flex;justify-content:space-between;gap:20px;align-items:end;margin-bottom:22px}.admin-toolbar label{display:grid;gap:5px;font-weight:800;color:var(--navy)}.admin-toolbar select{padding:9px;border:1px solid var(--line);border-radius:8px;background:#fff}.metric-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:14px;margin-bottom:22px}.metric-grid article{display:grid;background:var(--navy);color:#fff;border-radius:15px;padding:20px}.metric-grid strong{font-size:2rem}.metric-grid span{color:#c7d4d7}.dashboard-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px}.dashboard-panel{padding:22px}.dashboard-panel h2{margin-top:0;color:var(--navy)}.dashboard-panel.wide{grid-column:1/-1}.daily-bars{height:220px;display:flex;gap:5px;align-items:end;border-bottom:1px solid var(--line);padding:8px 0 28px;overflow-x:auto}.daily-bars>div{height:100%;min-width:18px;flex:1;display:flex;flex-direction:column;justify-content:end;align-items:center;position:relative}.daily-bars span{display:block;width:70%;min-height:2px;background:var(--teal);border-radius:4px 4px 0 0}.daily-bars small{position:absolute;top:100%;font-size:.64rem;transform:rotate(-55deg);transform-origin:top left;color:var(--muted);white-space:nowrap}
@media(max-width:900px){.boltz-layout{grid-template-columns:1fr}.boltz-controls{grid-template-columns:1fr 1fr}.boltz-reset{align-self:end}.boltz-metrics{grid-template-columns:repeat(2,1fr)}}
@media(max-width:660px){.boltz-change-strip{grid-template-columns:1fr}.boltz-controls{grid-template-columns:1fr}.boltz-metrics{grid-template-columns:1fr 1fr}.boltz-board-tabs{flex-direction:column}.metric-grid{grid-template-columns:1fr 1fr}.dashboard-grid{grid-template-columns:1fr}.dashboard-panel.wide{grid-column:auto}.admin-toolbar{align-items:stretch;flex-direction:column}.boltz-legend{font-size:.78rem;gap:9px}}
@media(max-width:420px){.boltz-metrics,.metric-grid{grid-template-columns:1fr}.boltz-change-strip article{padding:11px}.boltz-app{padding:16px}.boltz-controls{padding:13px}}
@media(prefers-reduced-motion:reduce){.boltz-app *{scroll-behavior:auto!important;transition:none!important}}
.board-ocr:not(.show-supplemental) .aqa-only{display:none}
[hidden]{display:none!important}

/* v0.6 visual identity refresh: Chemistry Help UK */
:root{
  --navy:#153f53;
  --navy2:#1e566f;
  --cream:#f3f5f4;
  --paper:#f8faf9;
  --teal:#087a8a;
  --teal2:#075f6c;
  --cyan:#18a9cf;
  --cyan-soft:#e4f5f9;
  --copper:#a86549;
  --copper-soft:#f5e9e2;
  --ink:#142832;
  --muted:#536771;
  --line:#ccd9dc;
  --good:#17663d;
  --bad:#963434;
  --shadow:0 18px 55px rgba(13,58,76,.12);
  --shadow-soft:0 8px 28px rgba(13,58,76,.08);
  --radius:20px;
  --max:1200px;
}
html{scroll-padding-top:92px}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:"Open Sans","Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  line-height:1.62;
  text-rendering:optimizeLegibility;
}
h1,h2,h3,h4,h5,h6,.hero h1,.page-hero h1,.section-heading h2,.split-callout h2,.prose h2,.statement-card h2,.rate-app-heading h2,.rate-answer-form legend,.hero-panel h2{
  font-family:"Open Sans","Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  letter-spacing:-.025em;
}
a{color:#066b7a}
a:hover{color:#8d4e35}
:focus-visible{outline:3px solid #f3b37c;outline-offset:3px;border-radius:7px}
.skip-link{background:#fff;color:var(--navy);border-radius:8px;box-shadow:var(--shadow)}

.staging-banner{
  display:flex;align-items:center;justify-content:center;gap:10px;
  min-height:32px;padding:5px 16px;background:#f8df9d;color:#442f08;
  font-size:.8rem;border-bottom:1px solid #d3b96e;
}
.staging-banner strong{text-transform:uppercase;letter-spacing:.08em;font-size:.72rem}

.site-header{
  background:rgba(30,86,111,.97);
  border-bottom:1px solid rgba(255,255,255,.18);
  box-shadow:0 5px 22px rgba(4,35,49,.16);
}
.header-inner{min-height:76px}
.brand,.brand:hover{color:#fff}
.brand strong{font-size:1.15rem;letter-spacing:-.02em}
.brand small{color:#d7edf2;font-size:.73rem;letter-spacing:.01em}
.brand-mark{
  position:relative;width:47px;height:47px;border-radius:50%;
  background:linear-gradient(145deg,#f7fbfc,#cfeef5);
  border:2px solid rgba(255,255,255,.7);
  box-shadow:0 6px 16px rgba(0,0,0,.18),inset 0 0 0 5px rgba(24,169,207,.12);
}
.brand-core{position:absolute;width:9px;height:9px;border-radius:50%;background:var(--cyan);box-shadow:0 0 0 4px rgba(24,169,207,.16)}
.brand-orbit{position:absolute;width:31px;height:14px;border:1.7px solid var(--navy2);border-radius:50%;transform:rotate(-28deg)}
.brand-orbit:before,.brand-orbit:after{content:"";position:absolute;width:5px;height:5px;border-radius:50%;background:var(--copper)}
.brand-orbit:before{left:0;top:3px}.brand-orbit:after{right:0;bottom:3px}
.main-nav{gap:2px}
.main-nav a{color:#f4fbfc;font-weight:650;padding:10px 11px;border-radius:10px;font-size:.91rem}
.main-nav a:hover,.main-nav a[aria-current=page]{background:rgba(255,255,255,.17);color:#fff}
.nav-toggle{color:#fff;border-color:rgba(255,255,255,.4);background:rgba(255,255,255,.1);font-weight:700}

.hero{
  min-height:630px;
  display:grid;align-items:center;
  padding:82px 0;
  background-image:
    linear-gradient(90deg,rgba(9,48,64,.52) 0%,rgba(15,69,88,.16) 44%,rgba(8,47,63,.46) 100%),
    url('../images/brand/chemistry-help-lab-home.webp');
  background-size:cover;background-position:center;
  color:var(--ink);
}
.hero:after{display:none}
.hero-grid{grid-template-columns:minmax(0,1.25fr) minmax(285px,.68fr);gap:30px;align-items:stretch}
.hero-copy{
  align-self:center;
  background:rgba(255,255,255,.92);
  border:1px solid rgba(255,255,255,.85);
  border-radius:28px;
  padding:clamp(30px,5vw,58px);
  box-shadow:0 28px 70px rgba(7,42,57,.24);
  backdrop-filter:blur(10px);
}
.hero h1{font-size:clamp(2.45rem,5vw,4.8rem);line-height:1.03;color:var(--navy);max-width:790px;margin:.16em 0 .32em;font-weight:760}
.hero .lede{color:#304b58;opacity:1;max-width:720px;font-size:clamp(1.04rem,1.8vw,1.28rem)}
.hero .eyebrow{color:var(--copper)}
.hero .button.secondary{background:#fff;border-color:#8aa8b3;color:var(--navy)}
.hero .button.secondary:hover{background:#eef7f9;color:var(--navy)}
.hero-panel{
  align-self:center;
  background:rgba(18,71,91,.93);
  border:1px solid rgba(255,255,255,.34);
  padding:27px;
  border-radius:24px;
  box-shadow:0 24px 60px rgba(7,42,57,.27);
  color:#fff;
}
.hero-panel h2{font-size:1.75rem;line-height:1.18;margin:.55em 0 .7em;color:#fff}
.hero-panel .label{background:#dff5fa;color:#154c60}
.hero-links{display:grid;gap:9px}
.hero-links a{display:grid;gap:2px;padding:12px 13px;border-radius:12px;background:rgba(255,255,255,.09);border:1px solid rgba(255,255,255,.15);text-decoration:none;color:#fff}
.hero-links a:hover{background:rgba(255,255,255,.17);color:#fff}
.hero-links span{font-weight:750}.hero-links small{color:#cce6ec;font-weight:500}

.page-hero{
  position:relative;overflow:hidden;
  min-height:360px;display:grid;align-items:center;
  padding:56px 0;
  border-bottom:0;
  background-size:cover;background-position:center;
}
body.visual-learning .page-hero{
  background-image:linear-gradient(90deg,rgba(13,62,80,.28),rgba(255,255,255,.05),rgba(13,62,80,.28)),url('../images/brand/chemistry-help-lab-learning.webp');
}
body.visual-tools .page-hero{
  background-image:linear-gradient(90deg,rgba(13,62,80,.26),rgba(255,255,255,.03),rgba(13,62,80,.25)),url('../images/brand/chemistry-help-lab-tools.webp');
}
.page-hero .shell{
  width:min(calc(100% - 36px),850px);
  background:rgba(255,255,255,.91);
  border:1px solid rgba(255,255,255,.9);
  border-radius:24px;
  padding:clamp(25px,4vw,42px);
  text-align:center;
  box-shadow:0 22px 58px rgba(8,47,63,.22);
  backdrop-filter:blur(9px);
}
.page-hero h1{font-size:clamp(2.1rem,4.5vw,4rem);line-height:1.08;color:var(--navy);font-weight:760;margin:.15em auto .28em;max-width:840px}
.page-hero .lede{margin:0 auto;color:#3d5662;opacity:1;font-size:clamp(1rem,1.8vw,1.22rem)}
.page-hero .eyebrow{color:var(--copper)}
.page-hero .button{margin-top:18px}
.hub-note{display:inline-block;margin:18px auto 0;padding:9px 13px;border-radius:12px;background:rgba(230,246,249,.92);color:#295869;font-size:.9rem;max-width:720px}

.section{padding:72px 0}
.section-tint{
  background-color:#edf5f6;
  background-image:radial-gradient(circle at 12% 18%,rgba(24,169,207,.10) 0 2px,transparent 3px),radial-gradient(circle at 88% 76%,rgba(8,122,138,.08) 0 2px,transparent 3px);
  background-size:72px 72px,92px 92px;
}
.section-heading{margin-bottom:31px}
.section-heading h2,.split-callout h2,.prose h2{color:var(--navy);font-weight:750;line-height:1.14}
.section-heading>p{color:var(--muted);font-size:1.01rem}
.eyebrow{color:var(--copper);letter-spacing:.13em;font-weight:800}

.card-grid{gap:20px}
.card{
  position:relative;overflow:hidden;
  background:rgba(255,255,255,.97);
  border:1px solid #cfdbde;
  border-radius:20px;
  padding:25px;
  box-shadow:var(--shadow-soft);
}
.card:before{content:"";position:absolute;inset:0 0 auto 0;height:5px;background:linear-gradient(90deg,var(--teal),var(--cyan))}
.card:hover{transform:translateY(-4px);border-color:#9dbdc6;box-shadow:var(--shadow)}
.card h2,.card h3{font-weight:740;color:var(--navy)}
.card p{color:#566a73}
.card-link{color:#087181}
.board-card.aqa-card:before{background:linear-gradient(90deg,#9b5b42,#d49a76)}
.board-card.ocr-card:before{background:linear-gradient(90deg,#0a7785,#21afd0)}
.board-card.aqa-card .tag{background:#f4e6df;color:#77412d}
.board-card.ocr-card .tag{background:#e2f5f8;color:#075a69}
.tag,.hero-panel .label{border-radius:999px;padding:5px 10px;font-size:.73rem}
.tool-icon{width:48px;height:48px;border-radius:14px;background:linear-gradient(145deg,var(--navy2),var(--teal));color:#fff;box-shadow:0 7px 16px rgba(8,91,107,.18)}
.board-route-card{min-height:230px}

.button{min-height:48px;border-radius:12px;padding:11px 19px;font-weight:750;box-shadow:none}
.button.primary{background:linear-gradient(135deg,var(--teal),#0b91a3);color:#fff;border-color:#08727f}
.button.primary:hover{background:linear-gradient(135deg,#056b78,#087c8c);color:#fff}
.button.secondary{background:#fff;border-color:#91abb4;color:var(--navy)}
.button.secondary:hover{background:#eaf5f7;border-color:#648f9d;color:var(--navy)}
.text-button{color:#086f7d}

.interactive{
  position:relative;
  background:rgba(255,255,255,.98);
  border:1px solid #c9d8dc;
  border-radius:22px;
  box-shadow:0 20px 58px rgba(13,58,76,.12);
}
.interactive:before{content:"";position:absolute;inset:0 0 auto 0;height:6px;background:linear-gradient(90deg,var(--navy2),var(--cyan),var(--copper));border-radius:22px 22px 0 0}
.question-box,.rate-question-box{background:#edf6f7;border:1px solid #d3e4e7}
.statement-card{background:linear-gradient(135deg,var(--navy),var(--navy2));box-shadow:0 14px 30px rgba(13,58,76,.17)}
.statement-card h2{font-weight:700}
.generator-toolbar{border-bottom-color:#d3dfe2}
.generator-toolbar select,.rate-input-grid input,.rate-input-grid select,.answer-form input,.multi-answer input,.contact-form input,.contact-form textarea,.admin-toolbar select{
  border:1px solid #91aab3;
  background:#fff;
  color:var(--ink);
  min-height:46px;
}
.generator-toolbar select:focus,.rate-input-grid input:focus,.rate-input-grid select:focus,.answer-form input:focus,.multi-answer input:focus,.contact-form input:focus,.contact-form textarea:focus{border-color:var(--cyan);box-shadow:0 0 0 3px rgba(24,169,207,.16);outline:0}
.data-table{border-radius:12px;overflow:hidden;box-shadow:0 4px 15px rgba(13,58,76,.05)}
.data-table th{background:#dceef2;color:#183f50;border-color:#b9cdd2}
.data-table td{border-color:#d3e0e3}
.option-stack button,.choice-row button,.matching-card{min-height:48px}
.option-stack button:hover,.choice-row button:hover{background:#e6f5f7;border-color:#4c9caf}
.progress-track span{background:linear-gradient(90deg,var(--teal),var(--cyan))}
.notice{background:#fff5ed;border-left-color:var(--copper);box-shadow:0 5px 17px rgba(138,82,54,.06)}
.solution-panel{background:#edf5f6;border-color:#c6dadd}
.feedback-panel.good{background:#e9f6ee}.feedback-panel.bad{background:#fff0ef}

.legacy-intro-grid{align-items:center}
.legacy-figure{border-radius:22px;overflow:hidden;box-shadow:var(--shadow);background:#fff;border:1px solid #c8d8dc}
.legacy-figure img{display:block;width:100%;height:auto}
.legacy-figure figcaption{padding:11px 15px;background:#f4f8f8;color:#49616b;font-size:.9rem}
.featured-game-card{border-radius:24px;background:linear-gradient(135deg,#eaf7f9,#fff);border-color:#bcd7de;box-shadow:var(--shadow-soft)}
.featured-game-card:hover{box-shadow:var(--shadow)}
.retrieval-callout{position:relative}
.retrieval-callout:before{content:"";position:absolute;left:calc(50% - 50vw);right:calc(50% - 50vw);top:0;bottom:0;background:linear-gradient(90deg,rgba(24,169,207,.05),transparent 40%,rgba(168,101,73,.05));z-index:-1}

.app-tabs{border-radius:14px;background:#e8f2f4;border-color:#cbdcdf}
.app-tab{color:#345462;font-weight:750}.app-tab.active{background:var(--navy2);color:#fff}
.matching-start-mark{background:linear-gradient(145deg,var(--navy2),var(--cyan));color:#fff}
.matching-message.good{background:#e8f5ed;color:#17633d}
.colour-orbit{filter:saturate(.92)}
.kc-visual-panel,.kc-data-panel,.boltz-controls{background:#eef5f6;border-color:#cbdcdf}
.kc-bar.n2{background:#3b87b8}.kc-bar.h2{background:#4f9a72}.kc-bar.nh3{background:#cc7d4f}
.boltz-change-strip article{background:#eaf5f6;border-color:#ccdee2}
.change-icon{background:linear-gradient(145deg,var(--teal),var(--cyan))}
.boltz-metrics article{background:#fff4eb;border-color:#e5cdbd}
.metric-grid article{background:linear-gradient(145deg,var(--navy),var(--navy2))}

.site-footer{
  position:relative;overflow:hidden;
  background:linear-gradient(135deg,#123b4e,#1e566f 65%,#176173);
  color:#e7f1f3;
  padding:58px 0 25px;
  margin-top:0;
}
.site-footer:after{content:"";position:absolute;width:420px;height:420px;border:1px solid rgba(255,255,255,.09);border-radius:50%;right:-160px;bottom:-300px;box-shadow:0 0 0 60px rgba(255,255,255,.025),0 0 0 120px rgba(255,255,255,.018)}
.footer-grid{position:relative;z-index:1;grid-template-columns:1.7fr 1fr 1fr;gap:42px}
.footer-grid strong{color:#fff;font-size:1rem}
.footer-brand-block>strong{font-size:1.25rem}
.footer-grid p{color:#c8dade}
.footer-grid nav{gap:9px}.footer-grid a{color:#e9f5f7;text-decoration-color:rgba(255,255,255,.35)}
.footer-grid a:hover{color:#fff;text-decoration-color:#fff}
.footer-small{position:relative;z-index:1;display:flex;justify-content:space-between;gap:20px;color:#b8d0d5}

@media(max-width:1000px){
  .main-nav a{padding:9px 8px;font-size:.86rem}
  .hero{min-height:590px}
  .hero-grid{grid-template-columns:1fr .72fr}
}
@media(max-width:900px){
  .main-nav{top:68px;background:#fff;border-color:#bfd0d4;box-shadow:var(--shadow)}
  .main-nav a{color:var(--navy);font-size:.96rem;padding:11px 13px}
  .main-nav a:hover,.main-nav a[aria-current=page]{background:#e6f3f6;color:var(--navy)}
  .hero{min-height:auto;padding:65px 0;background-position:center}
  .hero-grid{grid-template-columns:1fr;max-width:760px}
  .hero-panel{max-width:610px}
  .page-hero{min-height:330px}
  .footer-grid{grid-template-columns:1.5fr 1fr 1fr}
}
@media(max-width:700px){
  .brand strong{font-size:1.02rem}
  .brand-mark{width:42px;height:42px}.brand-orbit{width:27px}
  .hero{padding:48px 0;background-position:center}
  .hero-copy{padding:27px 23px;border-radius:22px}
  .hero-panel{padding:22px;border-radius:20px}
  .page-hero{min-height:300px;padding:34px 0;background-position:center}
  .page-hero .shell{padding:24px 20px;border-radius:20px;width:min(calc(100% - 24px),850px)}
  .section{padding:52px 0}
  .footer-grid{grid-template-columns:1fr 1fr}.footer-brand-block{grid-column:1/-1}
  .footer-small{flex-direction:column}
}
@media(max-width:480px){
  .staging-banner{font-size:.72rem;flex-wrap:wrap;gap:5px}
  .header-inner{min-height:68px}
  .brand small{display:none}
  .nav-toggle{padding:8px 9px}
  .hero h1{font-size:clamp(2.15rem,12vw,3.2rem)}
  .hero .lede{font-size:1rem}
  .hero-copy,.hero-panel{backdrop-filter:none}
  .page-hero .shell{backdrop-filter:none}
  .card{padding:21px}
  .footer-grid{grid-template-columns:1fr}.footer-brand-block{grid-column:auto}
}
@media(prefers-reduced-motion:reduce){
  *{scroll-behavior:auto!important;transition:none!important;animation:none!important}
}

/* v0.7 back titration exam generator */
.bt-main-tabs{margin-bottom:0}
.bt-panel-heading{display:flex;align-items:end;justify-content:space-between;gap:28px;padding:25px 2px 8px}
.bt-panel-heading h2{margin:.12em 0;color:var(--navy);font-size:clamp(1.55rem,2.7vw,2.25rem);line-height:1.15}
.bt-panel-heading>p{max-width:430px;margin:0;color:var(--muted)}
.bt-exam-toolbar,.bt-set-toolbar{display:grid;grid-template-columns:repeat(4,minmax(145px,1fr)) auto;align-items:end}
.bt-set-toolbar{grid-template-columns:repeat(5,minmax(125px,1fr));}
.bt-exam-toolbar label,.bt-set-toolbar label{min-width:0}
.bt-exam-toolbar select,.bt-set-toolbar select{min-width:0;width:100%}
.scope-note{margin:-10px 0 20px;padding:11px 14px;border-radius:11px;background:#edf5f6;border:1px solid #cbdde1;color:#365561;font-size:.9rem}
.scope-note.extension{background:#fff5e9;border-color:#e6c9ad;color:#714a2f}
.bt-question-meta{display:flex;gap:8px;flex-wrap:wrap;margin:6px 0 15px}
.bt-question-meta span{display:inline-flex;align-items:center;border-radius:999px;background:#e6f3f5;border:1px solid #c5dfe4;color:var(--teal2);padding:5px 10px;font-size:.78rem;font-weight:800}
.bt-exam-paper{margin:18px 0 22px;background:#fff;border:1px solid #aeb8bc;box-shadow:0 10px 30px rgba(15,54,70,.08);color:#101820}
.bt-paper-header{display:grid;grid-template-columns:auto 1fr auto;gap:18px;align-items:center;padding:14px 18px;border-bottom:2px solid #263b45;background:#f7f8f8}
.bt-paper-header p{margin:0;color:#55666e;font-size:.78rem;text-transform:uppercase;letter-spacing:.07em;font-weight:800}
.bt-paper-header>div>strong{display:block;color:#183f52;font-size:.98rem}
.bt-paper-number{display:grid;grid-template-columns:auto auto;align-items:stretch;border:1px solid #263b45;background:#fff}
.bt-paper-number span{display:grid;place-items:center;padding:5px 8px;border-right:1px solid #263b45;font-size:.7rem;text-transform:uppercase;letter-spacing:.05em;font-weight:800}
.bt-paper-number strong{display:grid;place-items:center;min-width:42px;padding:5px 8px;font-size:1.05rem}
.bt-paper-marks{white-space:nowrap;font-weight:800;color:#183f52}
.bt-paper-body{padding:clamp(20px,4vw,38px);font-size:1rem;line-height:1.58}
.bt-paper-body h3{margin:0 0 22px;color:#183f52;font-size:clamp(1.25rem,2.3vw,1.75rem)}
.bt-paper-body p{margin:.8em 0}
.bt-paper-equation{margin:20px auto;padding:10px 16px;text-align:center;font-size:1.12rem;font-weight:650;letter-spacing:.01em}
.bt-paper-equation-pair,.bt-paper-equations{display:grid;gap:10px;margin:20px 0}
.bt-paper-equation-pair span,.bt-paper-equations span{display:block;padding:10px 13px;border-left:3px solid #427b8d;background:#f4f7f8;font-size:.98rem;overflow-wrap:anywhere}
.bt-paper-method{margin:16px 0;padding-left:1.4rem}
.bt-paper-method li{margin:.55em 0}
.bt-data-line{font-weight:800}
.bt-paper-task{display:grid;grid-template-columns:auto minmax(0,1fr) auto;gap:14px;align-items:start;margin-top:26px;padding-top:20px;border-top:1px solid #9da9ad}
.bt-paper-task p{margin:0;font-weight:750}
.bt-paper-task>strong{white-space:nowrap;align-self:end}
.bt-part-label{font-weight:800}
.bt-origin-note{margin-top:28px!important;padding-top:12px;border-top:1px dashed #c8ced1;color:#6e7b81;font-size:.76rem}
.bt-table-wrap{max-width:100%;overflow-x:auto;margin:20px 0;-webkit-overflow-scrolling:touch}
.bt-results-table,.bt-mark-table{width:100%;border-collapse:collapse;background:#fff;min-width:590px}
.bt-results-table caption{text-align:center;font-weight:800;padding:6px;color:#183f52}
.bt-results-table th,.bt-results-table td,.bt-mark-table th,.bt-mark-table td{border:1px solid #53646c;padding:9px 10px;text-align:center}
.bt-results-table thead th,.bt-mark-table thead th{background:#edf2f3;color:#183f52}
.bt-results-table tbody th{text-align:left;background:#f7f8f8;white-space:nowrap}
.bt-exam-answer-form{margin:20px 0}
.bt-exam-answer-form fieldset{margin:0;padding:20px;border:1px solid var(--line);border-radius:14px;background:#f7faf9}
.bt-exam-answer-form legend{padding:0 7px;color:var(--navy);font-weight:850;font-size:1.05rem}
.bt-answer-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:15px;margin-bottom:17px}
.bt-answer-grid label{display:grid;gap:7px;color:var(--navy);font-weight:750}
.bt-input-with-unit{display:grid;grid-template-columns:minmax(0,1fr) auto;align-items:stretch}
.bt-input-with-unit input{min-width:0;width:100%;padding:11px 12px;border:1px solid #91a2a8;border-radius:10px 0 0 10px;background:#fff}
.bt-input-with-unit b{display:grid;place-items:center;padding:0 11px;border:1px solid #91a2a8;border-left:0;border-radius:0 10px 10px 0;background:#eaf2f3;color:#244956;font-size:.82rem;white-space:nowrap}
.bt-input-with-unit input.input-correct{border-color:#2f8a58;background:#effaf3;box-shadow:inset 0 0 0 1px #2f8a58}
.bt-input-with-unit input.input-incorrect{border-color:#bd5555;background:#fff2f2;box-shadow:inset 0 0 0 1px #bd5555}
.bt-mark-scheme{background:#fff!important}
.bt-mark-summary{padding:12px 14px;background:#edf6f4;border-left:4px solid var(--teal);border-radius:0 9px 9px 0}
.bt-mark-table th:first-child,.bt-mark-table td:first-child{text-align:left}
.bt-mark-table th:last-child,.bt-mark-table td:last-child{width:70px;text-align:center;font-weight:800}
.bt-mark-total th{background:#dfecee;color:#173f50}
.bt-set-mark-heading{display:flex;justify-content:space-between;gap:20px;align-items:center;border-bottom:2px solid #183f52;margin:12px 0 20px}
.bt-set-mark-heading h2{color:#183f52}
.practice-set .bt-exam-paper{break-inside:avoid}
.practice-set .answer-key section{break-inside:auto}

@media(max-width:980px){
  .bt-exam-toolbar{grid-template-columns:repeat(2,minmax(180px,1fr))}
  .bt-set-toolbar{grid-template-columns:repeat(3,minmax(150px,1fr))}
  .bt-exam-toolbar .button,.bt-set-toolbar .toolbar-actions{width:100%}
}
@media(max-width:700px){
  .bt-panel-heading{display:block}.bt-panel-heading>p{max-width:none;margin-top:8px}
  .bt-exam-toolbar,.bt-set-toolbar{grid-template-columns:1fr 1fr}
  .bt-paper-header{grid-template-columns:1fr auto}.bt-paper-number{display:none}.bt-paper-header>div:nth-child(2){grid-column:1}.bt-paper-marks{grid-column:2;grid-row:1}
  .bt-paper-body{padding:20px 17px}
  .bt-paper-task{grid-template-columns:auto 1fr}.bt-paper-task>strong{grid-column:2;justify-self:end}
}
@media(max-width:480px){
  .bt-exam-toolbar,.bt-set-toolbar{grid-template-columns:1fr}
  .bt-answer-grid{grid-template-columns:1fr}
  .bt-input-with-unit{grid-template-columns:1fr}.bt-input-with-unit input{border-radius:10px 10px 0 0}.bt-input-with-unit b{border-left:1px solid #91a2a8;border-top:0;border-radius:0 0 10px 10px;padding:7px}
  .bt-paper-header{padding:12px}.bt-paper-header>div>strong{font-size:.88rem}.bt-paper-marks{font-size:.82rem}
  .bt-paper-equation{font-size:1rem;padding-inline:3px}
}

@media print{
  #bt-method-panel,#bt-exam-panel{display:none!important}
  #bt-set-panel{display:block!important}
  .bt-panel-heading{display:none!important}
  .practice-set .bt-exam-paper{box-shadow:none;border:1px solid #222;margin:0 0 14px}
  .bt-paper-header{background:#fff;border-bottom:1.5px solid #000;padding:8px 10px}
  .bt-paper-body{padding:14px 16px;font-size:9.8pt}
  .bt-paper-body h3{font-size:12pt;margin-bottom:10px}
  .bt-paper-body p{margin:.5em 0}.bt-paper-equation-pair,.bt-paper-equations{margin:10px 0;gap:5px}.bt-paper-equation-pair span,.bt-paper-equations span{padding:5px 8px;background:#fff;border-left:2px solid #000}
  .bt-table-wrap{overflow:visible}.bt-results-table,.bt-mark-table{min-width:0;font-size:8.8pt}.bt-results-table th,.bt-results-table td,.bt-mark-table th,.bt-mark-table td{padding:5px 6px;border-color:#000}
  .bt-origin-note{display:none}.bt-paper-task{margin-top:12px;padding-top:10px}
  .answer-key{display:block!important;break-before:page}.answer-key summary{display:none!important}.answer-key section{break-inside:avoid}
  .bt-mark-summary{background:#fff;border:1px solid #000}.bt-set-mark-heading{border-color:#000}
}
@media print{
  .answer-key{display:block!important}
  .answer-key>summary{display:none!important}
  .answer-key>:not(summary){display:block!important}
}