:root{--base:#f6fafc;--white:#fff;--ice:#eaf6fa;--ice2:#edf4f8;--cyan:#25c8d1;--sky:#25b6e8;--blue:#1787db;--navy:#174b78;--ink:#183a56;--text:#31485d;--muted:#687d8e;--line:#dce9f0;--footer:#123653;--shell:1180px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:30px}body{margin:0;background:var(--base);color:var(--text);font:16px/1.8 Arial,"PingFang SC","Microsoft YaHei",sans-serif;overflow-x:hidden}a{color:var(--navy);text-decoration-thickness:1px;text-underline-offset:4px}a:hover{color:var(--blue)}button{font:inherit}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid var(--cyan);outline-offset:3px}.shell{width:min(calc(100% - 56px),var(--shell));margin-inline:auto}.site-header{background:#fff;position:relative;z-index:30;border-bottom:1px solid var(--line)}.topbar{height:72px;display:flex;align-items:center;gap:22px}.brand{flex:0 0 auto;display:inline-flex;align-items:center;max-width:240px;text-decoration:none}.brand 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