:root{--paper:#faf7ef;--ink:#253a30;--muted:#626d62;--green:#245c48;--soft:#e5eddf;--line:#d5d9cb;--orange:#b9522d;--white:#fffefb;--radius:12px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-family:"PingFang SC","Microsoft YaHei",system-ui,sans-serif;font-size:16px;line-height:1.6}button,input{font:inherit}button,a,input{ -webkit-tap-highlight-color:transparent}button{cursor:pointer}a{color:inherit;text-decoration:none}button{border:0}button:focus-visible,a:focus-visible,input:focus-visible,video:focus-visible{outline:3px solid var(--orange);outline-offset:4px}button:disabled{cursor:default;opacity:.65}[hidden]{display:none!important}header,main,footer{max-width:1280px;margin:auto;padding-left:48px;padding-right:48px}header{height:112px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid 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video{object-fit:contain}.question-overlay{position:absolute;inset:0;display:grid;place-items:center;background:rgba(18,35,25,.76);padding:16px;overflow:auto}.question-panel{width:min(100%,530px);background:var(--paper);padding:24px;border-radius:12px}.question-panel .eyebrow{margin-bottom:8px;font-size:11px}.question-panel h2{font-size:23px;margin-bottom:16px}.answers{display:grid;gap:8px}.answers button{text-align:left;background:var(--white);padding:12px 16px;border:1px solid var(--line);border-radius:6px;min-height:44px;color:var(--ink)}.answers button:hover{border-color:var(--green);background:var(--soft)}.answers button.correct{border-color:var(--green);background:var(--soft)}.answers button.wrong{border-color:var(--orange)}#feedback{min-height:24px;font-size:14px;margin:12px 0;color:var(--green)}.question-actions{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap}.play-tools{display:flex;gap:8px;align-items:center;flex-wrap:wrap;padding:16px 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