:root{--paper:#fff;--wash:#f3f6fc;--ink:#152644;--muted:#526178;--line:#dce3ee;--blue:#245ddd;--pale:#eaf0ff;--error:#9b2727}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.7 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC",sans-serif}header,main,footer{max-width:1080px;margin:auto}header{display:flex;align-items:center;justify-content:space-between;padding:28px 32px;border-bottom:1px solid var(--line)}a{color:var(--blue);text-underline-offset:4px}.brand{color:var(--ink);text-decoration:none;font-weight:650;letter-spacing:.02em}.brand span{display:inline-block;color:var(--blue);font:34px Georgia,serif;margin-right:8px;vertical-align:middle}main{padding:56px 32px;display:grid;grid-template-columns:1.2fr 1fr;gap:56px 60px}.eyebrow{font-size:13px;color:var(--muted);letter-spacing:.1em;margin:0}h1{font-size:40px;line-height:1.4;letter-spacing:-.03em;margin:14px 0 22px;font-weight:650}h2{font-size:21px;line-height:1.4;margin:0 0 22px}p{margin:12px 0}.lead{max-width:360px;color:var(--muted)}.specimen{border-left:3px solid var(--blue);padding:14px 20px;margin-top:34px}.math{display:block;font:38px/1.6 Georgia,"Songti SC",serif}.specimen code{font:13px/1.8 ui-monospace,SFMono-Regular,monospace;word-break:break-all;color:var(--muted)}.caption{font-size:13px;color:var(--muted)}.download{display:inline-flex;gap:28px;align-items:center;margin-top:20px;text-decoration:none;font-weight:600}.purchase{padding:28px;background:var(--wash);border-radius:16px;align-self:start}.price{font-size:42px;line-height:1.2;font-weight:650;letter-spacing:-.04em;margin:16px 0}.price small{font-size:15px;font-weight:400;letter-spacing:0;margin-left:8px}label{display:block;font-size:14px;margin:14px 0 7px}input:not([type=checkbox]),select{font:inherit;width:100%;padding:10px 12px;background:white;color:var(--ink);border:1px solid var(--line);border-radius:7px;min-width:0}input[type=password]{font-family:ui-monospace,SFMono-Regular,monospace;font-size:14px}.check{display:flex;gap:10px;align-items:flex-start;font-size:13px;line-height:1.65;margin:20px 0}.check input{margin-top:4px;flex-shrink:0;accent-color:var(--blue)}button{font:inherit;line-height:1.4;font-weight:600;padding:12px 18px;border:1px solid var(--blue);background:var(--blue);color:white;border-radius:7px;cursor:pointer}form>button,.purchase button{width:100%;margin-top:10px}.secondary{background:transparent;color:var(--blue)}button:disabled{opacity:.45;cursor:not-allowed}a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #8baeff;outline-offset:3px}.order-section,.account,.notes{grid-column:1/-1;border-top:1px solid var(--line);padding-top:30px}.section-title{display:flex;align-items:center;justify-content:space-between;gap:20px}.section-title h2{margin:0}.account{display:grid;grid-template-columns:1fr 1fr;gap:60px}.notes p{color:var(--muted);font-size:14px}.actions{display:flex;gap:12px;margin-top:14px}.error{color:var(--error)}footer{padding:0 32px 40px;font-size:13px;color:var(--muted)}[hidden]{display:none!important}@media(max-width:760px){header{padding:18px 22px}main{padding:36px 22px;grid-template-columns:1fr;gap:36px}.account{grid-template-columns:1fr;gap:30px}h1{font-size:33px}.purchase{padding:24px}.section-title{align-items:flex-start;flex-direction:column}.actions{flex-wrap:wrap}.math{font-size:32px}footer{padding:0 22px 30px}}@media(prefers-reduced-motion:no-preference){button,a{transition:opacity .15s}button:hover:not(:disabled),a:hover{opacity:.83}}

.guide{grid-column:1/-1;border-top:1px solid var(--line);padding-top:30px}.guide ol{padding-left:24px}.guide li{margin:10px 0}.guide h2:not(:first-child){margin-top:32px}.guide details{border-top:1px solid var(--line);padding:15px 0}.guide summary{cursor:pointer;font-weight:600}.guide details p{color:var(--muted);font-size:14px}.sale-state{color:var(--muted);font-size:14px}