:root{--navy:#242538;--indigo:#32364e;--text:#272a3a;--muted:#717683;--violet:#6554ad;--lilac:#e5ddfb;--paper:#fffefa;--bg:#f6f4ee;--line:#e3e2dc;--good:#1e765b;--error:#b84f4c}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--text);font-family:Inter,'Avenir Next',Arial,sans-serif}button,input,select{font:inherit}button{cursor:pointer}a{color:inherit;text-decoration:none}button:focus-visible,input:focus-visible,select:focus-visible,a:focus-visible{outline:3px solid #9985e0;outline-offset:3px}.topbar{height:72px;padding:0 max(5vw,22px);background:var(--navy);color:#f5f2ef;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid #4a4e63}.logo{display:flex;align-items:center;gap:12px;font-weight:800;letter-spacing:.115em;font-size:14px}.logo-mark{width:31px;height:31px;background:#d8cafa;color:#3d3563;border-radius:50%;display:grid;place-items:center;font:700 20px Georgia,serif}.logo-light{color:#cfc4ed}.top-link{font-size:13px;font-weight:700}.top-link span{margin-left:6px;color:#d8cafa}.hero{background:var(--navy);color:#fff;min-height:520px;padding:72px max(5vw,22px) 80px;display:grid;grid-template-columns:minmax(0,1fr) minmax(330px,530px);align-items:center;gap:4%;overflow:hidden}.hero-copy{position:relative;z-index:2}.eyebrow{display:flex;align-items:center;gap:11px;color:#cfc5eb;font:700 11px 'Courier New',monospace;letter-spacing:.15em;margin:0}.eyebrow span{width:25px;height:1px;background:#cfc5eb;display:block}.eyebrow.dark{color:#7a71a2}.eyebrow.dark span{background:#8c7fb9}h1,h2,h3,p{margin-top:0}h1{font-size:clamp(50px,6vw,90px);letter-spacing:-.075em;line-height:1.05;margin:27px 0 25px;font-weight:650}h1 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span{position:absolute;bottom:36px;left:4px;font-size:19px}.hero-bond{width:46px;border-top:2px solid #d6c8f5;margin:0 5px}.hero-side{position:absolute;width:2px;height:48px;background:#d6c8f5;top:107px;left:50%}.hero-question{position:absolute;top:165px;left:44%;color:#e3d0a8;font:italic 24px Georgia,serif}.art-label{position:absolute;font:11px 'Courier New',monospace;letter-spacing:.11em;color:#bcb3d8}.art-label-a{right:4%;top:27px}.art-label-b{bottom:2px;left:5%}.practice{max-width:1510px;margin:auto;padding:84px max(5vw,22px) 95px}.section-title{display:flex;justify-content:space-between;align-items:end;gap:20px}.section-title h2{font-size:clamp(38px,4.1vw,60px);letter-spacing:-.065em;margin:14px 0 22px}.progress-label{text-align:right;margin-bottom:25px;display:flex;align-items:baseline;gap:10px;color:#6c7180;font-size:12px}.progress-label strong{font:600 20px 'Courier New',monospace;color:#393b55}.progress-track{height:5px;background:#e5e3dc;border-radius:6px;margin:0 0 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h3{font-size:30px;letter-spacing:-.055em;margin:7px 0 22px}.status-tag{font:700 10px 'Courier New',monospace;letter-spacing:.08em;padding:9px 11px;background:#f0eafd;color:#6d5ca4;white-space:nowrap}.status-tag.done{background:#e3f4eb;color:#28785e}.status-tag.revealed{background:#fff0e6;color:#9e6b49}.structure-frame{border:1px solid #dcdde0;background:#fcfcfb;border-radius:4px;overflow:hidden}.structure-bar{display:flex;justify-content:space-between;align-items:center;padding:12px 16px;border-bottom:1px solid #e8e7e5;color:#7a7d8b;font:700 10px 'Courier New',monospace;letter-spacing:.1em}.structure-bar span:first-child{display:flex;align-items:center;gap:7px}.structure-bar i{width:7px;height:7px;border-radius:50%;background:#a092d6;display:block}.structure{min-height:350px;display:flex;align-items:center;justify-content:center;padding:0 10px;background:radial-gradient(circle at 50% 45%,#fff,#fbfbfa 75%)}.structure svg{width:100%;max-width:680px;height:350px;overflow:visible}.structure-caption{background:#f6f3fa;border-top:1px solid #e8e2f1;padding:11px 16px;display:flex;align-items:center;gap:12px;font-size:12px;color:#6d6880;line-height:1.4}.caption-chip{padding:5px 8px;background:#e7e0f5;color:#6b54a4;border-radius:2px;white-space:nowrap;font-weight:700}.form-heading{display:flex;justify-content:space-between;gap:12px;padding:23px 0 12px;font-size:12px;color:#838491}.fields{display:grid;grid-template-columns:1.2fr .85fr 1fr;gap:11px}.field{display:flex;flex-direction:column;gap:7px;font-size:13px;font-weight:700;color:#46495a}.field input,.field select{width:100%;height:44px;border:1px solid #d8dae0;background:#fff;color:#2d2e3c;padding:0 11px;border-radius:3px;font-size:14px}.field input::placeholder{color:#a4a6b0}.field.ok input,.field.ok select{border-color:#60a58a;background:#f5fcf8}.field.bad input,.field.bad select{border-color:#d47a74;background:#fff9f7}.field small{min-height:31px;font-size:11px;line-height:1.35;font-weight:500;color:#7d7e8d}.field.ok small{color:var(--good)}.field.bad small{color:var(--error)}.form-actions{display:flex;align-items:center;flex-wrap:wrap;gap:16px;margin:10px 0 0}.check-button,.next-button{border:0;background:#4b456d;color:#fff;padding:12px 17px;border-radius:3px;font-size:13px;font-weight:750}.check-button:hover,.next-button:hover{background:#645789}.check-button span,.next-button span{margin-left:14px}.quiet-button{border:0;background:none;color:#6555a5;font-size:13px;font-weight:700;padding:9px 0}.quiet-button:hover{text-decoration:underline}.feedback{font-size:13px;line-height:1.55;color:#5f626f}.feedback:not(:empty){padding:12px 14px;background:#f2f0fa;border-radius:3px;margin-top:14px}.feedback.success{background:#e9f6ed;color:#26654e}.feedback.error{background:#fff0eb;color:#884d42}.feedback.hint{background:#f0eff9;color:#5c5680}.exercise-footer{border-top:1px solid #e8e7e4;padding-top:16px;margin-top:19px;display:flex;align-items:center;justify-content:space-between;gap:20px}.exercise-footer span{font-size:12px;color:#7d7d88;line-height:1.45}.next-button{background:#dbcef9;color:#292640;white-space:nowrap}.next-button:hover{background:#cfc0f4}.method-note{max-width:880px;color:#787c82;font-size:12px;line-height:1.7;margin:25px 0 0}.method-note a{color:#5d4ea0;text-decoration:underline;text-underline-offset:3px}footer{display:flex;justify-content:space-between;gap:16px;background:#242538;color:#c7c7d5;padding:29px max(5vw,22px);font-size:12px}footer span:first-child{font-weight:800;letter-spacing:.1em;color:#ece8fc}.chem-bond{stroke:#44485b;stroke-width:3;stroke-linecap:round}.chem-double{stroke-width:2.4}.chem-side{stroke:#745fb2;stroke-width:3.2;stroke-linecap:round}.chem-text{font:500 27px Georgia,serif;fill:#33394b;text-anchor:middle;dominant-baseline:middle}.chem-side-text{font:500 26px 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60px}.hero-n,.hero-cooh,.hero-alpha{font-size:22px}.hero-bond{width:28px}.hero-side{top:85px;height:43px}.hero-question{top:139px}.art-label-a{display:none}.section-title{display:block}.progress-label{text-align:left;margin-bottom:16px}.practice{padding:60px 17px 80px}.exercise-head h3{font-size:25px}.structure{min-height:295px}.structure svg{height:295px}.structure-bar{font-size:9px}.structure-caption{font-size:11px}.fields{grid-template-columns:1fr}.field small{min-height:15px}.form-heading span:last-child{display:none}.form-actions{gap:10px 18px}.exercise-footer{align-items:start;flex-direction:column}.exercise-footer .next-button{align-self:flex-end}footer span:nth-child(2){display:none}}
.structure{background:#fff}
.structure svg{height:390px}
.chem-side,.chem-ring,.chem-ring-double{stroke:#353a42}
.chem-side-text{fill:#292e38}
.chem-small{display:none}
@media(max-width:620px){.structure{min-height:320px}.structure svg{height:320px}}
.pronunciation{display:flex;align-items:baseline;flex-wrap:wrap;gap:7px 13px;padding:12px 15px;margin:0 0 16px;background:#edf7f1;border-left:3px solid #60a58a;border-radius:3px;color:#245d4b}
.pronunciation[hidden]{display:none}
.pronunciation-label{font:700 10px 'Courier New',monospace;letter-spacing:.12em;color:#487965}
.pronunciation strong{font-size:16px;letter-spacing:.01em}
.pronunciation small{font-size:11px;color:#5f7468;line-height:1.4}

.recognition-notes{max-width:570px;margin:26px 0 0;color:#e6e1f1;font-size:16px;line-height:1.5}.recognition-notes p{margin:0 0 10px}

.recognition-notes strong{font-size:1.125rem;font-weight:750;color:#fff}

/* Keep molecule diagrams proportional on narrow screens. */
.structure svg{display:block;width:min(100%,680px);height:auto;aspect-ratio:680/570;max-height:none}
@media(max-width:620px){
  .structure{min-height:0;padding:12px 8px}
  .structure svg{width:100%;height:auto;aspect-ratio:680/570}
}

/* Mobile width containment for the practice card. */
@media(max-width:620px){
  html,body{width:100%;max-width:100%;overflow-x:hidden}
  .practice,.bench,.exercise,.structure-frame,.structure{box-sizing:border-box;width:100%;max-width:100%;min-width:0}
  .bench{overflow:hidden}
  .exercise{padding:22px 12px}
  .structure-frame{overflow:hidden}
  .structure{padding:8px;overflow:hidden}
  .structure svg{display:block;width:100%!important;max-width:100%!important;height:auto!important;aspect-ratio:680/570;overflow:hidden}
  .structure-bar{min-width:0;padding:10px 12px}
  .structure-bar>span:last-child{display:none}
  .structure-caption{min-width:0;padding:10px 12px;align-items:flex-start}
  .structure-caption>span:last-child{min-width:0;overflow-wrap:anywhere}
}