:root{--paper:#f7f3ea;--sheet:#fffdf8;--ink:#22251f;--muted:#62645d;--line:#d8d2c5;--yellow:#f4cf4f;--blue:#234f9d;--green:#315c43;--serif:Georgia,"Times New Roman",serif;--sans:Arial,Helvetica,sans-serif}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:100px}body{margin:0;background:var(--sheet);color:var(--ink);font-family:var(--sans);font-size:16px;line-height:1.6}a{color:inherit;text-decoration:none}button{font:inherit;color:inherit;cursor:pointer}img{display:block;max-width:100%}button,a{-webkit-tap-highlight-color:transparent}button:disabled{cursor:default;opacity:.45}[hidden]{display:none!important}button:focus-visible,a:focus-visible,summary:focus-visible,[tabindex]:focus-visible{outline:3px solid var(--blue);outline-offset:5px}h1,h2,h3,p{margin-top:0}h1,h2,h3{font-weight:400}h1,h2{font-family:var(--serif)}h2{font-size:clamp(34px,4.2vw,54px);line-height:1.12;letter-spacing:-.045em;margin-bottom:22px}h2 em{font-weight:400}p{margin-bottom:18px}.wrap{width:min(1180px,calc(100% - 80px));margin-inline:auto}.skip-link{position:fixed;left:20px;top:-100px;z-index:200;background:var(--ink);color:white;padding:12px 20px}.skip-link:focus{top:12px}.preview-label{min-height:31px;background:#eae4d7;color:#4f514b;padding:6px 40px;font-size:10px;font-weight:700;letter-spacing:.13em;display:flex;align-items:center;gap:13px}.preview-local{margin-left:auto;font-size:10px;font-weight:400;letter-spacing:.02em}.site-header{background:rgba(255,253,248,.97);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:30}.nav-row{min-height:85px;display:flex;align-items:center;justify-content:space-between;gap:30px}.brand{flex-shrink:0}.brand img{width:184px;height:54px;object-fit:contain}nav{display:flex;align-items:center;gap:30px;font-size:13px}nav>a:not(.nav-cta):hover{text-decoration:underline;text-underline-offset:6px}.nav-cta{border:1px solid var(--ink);padding:10px 17px;border-radius:3px;display:flex;gap:20px;align-items:center;font-weight:700}.nav-cta:hover{background:var(--yellow)}.menu-toggle{display:none;min-height:44px;border:1px solid var(--line);padding:8px 12px;background:none;align-items:center;gap:14px}
.hero{background-color:var(--paper);background-image:radial-gradient(#c4beaf55 .6px,transparent .6px);background-size:7px 7px;overflow:hidden}.hero-grid{padding:79px 0 70px;display:grid;grid-template-columns:1.04fr 1fr;gap:85px;align-items:center}.eyebrow{font-size:10px;font-weight:700;letter-spacing:.16em;line-height:1.6;margin-bottom:23px;color:var(--blue)}.tiny-star{font-size:21px;vertical-align:middle;margin-right:8px}h1{font-size:clamp(64px,6.6vw,91px);line-height:1.04;letter-spacing:-.055em;margin-bottom:29px}h1 em{font-weight:400;font-style:italic;background:linear-gradient(transparent 69%,var(--yellow) 69%,var(--yellow) 92%,transparent 92%)}.intro{max-width:420px;font-size:18px;line-height:1.6;margin-bottom:12px}.hero-description{max-width:420px;font-size:15px;color:var(--muted);line-height:1.8}.hero-actions{margin-top:28px;display:flex;gap:25px;align-items:center;flex-wrap:wrap}.button{min-height:48px;display:inline-flex;align-items:center;justify-content:center;gap:23px;padding:13px 20px;font-size:12px;font-weight:700;border:1px solid transparent;border-radius:3px;line-height:1.5}.button-dark{background:var(--ink);color:var(--sheet);border-color:var(--ink)}.button-dark:hover{background:#3b4136}.text-link{font-size:12px;border-bottom:1px solid var(--ink);padding-block:8px;display:inline-flex;gap:15px}.margin-note{color:var(--blue);font-family:var(--serif);font-size:16px;font-style:italic;margin:21px 0 0;display:flex;align-items:center;gap:5px}.margin-note svg{width:53px;height:32px;fill:none;stroke:currentColor;stroke-width:1.6;stroke-linecap:round}
.hero-art{position:relative;padding:20px 3px 17px}.question-paper{position:relative;background:#fffefa;border:1px solid #d9d3c6;box-shadow:7px 9px 0 #e9e3d6,0 22px 40px #4b443514;padding:30px 31px 22px;transform:rotate(2deg)}.tape{position:absolute;top:-15px;left:38%;width:108px;height:29px;transform:rotate(-5deg);background:#ddc98bb3;border-inline:2px dashed #bfa76233}.paper-meta{display:flex;justify-content:space-between;gap:20px;font-size:9px;letter-spacing:.12em;border-bottom:1px solid var(--line);padding-bottom:14px;color:var(--muted)}.paper-kicker{font-size:12px;color:var(--muted);margin-top:25px;margin-bottom:12px}.question-paper h2{font-size:32px;line-height:1.2;letter-spacing:-.035em;margin-bottom:22px}mark{background:linear-gradient(transparent 55%,#f4cf4f99 55%,#f4cf4f99 95%,transparent 95%);color:inherit}.ruled-answer{font-size:13px;font-family:var(--serif);font-style:italic;color:var(--muted);min-height:44px;background:repeating-linear-gradient(transparent 0,transparent 27px,#d9d3c5 28px);padding-top:4px}.paper-bridge{display:flex;align-items:center;gap:13px;color:var(--blue);font-family:var(--serif);font-size:14px;font-style:italic;margin-top:12px}.paper-bridge>span:first-child{font-size:33px;line-height:1}.sticky-note{background:#f5df83;border:1px solid #e5cc6e;box-shadow:3px 6px 0 #ded9cd55;padding:18px 24px 15px;transform:rotate(-4deg);margin:18px 14px 23px 30px}.note-eyebrow{font-size:8px;letter-spacing:.15em;font-weight:700;margin-bottom:13px}.memory-title{font-family:var(--serif);font-size:41px;line-height:1.05;letter-spacing:-.025em;margin-bottom:12px}.memory-title>span{font-style:italic}.memory-key{display:flex;justify-content:flex-start;gap:30px;font-size:12px;border-top:1px solid #b7a35a;padding-top:10px}.memory-key b{text-decoration:underline;text-underline-offset:4px}.note-foot{font-family:var(--serif);font-size:13px;font-style:italic;margin:9px 0 0}.paper-bottom{display:flex;align-items:center;justify-content:space-between;gap:8px;color:var(--muted);font-size:9px}.paper-bottom svg{width:45px;height:25px;fill:none;stroke:var(--blue);stroke-width:1.7;stroke-linecap:round}.art-caption{font-family:var(--serif);font-style:italic;font-size:13px;color:var(--muted);display:block;text-align:center;margin:25px 0 -15px}.hero-foot{padding:20px 0;border-top:1px solid var(--line);display:flex;align-items:center;gap:25px;color:var(--muted);font-size:11px}.hero-foot>span:first-child{font-size:9px;letter-spacing:.14em;font-weight:700;color:var(--ink)}.foot-end{margin-left:auto;font-family:var(--serif);font-style:italic;font-size:13px}
.section-space{padding:87px 0}.section-heading{display:flex;align-items:flex-end;justify-content:space-between;gap:55px;margin-bottom:42px}.section-heading h2{margin-bottom:0}.section-heading>p{max-width:330px;color:var(--muted);font-size:14px;line-height:1.85;margin-bottom:2px}.section-heading .eyebrow{margin-bottom:17px}.method-list{padding:0;list-style:none;display:grid;grid-template-columns:repeat(4,1fr);margin:0;border-block:1px solid var(--line)}.method-list li{position:relative;padding:30px 24px 30px 0}.method-list li+li{padding-left:24px;border-left:1px solid var(--line)}.step-number{font-family:var(--serif);font-style:italic;font-size:19px;color:var(--blue);display:block;margin-bottom:19px}.method-list h3{font-family:var(--serif);font-size:24px;letter-spacing:-.03em;margin-bottom:10px}.method-list p{color:var(--muted);font-size:13px;line-height:1.75;max-width:210px;margin-bottom:0}.step-arrow{position:absolute;right:22px;top:32px;font-family:var(--serif);font-size:21px;color:var(--muted)}
.demo-section{background:var(--paper);border-block:1px solid var(--line)}.lesson{background:var(--sheet);border:1px solid #c8c1b3;box-shadow:5px 6px 0 #e8e1d4}.lesson-top{display:flex;justify-content:space-between;gap:20px;padding:16px 28px;border-bottom:1px solid var(--line);font-size:9px;font-weight:700;letter-spacing:.13em;color:var(--muted)}.lesson-tabs{display:grid;grid-template-columns:repeat(4,1fr);border-bottom:1px solid var(--line)}.lesson-tabs button{padding:17px 20px;border:0;border-bottom:3px solid transparent;background:transparent;font-size:13px;text-align:left;display:flex;align-items:center;justify-content:center;gap:15px;min-height:56px}.lesson-tabs button+button{border-left:1px solid var(--line)}.lesson-tabs button span{font-family:var(--serif);font-style:italic;color:var(--muted);font-size:15px}.lesson-tabs button[aria-selected=true]{background:#f7e8a5;border-bottom-color:var(--ink);font-weight:700}.lesson-tabs button:hover{background:#f5efdb}.lesson-body{padding:39px 44px 30px}.lesson-panel{display:grid;grid-template-columns:1.1fr 1fr;gap:65px;align-items:center;min-height:350px}.lesson-copy h3{font-family:var(--serif);font-size:35px;line-height:1.19;letter-spacing:-.035em;margin-bottom:21px}.lesson-copy>p:not(.eyebrow){font-size:14px;color:var(--muted);line-height:1.85;max-width:440px}.lesson-copy .eyebrow{font-size:9px;margin-bottom:16px}.pencil-note{border-left:2px solid var(--blue);font-family:var(--serif);font-style:italic;font-size:15px;color:var(--blue);padding-left:16px;margin-top:23px;line-height:1.7}.diagram-card{border:1px solid var(--line);padding:22px;background-color:#f9f7ef;background-image:linear-gradient(#d5d3c133 1px,transparent 1px),linear-gradient(90deg,#d5d3c133 1px,transparent 1px);background-size:20px 20px;min-width:0}.diagram-label{display:flex;justify-content:space-between;font-size:12px;color:var(--muted)}.diagram-label>span:last-child{color:var(--blue);font-size:19px}.diagram-card>p{text-align:center;font-family:var(--serif);font-size:16px;margin:18px 0 5px;line-height:1.65}.diagram-card>p>span{font-family:var(--sans);font-size:11px;color:var(--muted)}.state-controls{display:flex;gap:5px;justify-content:center;flex-wrap:wrap}.state-controls button{font-size:11px;min-height:38px;flex:1;padding:8px 7px;border:1px solid var(--line);background:var(--sheet)}.state-controls button[aria-pressed=true]{background:var(--ink);border-color:var(--ink);color:var(--sheet)}#state-explanation{font-family:var(--sans);font-size:12px}#state-explanation strong{font-weight:700}.diagram-caveat{display:block;text-align:center;margin-top:13px;font-size:9px;color:var(--muted)}.memory-demo{position:relative;background:#f5df83;border:1px solid #ddc363;padding:29px 32px;text-align:center;transform:rotate(-1deg);box-shadow:4px 5px 0 #ded7c8}.memory-arrow{fill:none;stroke:var(--blue);stroke-width:2;stroke-linecap:round;width:150px;height:40px;margin-top:12px}.memory-rule{font-family:var(--serif);font-size:23px;line-height:1.3;margin:0}.lesson-bottom{display:flex;justify-content:space-between;align-items:center;gap:20px;border-top:1px solid var(--line);padding:20px 28px;min-height:90px}.text-button{border:0;background:none;padding:10px 0;min-height:44px;font-size:12px;text-decoration:underline;text-underline-offset:5px;text-align:left;display:inline-flex;gap:12px;align-items:center}.lesson-hint{font-family:var(--serif);font-style:italic;font-size:14px;color:var(--muted);text-align:center}.recall-card{min-width:0}.answers{display:grid;gap:10px}.answers button{display:flex;align-items:flex-start;gap:13px;text-align:left;background:#fffefa;border:1px solid var(--line);padding:13px;font-size:12px;line-height:1.7;width:100%}.answers button:hover{border-color:var(--blue)}.answers button>span{font-family:var(--serif);font-style:italic;color:var(--blue);font-size:17px;line-height:1.3}.answers button[aria-pressed=true]{border-color:var(--blue);box-shadow:inset 3px 0 var(--blue)}.answers button.correct{background:#ebf2e7;border-color:var(--green);box-shadow:inset 3px 0 var(--green)}.answers button.incorrect{background:#fbf0dc;border-color:#876029;box-shadow:inset 3px 0 #876029}.answer-feedback{font-size:12px;margin:15px 0 0;line-height:1.7;color:var(--blue)}.answer-feedback:empty{display:none}.answer-feedback.correct{color:var(--green)}.model-answer{background:#f5efda;border-left:3px solid var(--yellow);padding:15px 18px;margin-top:10px;font-size:12px}.model-answer strong{font-size:10px;text-transform:uppercase;letter-spacing:.1em}.model-answer p{margin:8px 0}.model-answer small{font-size:10px;color:var(--muted)}.demo-caption{font-family:var(--serif);font-style:italic;font-size:15px;color:var(--muted);margin:22px 0 0;text-align:center}.demo-caption span{color:var(--blue);font-size:25px;vertical-align:middle;margin-right:8px}.noscript-note{padding:20px 28px;color:var(--blue);font-size:13px}
.inside-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:55px}.inside-grid article{border-top:1px solid var(--line);padding-top:25px}.sketch-icon{font-size:33px;color:var(--blue);display:block;line-height:1;margin-bottom:22px;font-family:var(--serif)}.inside-grid h3{font-family:var(--serif);font-size:27px;letter-spacing:-.03em;margin-bottom:12px}.inside-grid p{font-size:13px;color:var(--muted);line-height:1.85;max-width:310px;margin:0}.availability-note{background:#f0eee5;border:1px solid var(--line);display:flex;gap:13px;padding:19px 23px;margin-top:43px;align-items:flex-start}.availability-dot{width:7px;height:7px;background:#8d6b18;border-radius:50%;flex-shrink:0;margin-top:7px}.availability-note p{margin:0;font-size:12px;color:var(--muted);line-height:1.8}.availability-note strong{color:var(--ink);font-weight:700}
.faq-section{border-top:1px solid var(--line)}.faq-grid{display:grid;grid-template-columns:.85fr 1.15fr;gap:95px}.faq-note{font-family:var(--serif);font-size:17px;font-style:italic;line-height:1.7;color:var(--blue);margin-top:28px}.faq-list{border-top:1px solid var(--line)}details{border-bottom:1px solid var(--line)}summary{list-style:none;cursor:pointer;display:flex;gap:22px;justify-content:space-between;align-items:center;padding:24px 0;font-size:14px;font-weight:700;min-height:64px}summary::-webkit-details-marker{display:none}summary span{font-size:22px;font-weight:400;color:var(--blue);transition:transform .2s}details[open] summary span{transform:rotate(45deg)}details>p{font-size:13px;line-height:1.85;color:var(--muted);padding-right:30px;margin-bottom:24px}
.closing-section{padding:68px 0 70px;background:#f2dc79;border-block:1px solid #ddc564;overflow:hidden}.closing-inner{text-align:center;position:relative}.closing-inner .eyebrow{color:var(--ink);margin-bottom:20px}.closing-inner h2{font-size:clamp(37px,4.5vw,60px);line-height:1.12;margin-bottom:27px}.closing-inner>p:last-of-type{font-size:11px;color:#59553e;margin:17px 0 0}.closing-doodle{position:absolute;right:7%;top:30%;width:80px;height:80px;fill:none;stroke:var(--blue);stroke-width:1.4;stroke-linecap:round;transform:rotate(12deg)}footer{background:var(--sheet);padding:31px 0}.footer-row{display:flex;justify-content:space-between;align-items:center;gap:25px}.footer-brand{font-family:var(--serif);font-size:23px;letter-spacing:-.05em;font-weight:700;line-height:1}.footer-brand>span{display:block;font-family:var(--sans);letter-spacing:.18em;font-size:8px;margin-top:8px;font-weight:400}.footer-row>p{font-family:var(--serif);font-size:14px;font-style:italic;color:var(--muted);margin:0}.footer-row>span:last-child{font-size:10px;color:var(--muted)}
@keyframes float-ion{from{transform:translate(-5px,-4px) rotate(-4deg)}to{transform:translate(7px,5px) rotate(4deg)}}
@media(min-width:1600px){.hero-grid{padding-block:90px}}
@media(max-width:1050px){.wrap{width:calc(100% - 56px)}.hero-grid{gap:45px;padding-block:65px}h1{font-size:73px}.question-paper{padding:26px}.question-paper h2{font-size:29px}nav{gap:19px}.lesson-panel{gap:36px}.lesson-body{padding:34px}.faq-grid{gap:60px}.inside-grid{gap:32px}.closing-doodle{right:0}}
@media(max-width:800px){.wrap{width:calc(100% - 40px)}.preview-label{padding-inline:20px}.preview-local{display:none}.nav-row{min-height:74px}.brand img{width:165px;height:48px}.menu-toggle{display:flex}#main-nav{display:none;position:absolute;top:74px;left:0;right:0;background:var(--sheet);border-bottom:1px solid var(--line);padding:15px 20px 22px;flex-direction:column;align-items:stretch;gap:0}#main-nav.is-open{display:flex}#main-nav>a{padding:13px 10px;min-height:44px}.nav-cta{margin-top:10px;justify-content:space-between}.hero-grid{grid-template-columns:1fr;gap:40px;max-width:610px;padding:53px 0}.hero-copy{max-width:540px}h1{font-size:clamp(63px,10vw,83px)}.intro,.hero-description{max-width:490px}.hero-art{max-width:500px;margin-inline:auto;width:100%;padding-inline:17px}.question-paper h2{font-size:34px}.sticky-note{margin-left:35px;margin-right:25px}.hero-foot{flex-wrap:wrap;gap:8px 16px;padding-block:18px}.foot-end{width:100%;margin:0}.section-space{padding:62px 0}.section-heading{align-items:flex-start;flex-direction:column;gap:20px;margin-bottom:32px}.section-heading>p{max-width:500px;font-size:14px}.method-list{grid-template-columns:repeat(2,1fr)}.method-list li{padding:25px 22px!important}.method-list li:nth-child(3){border-left:0}.method-list li:nth-child(-n+2){border-bottom:1px solid var(--line)}.method-list p{max-width:235px}.lesson-panel{grid-template-columns:1fr;gap:25px;min-height:0}.lesson-copy h3{font-size:34px}.diagram-card,.memory-demo{max-width:440px;width:100%;margin-inline:auto}.lesson-tabs button{gap:8px;padding:15px 8px;font-size:12px}.lesson-body{padding:30px}.lesson-bottom{padding:17px 20px;gap:12px}.lesson-hint{display:none}.inside-grid{grid-template-columns:1fr;gap:28px}.inside-grid article{display:grid;grid-template-columns:40px 1fr;gap:0 15px;padding-top:22px}.sketch-icon{grid-row:1/3;margin:3px 0}.inside-grid h3{font-size:25px}.inside-grid p{max-width:520px}.availability-note{margin-top:30px}.faq-grid{grid-template-columns:1fr;gap:22px}.faq-note{display:none}.faq-grid h2{margin-bottom:15px}.closing-doodle{width:42px;height:42px;right:-8px;top:-20px}.footer-row{flex-wrap:wrap;gap:22px}.footer-row>span:last-child{width:100%;border-top:1px solid var(--line);padding-top:18px}}
@media(max-width:420px){.wrap{width:calc(100% - 34px)}.preview-label{font-size:8px;gap:9px;padding-inline:17px}.hero-grid{padding-top:42px;gap:29px}h1{font-size:63px}.eyebrow{font-size:9px}.hero-copy .eyebrow{letter-spacing:.1em}.intro{font-size:17px}.hero-actions{gap:15px;margin-top:25px}.hero-actions .button{width:100%;justify-content:space-between}.hero-art{padding-inline:7px}.question-paper{padding:23px 20px}.question-paper h2{font-size:29px}.paper-meta{font-size:8px}.sticky-note{margin-inline:15px;padding:17px 21px}.memory-title{font-size:38px}.paper-bottom{font-size:8px}.paper-bottom svg{width:30px;flex-shrink:0}.art-caption{font-size:12px}.method-list li{padding:23px 15px!important}.method-list h3{font-size:21px}.method-list p{font-size:12px}.step-arrow{right:13px}.lesson-top{padding:15px 16px;font-size:8px;gap:8px}.lesson-tabs button{flex-direction:column;gap:3px;font-size:11px;padding:12px 5px}.lesson-tabs button span{font-size:12px}.lesson-body{padding:25px 20px}.lesson-copy h3{font-size:30px}.lesson-copy>p:not(.eyebrow){font-size:13px}.diagram-card{padding:18px}.lesson-bottom{padding:14px 16px}.lesson-bottom .button{font-size:11px;padding-inline:13px;gap:12px}.lesson-bottom .text-button{font-size:11px;gap:7px}.demo-caption{font-size:14px}.closing-section{padding-block:57px}.closing-inner h2{font-size:37px}.footer-row>p{font-size:12px}.footer-brand{font-size:21px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}


/* ROY: methyl orange colour demonstration */
.roy-red{color:#a12b32}.roy-orange{color:#87400c}.roy-yellow{color:#605200}
.roy-title{display:flex;gap:18px;font-size:65px;line-height:1.1;margin-block:8px 15px}
.roy-title>span{font-style:normal}.roy-key{justify-content:space-between;gap:12px}
.beaker{position:relative;width:140px;height:157px;margin:28px auto 22px;border:2px solid #4c5147;border-top:0;border-radius:0 0 23px 19px;isolation:isolate}
.beaker::before{content:"";position:absolute;left:-7px;right:-7px;top:-4px;height:7px;border:2px solid #4c5147;border-radius:50%;background:var(--sheet);z-index:3}
.beaker-liquid{position:absolute;bottom:3px;left:3px;right:3px;height:106px;background:#d94b50;border-radius:45% 40% 17px 14px / 6% 6% 17px 14px;transition:background-color .35s ease;box-shadow:inset 12px 0 0 #ffffff25,inset -9px 0 0 #00000009}
.beaker-liquid[data-colour="orange"]{background:#ed902d}.beaker-liquid[data-colour="yellow"]{background:#f0d13f}.unknown-liquid{background:#e7e3d6}
.beaker-marks{position:absolute;right:0;top:25px;width:23px;height:93px;background:repeating-linear-gradient(transparent 0,transparent 21px,#4c5147aa 21px,#4c5147aa 22px)}
.beaker-question{position:absolute;inset:56px 0 auto;text-align:center;font:56px var(--serif);color:var(--blue)}
.direction-strip{display:flex;align-items:center;justify-content:center;gap:30px;font-size:12px}.direction-strip>span:nth-child(2){font-size:26px;line-height:1;color:var(--blue)}
.roy-letters{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:30px 0 18px;font:76px/1 var(--serif);letter-spacing:-.035em}
.roy-letters small{display:block;font:13px/1.4 var(--sans);letter-spacing:0;margin-top:12px;color:var(--ink)}
.roy-swatches{display:grid;grid-template-columns:repeat(3,1fr);gap:13px;margin-bottom:20px}
.roy-swatches span{height:12px;border-radius:50% 30% 40% 30% / 15% 20% 18% 15%;background:#d94b50}.roy-swatches span:nth-child(2){background:#ed902d}.roy-swatches span:nth-child(3){background:#f0d13f;border:1px solid #938017}
.memory-demo .memory-rule{margin-top:25px}
@media(max-width:420px){.roy-title{font-size:58px}.roy-letters{font-size:65px}.memory-demo{padding:26px 23px}.roy-letters small{font-size:12px}}
@media(prefers-reduced-motion:reduce){.beaker-liquid{transition:none}}
/* Simple practical: predict, add the reagent, remember ROY. */
.hero-tubes{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;text-align:center;margin:29px 0 15px;padding:13px 0 18px;background:repeating-linear-gradient(transparent 0,transparent 27px,#d9d3c53d 28px)}
.hero-tubes strong,.hero-tubes small{display:block}.hero-tubes strong{font:italic 17px var(--serif);margin-top:15px}.hero-tubes small{font-size:11px;color:var(--muted);margin-top:5px}
.mini-tube{height:117px;width:42px;border:1.5px solid #657066;border-top:3px double #657066;border-radius:3px 3px 22px 22px;position:relative;margin:auto;background:linear-gradient(to bottom,transparent 38%,#e0e6dd9c 39%,#e0e6dd9c 100%);box-shadow:inset 5px 0 0 #ffffffcc}
.mini-tube span{position:absolute;inset:51px 0 auto;font:28px var(--serif);color:var(--blue)}
.question-paper .paper-bottom{margin-top:23px}.simple-method{grid-template-columns:repeat(3,1fr)}
.experiment{border:1px solid #cbc3b3;background:var(--sheet);box-shadow:5px 6px 0 #e8e1d4;padding:30px 35px 25px}
.experiment-question{display:flex;justify-content:space-between;gap:26px;border-bottom:1px solid var(--line);padding-bottom:23px;align-items:flex-start}
.experiment-question .eyebrow{font-size:9px;margin-bottom:12px}.experiment-question h3{font:26px/1.35 var(--serif);letter-spacing:-.025em;max-width:760px;margin:0}
.question-marks{font-size:12px;white-space:nowrap;color:var(--muted);padding-top:30px}
.reagent-bar{display:flex;align-items:center;gap:16px;padding:22px 0}.reagent-bar strong,.reagent-bar>div>span{display:block}.reagent-bar strong{font-size:14px}.reagent-bar>div>span{font-size:12px;color:var(--muted);margin-top:2px}.reagent-bar .text-button{margin-left:auto;font-size:12px}
.reagent-bottle{width:32px;height:40px;margin-top:7px;position:relative;background:#dba853;border:1.5px solid #665334;border-radius:6px 6px 7px 7px;flex-shrink:0;display:grid;place-items:center}
.reagent-bottle::before{content:"";position:absolute;top:-8px;left:7px;width:15px;height:9px;border-radius:2px;background:#44473e}.reagent-bottle>span{background:#fff9e5;width:100%;font:9px/18px var(--sans);text-align:center;border-block:1px solid #66533455}
.tube-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px}
.tube-card{background:#f8f7ef;border:1px solid var(--line);padding:19px 20px 14px;min-width:0;position:relative}
.tube-heading{display:flex;gap:10px;align-items:flex-start;min-height:51px}.tube-letter{font:italic 18px/1 var(--serif);color:var(--blue);padding:2px 0}.tube-heading h4{font:600 14px/1.45 var(--sans);margin:0 0 3px}.tube-heading p{font-size:12px;margin:0;color:var(--muted)}
.tube-visual{position:relative;width:130px;height:242px;margin:0 auto 5px}
.test-tube{position:absolute;top:83px;left:38px;width:55px;height:143px;border:1.6px solid #5a6d67;border-top:0;border-radius:0 0 29px 27px;background:#fcffff88;overflow:hidden;box-shadow:inset 4px 0 0 #fff9,inset -4px 0 0 #859c9620;isolation:isolate}
.tube-visual::after{content:"";position:absolute;top:80px;left:35px;width:58px;height:6px;border:1.5px solid #5a6d67;border-radius:50%;background:#fffcf5;z-index:4}
.tube-liquid{position:absolute;bottom:3px;left:3px;right:3px;height:87px;border-radius:45% 45% 24px 22px / 4% 4% 24px 22px;background:#dfe8e399;transition:background-color .65s ease;box-shadow:inset 6px 0 0 #fff3,inset -4px 0 0 #00000009}
.tube-liquid[data-colour=red]{background:#dc4a50}.tube-liquid[data-colour=orange]{background:#ee9134}.tube-liquid[data-colour=yellow]{background:#f0d341}
.tube-liquid::after{content:"";position:absolute;inset:0;border-top:2px solid #fff9;border-radius:inherit;opacity:0}.has-reagent .tube-liquid::after{animation:liquid-mix .7s ease-out}
.tube-shine{position:absolute;top:10px;bottom:22px;left:8px;width:4px;background:#ffffff9c;border-radius:3px}.tube-mark{position:absolute;right:0;top:27px;width:10px;height:77px;background:repeating-linear-gradient(transparent 0,transparent 15px,#59726a99 15px,#59726a99 16px)}
.tube-shadow{position:absolute;bottom:6px;left:25px;width:82px;height:9px;border-radius:50%;background:#b7b4a72e}
.dropper{position:absolute;left:55px;top:0;width:21px;height:58px;opacity:0;transform:translateY(-10px);z-index:5}
.dropper-bulb{position:absolute;top:0;left:1px;width:18px;height:25px;background:#30372f;border-radius:10px 10px 4px 4px}.dropper-stem{position:absolute;top:24px;left:6px;width:8px;height:30px;background:linear-gradient(to right,#fff 0 35%,#eaba62 36% 65%,#d9e4dd 66%);border:1px solid #637166;clip-path:polygon(0 0,100% 0,75% 100%,25% 100%)}
.reagent-drop{position:absolute;left:62px;top:54px;width:7px;height:10px;background:#d78e2d;border-radius:55% 55% 55% 55%;opacity:0;z-index:3;transform:scale(.3)}
.is-adding .dropper{animation:dropper-enter 1.65s ease both}.is-adding .reagent-drop{animation:drop-fall .55s ease-in both}.is-adding .drop-one{animation-delay:.28s}.is-adding .drop-two{animation-delay:.52s}.is-adding .drop-three{animation-delay:.76s}


.tube-result{font-size:12px;line-height:1.6;min-height:88px;margin:11px 0 0;color:#62645d}.tube-result.correct .result-answer{color:#315c43}.result-answer{display:block;font-weight:700}.result-reason{display:block;margin-top:4px;color:var(--muted);font-weight:400}.experiment-progress{text-align:center;font-size:12px;color:var(--muted);margin:20px 0 0}
.roy-reveal{display:grid;grid-template-columns:1fr 1fr;gap:18px 30px;align-items:center;margin-top:22px;padding:28px 33px 19px;background:#f4df84;border:1px solid #d8c16d;animation:memory-enter .4s ease}
.roy-reveal .eyebrow{font-size:9px;margin-bottom:8px;color:#49503d}.roy-reveal h3{font:36px/1.1 var(--serif);letter-spacing:-.04em;margin-bottom:13px}.roy-reveal-copy>p:last-child{font-size:13px;line-height:1.7;margin-bottom:0}.roy-memory{display:grid;grid-template-columns:repeat(3,1fr);text-align:center;font:68px/1 var(--serif);gap:15px}.roy-memory small{display:block;font:12px/1.5 var(--sans);margin-top:10px;color:var(--ink)}.roy-accuracy{grid-column:1/-1;border-top:1px solid #b7a66388;padding-top:14px;margin:0;font-size:12px;color:#57533f}
@keyframes dropper-enter{0%{opacity:0;transform:translateY(-14px)}15%,80%{opacity:1;transform:translateY(0)}100%{opacity:0;transform:translateY(-14px)}}
@keyframes drop-fall{0%{opacity:0;transform:translateY(0) scale(.4)}10%{opacity:1;transform:translateY(0) scale(1)}92%{opacity:1;transform:translateY(78px) scale(.8,1.4)}100%{opacity:0;transform:translateY(87px) scale(2,.3)}}
@keyframes liquid-mix{0%{opacity:1;transform:scale(.6,1.1)}100%{opacity:0;transform:scale(1,1)}}
@keyframes memory-enter{from{opacity:0;transform:translateY(7px)}to{opacity:1;transform:none}}
@media(max-width:1050px){.experiment{padding:25px}.tube-grid{gap:12px}.tube-card{padding:17px 15px}.tube-heading h4{font-size:14px}.roy-memory{font-size:61px}}
@media(max-width:800px){.experiment{padding:23px 18px}.experiment-question h3{font-size:23px}.question-marks{padding-top:28px;font-size:11px}.tube-grid{grid-template-columns:1fr;gap:15px}.tube-card{display:grid;grid-template-columns:120px 1fr;column-gap:20px;padding:18px 20px}.tube-visual{grid-column:1;grid-row:1/3;align-self:center;margin:-10px auto -4px;height:235px;width:120px}.tube-heading{grid-column:2;min-height:0;margin-bottom:16px;align-self:end}.tube-controls{grid-column:2}.tube-heading h4{font-size:14px}.tube-heading p{font-size:12px}.tube-result{min-height:88px}.roy-reveal{padding:24px 23px 17px;gap:23px}.roy-reveal h3{font-size:30px}.roy-memory{font-size:57px;gap:9px}.simple-method{grid-template-columns:repeat(3,1fr)}.simple-method li{padding:24px 17px!important;border-bottom:0!important}.simple-method li:nth-child(3){border-left:1px solid var(--line)}.simple-method h3{font-size:22px}.simple-method .step-arrow{display:none}}
@media(max-width:480px){.experiment{padding:20px 12px}.experiment-question{gap:10px;display:block;padding-inline:4px;padding-bottom:18px}.experiment-question h3{font-size:22px}.question-marks{display:block;text-align:right;padding-top:10px}.reagent-bar{gap:12px;padding:22px 5px;flex-wrap:wrap}.reagent-bar .text-button{padding:0;min-height:44px;font-size:12px}.reagent-bar strong{font-size:13px}.reagent-bar>div>span{font-size:12px}.tube-card{grid-template-columns:81px minmax(0,1fr);gap:0 13px;padding:17px 12px}.tube-visual{width:81px;transform:translateX(-22px);margin-right:-30px;pointer-events:none}.tube-heading{gap:7px;margin-bottom:12px}.tube-heading h4{font-size:14px}.tube-heading p{font-size:12px}.tube-letter{font-size:16px}.tube-result{font-size:12px;min-height:88px}.roy-reveal{grid-template-columns:1fr;padding:22px 20px 17px;gap:20px;text-align:center}.roy-memory{font-size:67px}.roy-accuracy{text-align:left;font-size:12px}.simple-method{grid-template-columns:1fr}.simple-method li{border-left:0!important;border-bottom:1px solid var(--line)!important;display:grid;grid-template-columns:36px 1fr;gap:0 14px}.simple-method li:last-child{border-bottom:0!important}.simple-method .step-number{grid-row:1/3}.simple-method h3{margin-bottom:6px}.simple-method p{max-width:none}.hero-tubes{gap:12px}.mini-tube{height:105px}.mini-tube span{inset:43px 0 auto}}
@media(max-width:480px){.tube-visual{transform:none;margin:-10px 0 -4px}.test-tube{left:12px}.tube-visual::after{left:9px}.dropper{left:29px}.reagent-drop{left:36px}.tube-shadow{left:0}}
@media(prefers-reduced-motion:reduce){.tube-liquid{transition:none}.roy-reveal,.has-reagent .tube-liquid::after,.is-adding .dropper,.is-adding .reagent-drop{animation:none}}

/* A short recall check completes the learning loop. */
.skip-link{clip-path:inset(50%)}.skip-link:focus{clip-path:none}
.recall-check{display:grid;grid-template-columns:1fr 1fr;gap:28px 48px;align-items:center;border-top:1px dashed #b6b09f;margin-top:28px;padding:28px 5px 4px}
.recall-check .eyebrow{margin-bottom:9px;font-size:10px}
.recall-check h3{font:30px/1.2 var(--serif);letter-spacing:-.035em;margin-bottom:12px}
.recall-copy>p:last-child{font-size:14px;line-height:1.75;margin:0;max-width:425px}
.recall-options{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px}
.recall-options button{min-height:48px;padding:10px 8px;background:var(--sheet);border:1px solid #aaa999;border-radius:3px;font-size:14px}
.recall-options button:hover:not(:disabled){border-color:var(--blue);background:#edf0e9}
.recall-options button.is-wrong{border-color:#8b622b;background:#f5e9cc}
.recall-options button.is-correct{border:2px solid var(--green);background:#e9f0e4;color:var(--green);font-weight:700}
.recall-options button:disabled{opacity:1;color:var(--muted)}
.recall-options button.is-correct:disabled{color:var(--green)}
.recall-feedback{font-size:13px;line-height:1.7;min-height:66px;color:var(--muted);margin:14px 0 0}
.recall-feedback.correct{color:var(--green)}
.method-section{padding:42px 0;border-bottom:1px solid var(--line)}
.method-heading{display:flex;justify-content:space-between;gap:24px;align-items:baseline;margin-bottom:24px}
.method-heading .eyebrow{margin:0}
.method-heading h2{font-size:27px;letter-spacing:-.035em;margin:0}
.simple-method{border:0}
.simple-method li{display:grid;grid-template-columns:32px 1fr;gap:0 12px;padding:12px 24px 12px 0}
.simple-method li+li{padding:12px 24px}
.simple-method .step-number{grid-row:1/3;margin:2px 0 0}
.simple-method h3{font-size:23px;margin-bottom:5px}
.simple-method p{max-width:none}
.simple-method .step-arrow{display:none}
@media(max-width:800px){
  .recall-check{grid-template-columns:1fr;gap:20px}
  .recall-copy>p:last-child{max-width:none}
  .method-heading{display:block}
  .method-heading .eyebrow{margin-bottom:12px}
  .simple-method{grid-template-columns:1fr}
  .simple-method li,.simple-method li+li{padding:18px 0!important;border-left:0!important;border-bottom:1px solid var(--line)!important}
  .simple-method li:last-child{border-bottom:0!important;padding-bottom:0!important}
}
@media(max-width:480px){
  .recall-check{padding-inline:5px}
  .recall-options{gap:7px}
  .recall-feedback{min-height:88px}
  
  .reagent-bar .text-button{margin-left:48px}
}


/* One tap predicts the colour and starts the experiment. */
.prediction-label{font-size:12px;font-weight:700;margin:0 0 9px}
.colour-options{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:7px}
.colour-choice{min-height:48px;border:1px solid #aaa999;border-radius:3px;background:var(--sheet);font-size:13px;padding:10px 6px;display:flex;align-items:center;justify-content:center;gap:6px}
.colour-dot{width:9px;height:9px;border-radius:50%;flex-shrink:0;background:var(--swatch);border:1px solid #0003}
.colour-choice[data-prediction=red]{--swatch:#dc4a50;background:#fcf0ee}
.colour-choice[data-prediction=orange]{--swatch:#ee9134;background:#fbefdf}
.colour-choice[data-prediction=yellow]{--swatch:#f0d341;background:#f9f4d9}
.colour-choice:hover:not(:disabled){border-color:var(--ink);box-shadow:inset 0 0 0 1px var(--ink)}
.colour-choice:disabled{opacity:1;color:var(--muted)}
.colour-choice[aria-pressed=true]{border-color:var(--ink);box-shadow:inset 0 0 0 1px var(--ink);font-weight:700;color:var(--ink)}
@media(max-width:1050px) and (min-width:801px){.colour-options{grid-template-columns:1fr}.colour-choice{justify-content:flex-start;padding-inline:14px}}
@media(max-width:480px){.colour-options{grid-template-columns:1fr;gap:6px}.colour-choice{justify-content:flex-start;padding-inline:12px;font-size:14px}}

/* Show the chemistry first, then reveal the book's memory cue. */
.inside-grid p{font-size:14px;line-height:1.75}
.book-author{margin:28px 0 0;font-size:12px;color:var(--muted)}
.book-author+.availability-note{margin-top:20px}

/* A quiet reading desk, with a curved, physical page turn. */
.book-reader{margin:36px 0 0;padding:28px 32px 24px;background:var(--paper);border-block:1px solid var(--line)}
.reader-heading{display:flex;align-items:center;justify-content:space-between;gap:24px}
.reader-heading .eyebrow{margin:0 0 9px;font-size:9px}
.reader-heading h3{font:34px/1.2 var(--serif);letter-spacing:-.025em;margin:0}
.reader-hint{font:italic 16px/1.6 var(--serif);color:var(--blue);margin:0}
.book-stage{max-width:960px;margin:22px auto 0;padding:18px 0 28px;overflow:hidden}
.flipbook{width:100%;max-width:840px;min-width:0!important;margin:auto;filter:drop-shadow(0 18px 16px #342f2725)}
.book-reader.is-interactive .flipbook{transition:transform .85s cubic-bezier(.25,.7,.25,1)}
.book-reader.is-ready[data-mode=landscape][data-position=front] .flipbook{transform:translateX(-25%)}
.book-reader.is-ready[data-mode=landscape][data-position=back] .flipbook{transform:translateX(25%)}
.book-reader:not(.is-ready) .flipbook{max-width:390px}
.book-reader:not(.is-ready) .flip-leaf:not(:first-child){display:none}
.flip-leaf{position:relative;background:#fffefa;border:1px solid #d6d0c3;overflow:hidden;user-select:none}
.flip-leaf img{width:100%;height:100%;object-fit:contain;pointer-events:none;user-select:none;-webkit-user-drag:none;background:white}
.flip-leaf::after{content:"";position:absolute;inset:0;pointer-events:none;background:linear-gradient(90deg,#332b2115,transparent 8%,transparent 96%,#332b2108)}
.flip-leaf.--left::after{background:linear-gradient(90deg,#332b2108,transparent 4%,transparent 92%,#332b2125)}
.flip-cover{border-color:#a4a3a0;background:#102c48}
.leaf-content{height:100%;padding:11% 10%;display:flex;flex-direction:column;color:#23334a}
.leaf-kicker{font-size:9px;font-weight:700;letter-spacing:.13em;margin:0 0 25px;color:var(--blue)}
.leaf-content h3{font:clamp(25px,3vw,40px)/1.14 var(--serif);letter-spacing:-.035em;margin:0}
.leaf-rule{width:44px;height:3px;background:var(--yellow);margin:24px 0}
.leaf-content>p:not([class]){font-size:14px;line-height:1.8;margin:0 0 20px}
.leaf-content ol{list-style:none;padding:0;margin:7px 0 20px}
.leaf-content li{display:flex;gap:15px;align-items:center;padding:10px 0;border-bottom:1px solid var(--line);font:16px/1.4 var(--serif)}
.leaf-content li span{font:italic 17px/1 var(--serif);color:var(--blue)}
.leaf-footnote{margin:auto 0 0;font-size:10px;line-height:1.65;color:var(--muted)}
.flip-end{background:#122f4a;color:white}
.flip-end .leaf-content{color:#fffdf7}
.flip-end .leaf-kicker,.flip-end .leaf-footnote{color:#d7e1e8}
.leaf-signature{font:32px/1.2 var(--serif);margin:20px 0}
.leaf-signature span{font:italic 16px/1.5 var(--serif);color:#eed989}
.reader-controls{display:grid;grid-template-columns:140px minmax(0,1fr) 140px;gap:14px;align-items:center;max-width:660px;margin:0 auto}
.reader-nav{display:flex;align-items:center;justify-content:center;gap:12px;min-height:46px;padding:10px 16px;border:1px solid #aaa797;background:var(--sheet);border-radius:3px;font-size:13px}
.reader-nav:hover:not(:disabled){border-color:var(--blue);background:#eeede4}
.reader-nav-next{background:var(--ink);border-color:var(--ink);color:var(--sheet)}
.reader-nav-next:hover:not(:disabled){background:#3b4136;border-color:#3b4136}
.reader-nav[aria-disabled=true]{cursor:default}
.reader-status{font:15px/1.5 var(--serif);margin:0;text-align:center;color:var(--ink)}
.reader-gesture{font-size:11px;color:var(--muted);text-align:center;margin:17px 0 2px}
.reader-read-links{display:flex;justify-content:center;align-items:center;flex-wrap:wrap;gap:4px 18px;font-size:12px;min-height:44px;margin:8px auto 0}
.reader-read-links>span{color:var(--muted)}
.reader-read-links a{display:inline-flex;gap:9px;align-items:center;color:var(--blue);min-height:44px;text-decoration:underline;text-underline-offset:4px}
.reader-sample-note{font-size:11px;color:var(--muted);text-align:center;margin:4px 0 0}
.book-reader.is-reduced .book-stage{pointer-events:none}
.book-reader.is-reduced .flipbook{transition:none}
.book-purchase{margin:28px auto 42px;max-width:320px;text-align:center}
.book-get-link{display:flex;align-items:center;justify-content:space-between;gap:20px;min-height:52px;padding:13px 22px;background:var(--blue);color:white;border:1px solid #193e7d;border-radius:3px;box-shadow:2px 3px 0 #d9d2c3;font:700 14px/1.6 var(--sans)}
.book-get-link:hover{background:#1c4387}
.book-get-link>span{font-size:21px;font-weight:400}
.book-purchase>p{font-size:11px;line-height:1.65;color:var(--muted);margin:11px 0 0}
.book-viewer-open{overflow:hidden}
.page-viewer{width:min(960px,calc(100% - 32px));max-width:none;max-height:calc(100dvh - 32px);padding:0;border:1px solid var(--line);background:var(--paper);color:var(--ink);box-shadow:0 20px 80px #0004}
.page-viewer::backdrop{background:#22251fcc}
.page-viewer[open]{display:flex;flex-direction:column}
.page-viewer-header{display:flex;align-items:center;justify-content:space-between;gap:18px;flex-shrink:0;padding:16px 24px;border-bottom:1px solid var(--line)}
.page-viewer-header h2{font-size:25px;letter-spacing:-.025em;line-height:1.2;margin:0 0 4px}
.page-viewer-header p{font-size:12px;color:var(--muted);margin:0}
.page-viewer-close{display:flex;align-items:center;justify-content:center;gap:14px;min-height:44px;background:var(--sheet);border:1px solid #89897e;padding:9px 14px;font-size:13px;flex-shrink:0}
.page-viewer-close:hover{background:var(--yellow)}
.page-viewer-close span{font-size:22px;line-height:1}
.page-viewer-scroll{overflow:auto;overscroll-behavior:contain;padding:24px;min-height:0}
.page-viewer-image{width:100%;height:auto;background:white;box-shadow:0 2px 8px #0001}
.page-viewer-image.is-zoomed{width:1200px;max-width:none}
.page-viewer-tools{display:flex;align-items:center;gap:16px;padding:0 24px;border-bottom:1px solid var(--line);flex-shrink:0;font-size:12px;color:var(--muted)}
.page-viewer-zoom{min-height:44px;border:0;background:none;padding:8px 0;color:var(--blue);font-size:13px;font-weight:700;text-decoration:underline;text-underline-offset:4px}

@media(max-width:800px){
 .book-reader{padding:25px 18px 22px}
 .reader-heading{display:block;text-align:center}.reader-heading h3{font-size:30px}.reader-hint{margin-top:10px;font-size:15px}
 .reader-controls{grid-template-columns:110px minmax(0,1fr) 110px;gap:8px}.reader-nav{padding:10px 8px;gap:7px;font-size:12px}
}
@media(max-width:600px){
 .book-reader{padding:22px 12px}.book-stage{margin-top:18px;padding:10px 0 24px}
 .reader-controls{grid-template-columns:1fr 1fr;gap:10px}.reader-status{grid-column:1/-1;grid-row:1;font-size:16px;margin-bottom:5px}.reader-nav{min-height:46px;font-size:13px}
 .reader-gesture{font-size:10px}.reader-read-links{gap:0 15px}.reader-sample-note{font-size:10px}
 .leaf-content{padding:9%}.leaf-kicker{font-size:8px;margin-bottom:17px}.leaf-rule{margin:17px 0}.leaf-content>p:not([class]){font-size:12px;margin-bottom:10px}.leaf-content li{font-size:14px;padding:8px 0}.leaf-footnote{font-size:8px}.leaf-signature{font-size:28px;margin:13px 0}
 .page-viewer{width:calc(100% - 16px);max-height:calc(100dvh - 16px)}.page-viewer-header{padding:14px;gap:10px}.page-viewer-header h2{font-size:22px}.page-viewer-header p{font-size:11px}.page-viewer-close{padding:8px 10px;gap:8px}.page-viewer-scroll{padding:10px}.page-viewer-tools{padding-inline:14px}
}
.mini-red{--mini-liquid:#dc4a50}.mini-orange{--mini-liquid:#ee9134}.mini-yellow{--mini-liquid:#f0d341}
.mini-tube{background:linear-gradient(to bottom,transparent 38%,var(--mini-liquid) 39%,var(--mini-liquid) 100%)}
.indicator-heading{display:flex;align-items:center;gap:18px;margin-bottom:26px}
.indicator-heading .reagent-bottle{margin:0 0 0 3px}
.indicator-heading .eyebrow{margin:0 0 6px;font-size:10px}
.indicator-heading h3{font:30px/1.25 var(--serif);letter-spacing:-.025em;margin:0}
.indicator-demo .tube-grid{grid-template-columns:repeat(3,minmax(0,1fr));gap:0;border:1px solid var(--line);background:#f8f7ef}
.indicator-demo .tube-card{display:block;padding:24px 8px 20px;border:0;background:none;text-align:center}
.indicator-demo .tube-card+.tube-card{border-left:1px solid var(--line)}
.indicator-demo .tube-heading{display:block;min-height:0;margin:0}
.indicator-demo .tube-heading h4{font:600 16px/1.4 var(--sans);margin:0 0 3px}
.indicator-demo .tube-heading p{font-size:12px;margin:0}
.indicator-demo .tube-visual{width:88px;height:180px;margin:17px auto 8px;transform:none}
.indicator-demo .test-tube{top:14px;left:17px}
.indicator-demo .tube-visual::after{top:11px;left:14px}
.indicator-demo .tube-shadow{left:3px;bottom:11px;width:82px}
.observed-colour{font:26px/1.2 var(--serif);margin:0}
.indicator-note{font-size:13px;line-height:1.7;text-align:center;color:var(--muted);margin:19px auto 0;max-width:540px}
.hack-prompt{text-align:center;margin:27px 0 12px}
.hack-prompt p{font:25px/1.3 var(--serif);letter-spacing:-.02em;margin:0 0 4px}
.hack-prompt>span{font:25px/1 var(--serif);color:var(--blue)}
.hack-reveal{border:0}
.hack-reveal summary{width:fit-content;max-width:100%;margin:0 auto;padding:13px 24px;min-height:50px;gap:20px;justify-content:center;border:1px solid var(--ink);border-radius:3px;background:var(--ink);color:var(--sheet);font:700 14px/1.5 var(--sans)}
.hack-reveal summary:hover{background:#3b4136}
.hack-reveal summary>span{font:inherit;color:inherit;transform:none}
.hack-reveal[open] summary>span{transform:none}
.hack-reveal summary .reveal-symbol{font-size:22px;font-weight:400;line-height:1}
.hack-reveal .reveal-open,.hack-reveal[open] .reveal-closed{display:none}
.hack-reveal[open] .reveal-open{display:inline}
.hack-reveal[open] .reveal-symbol{transform:rotate(45deg)}
.hack-reveal .roy-reveal{margin-top:25px}
.titration-note{grid-column:1/-1;background:#fff8dd;border-left:3px solid #875c14;padding:13px 16px;margin:0;font-size:13px;line-height:1.7;text-align:left;color:var(--ink)}
.book-connection{grid-column:1/-1;display:flex;align-items:center;justify-content:space-between;gap:20px;border-top:1px solid #b7a66388;padding-top:19px}
.book-connection p{font-size:13px;line-height:1.8;margin:0}
.book-connection strong{font-weight:700}
.book-connection .text-link{white-space:nowrap;font-weight:700;min-height:44px;align-items:center}
@media(max-width:800px){.book-connection{display:block}.book-connection .text-link{margin-top:10px}}
@media(max-width:480px){
  .indicator-heading{gap:14px;margin:0 4px 23px}
  .indicator-heading h3{font-size:24px}
  .indicator-heading .eyebrow{font-size:9px;letter-spacing:.1em}
  .indicator-demo .tube-card{padding:19px 8px 16px}
  .indicator-demo .tube-heading h4{font-size:12px}
  .indicator-demo .tube-visual{width:68px;height:174px;margin:13px auto 4px}
  .indicator-demo .test-tube{top:10px;left:7px}
  .indicator-demo .tube-visual::after{top:7px;left:4px}
  .indicator-demo .tube-shadow{left:0;width:68px;bottom:9px}
  .observed-colour{font-size:22px}
  .indicator-note{font-size:12px;padding-inline:5px}
  .hack-prompt p{font-size:23px}
  .book-connection{text-align:left}
}

/* A small screening room on the same paper desk. */
.book-film{max-width:900px;margin:52px auto 44px;padding:24px;background:#faf8f0;border:1px solid #d3cbbb;box-shadow:4px 5px 0 #e9e3d6;}
.book-film figcaption{margin-bottom:22px;}
.book-film h3{font-family:Georgia,serif;font-size:clamp(26px,3vw,36px);font-weight:400;margin:8px 0 10px;}
.book-film figcaption>p:last-child{color:#5c625e;line-height:1.6;margin:0;}
.book-film-screen{position:relative;background:#f6f3e9;border:1px solid #d3cbbb;}
.book-film video{display:block;width:100%;height:auto;aspect-ratio:16/9;}
.book-film-play{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;flex-direction:column;gap:12px;border:0;background:rgba(249,247,239,.22);color:#fff;cursor:pointer;}
.book-film-play[hidden]{display:none;}
.book-film-play>span:first-child{display:grid;place-items:center;padding-left:4px;width:68px;height:68px;background:#173e59;border:2px solid #faf8f0;border-radius:50%;box-shadow:3px 4px 0 rgba(23,62,89,.25);font-size:26px;}
.film-play-label{padding:7px 12px;background:#173e59;border-radius:2px;font:600 14px/1.4 Arial,sans-serif;}
.book-film-play:hover>span:first-child{background:#245f86;}
.book-film-play:focus-visible{outline:3px solid #2063a3;outline-offset:5px;}
.book-film-note{font-size:13px;color:#5c625e;text-align:center;margin:14px 0;}
.book-film-summary{font-size:13px;line-height:1.7;color:#444b45;}
.book-film-summary summary{cursor:pointer;text-decoration:underline;text-underline-offset:4px;}
.book-film-summary p{max-width:75ch;margin:12px 0 0;}
@media(max-width:600px){.book-film{padding:14px;margin:36px auto;}.book-film-play>span:first-child{width:48px;height:48px;font-size:20px;}.film-play-label{font-size:12px;}.book-film figcaption{margin-bottom:16px;}}

/* Links back to the main YourStudyHack collection. */
.footer-row nav{display:flex;flex-wrap:wrap;gap:18px;font-size:12px}.footer-row nav a{color:inherit;text-underline-offset:4px}.book-get-link{max-width:380px}.availability-note a{color:var(--blue);text-underline-offset:3px}.intro{max-width:510px}
.availability-note a,.reader-sample-note a{text-decoration:underline;text-underline-offset:3px;}
/* Direct ROY cue: large, recognisable letter colours with readable labels. */
.roy-reveal .roy-memory{font-family:Arial,sans-serif;font-size:clamp(80px,9vw,112px);font-weight:800;gap:12px}
.roy-memory .roy-red{color:#d52b35}.roy-memory .roy-orange{color:#f17a12}.roy-memory .roy-yellow{color:#f3c928;-webkit-text-stroke:1px #8d6b00}
.roy-memory small{font-size:14px;font-weight:600;-webkit-text-stroke:0}
@media(max-width:800px){.roy-reveal{grid-template-columns:1fr;text-align:center}.roy-reveal .roy-memory{max-width:440px;width:100%;margin:auto;font-size:clamp(76px,17vw,112px)}}
.roy-memory .roy-condition{display:block;font:400 13px/1.6 Arial,sans-serif;margin-top:5px;color:var(--ink);-webkit-text-stroke:0}
/* The question comes first; the answer and registration follow the reveal. */
.question-reveal-actions{position:absolute;top:53%;left:50%;transform:translateX(-50%);width:min(320px,calc(100% - 30px));z-index:4;text-align:center;pointer-events:auto}.question-reveal-actions p{font:italic 21px/1.4 Georgia,serif;margin:0 0 16px}.question-reveal-actions .button{font-size:14px;min-height:50px;gap:15px;padding:12px 18px;justify-content:center;width:100%}
.book-reader.is-question-hidden .flipbook{pointer-events:none}.book-reader.is-question-hidden .reader-gesture{visibility:hidden}.page-viewer-tools .page-viewer-reveal{background:#f4cf4f;border:1px solid #7c6827;color:#22251f;font-weight:700;padding:10px 14px;min-height:44px}.page-viewer-tools{flex-wrap:wrap}
@media(max-width:500px){.question-reveal-actions{width:calc(100% - 38px)}.question-reveal-actions p{font-size:18px}.question-reveal-actions .button{font-size:12px;padding-inline:10px}}