:root{color-scheme:light;--ink:#193544;--muted:#586d7a;--paper:#edf3f5;--white:#fff;--line:#cfdee4;--water:#176d70;--rust:#9c5b3e;--steel:#667c8d;font-family:"PingFang SC","Microsoft YaHei","Noto Sans CJK SC",sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none}
*{box-sizing:border-box}body{margin:0;font-size:16px;line-height:1.75}a{color:var(--water);text-underline-offset:.25em}a:hover{text-decoration-thickness:2px}a:focus-visible,summary:focus-visible{outline:3px solid var(--water);outline-offset:5px}.skip-link{position:fixed;top:-100px;left:16px;z-index:2;padding:10px 18px;background:var(--white)}.skip-link:focus{top:12px}
.site-header,main,footer{width:min(1300px,calc(100% - 88px));margin-inline:auto}.site-header{display:flex;justify-content:space-between;gap:24px;padding-block:23px;border-bottom:1px solid var(--line);font-size:14px}.book-link{text-decoration:none;font-weight:600}.book-title{color:var(--muted)}
.intro{display:grid;grid-template-columns:minmax(0,1fr) 330px;gap:60px;align-items:center;padding:49px 0 39px}.eyebrow{margin:0 0 11px;color:var(--water);font-size:13px;font-weight:700;letter-spacing:.1em}h1{font-family:"Songti SC","STSong","SimSun",serif;font-size:clamp(35px,3.7vw,53px);font-weight:700;line-height:1.3;letter-spacing:.025em;margin:0 0 19px}.lead{max-width:650px;margin:0;font-size:16px;color:var(--muted)}.method-overview{display:inline-flex;gap:18px;align-items:center;margin-top:21px;font-size:14px;font-weight:600;text-decoration:none}.method-overview span{font-size:20px}.launch-panel{padding:24px 25px;background:#e2ecef;border-radius:12px;border:1px solid #ccdde1}.launch{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:15px 18px;background:var(--water);color:var(--white);border-radius:7px;font-size:17px;font-weight:700;text-decoration:none}.launch:hover{background:var(--ink)}.launch span{font-size:23px}.launch-panel p{margin:13px 0 0;font-size:13px;color:var(--muted)}.launch-panel .launch-note{font-size:11px;line-height:1.8}
.bridge-strip{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:25px}.bridge{--bridge-accent:var(--steel);background:var(--white);border:1px solid var(--line);border-radius:12px;overflow:hidden;box-shadow:0 4px 18px #19354405}.bridge-arch{--bridge-accent:var(--rust)}.bridge-stayed{--bridge-accent:var(--water)}.bridge-suspension{--bridge-accent:var(--ink)}.bridge-image{display:block;position:relative;aspect-ratio:1.94;overflow:hidden;background:#586b77;text-decoration:none}.bridge-image img{display:block;width:100%;height:100%;object-fit:cover;transition:transform .35s ease}.bridge-image:hover img{transform:scale(1.025)}.image-action{position:absolute;right:17px;bottom:15px;padding:4px 11px;border:1px solid #ffffff45;border-radius:20px;background:#153340d9;color:#fff;font-size:11px;letter-spacing:.02em}.bridge-copy{padding:22px 26px 0}.bridge-system{display:flex;align-items:center;gap:10px;margin:0 0 7px;font-size:14px;font-weight:700;color:var(--bridge-accent)}.bridge-system::before{content:"";width:22px;height:3px;background:var(--bridge-accent)}.bridge-system span{font-size:11px;font-weight:400;color:var(--muted);margin-left:auto}.bridge h2{font-family:"Songti SC","STSong","SimSun",serif;font-size:27px;line-height:1.45;margin:0 0 3px}.span{font-family:"Cascadia Code","Consolas",monospace;font-size:19px;line-height:1.5;margin:0 0 10px;color:var(--ink)}.span span{font-family:"PingFang SC","Microsoft YaHei",sans-serif;font-size:12px;color:var(--muted);white-space:nowrap}.bridge-copy>p:not(.bridge-system,.span,.observe){font-size:14px;color:var(--muted);margin:0 0 14px;min-height:1.75em}.observe{display:flex;gap:15px;align-items:baseline;padding-top:13px;margin:0 0 13px;border-top:1px solid var(--line);font-size:11px;color:var(--muted)}.observe strong{font-size:14px;color:var(--ink);font-weight:600}.method-preview{background:#f2f6f7;padding:10px 13px;border-radius:6px;margin-bottom:18px;min-height:78px}.method-preview p{display:flex;align-items:baseline;gap:12px;margin:0;font-size:12px;line-height:2;color:var(--ink)}.method-preview p span{flex-shrink:0;color:var(--muted);font-size:10px;letter-spacing:.06em}.bridge-actions{display:flex;justify-content:space-between;gap:20px;border-top:1px solid var(--line)}.bridge-actions a{display:flex;align-items:center;gap:16px;font-size:13px;font-weight:600;padding-block:14px;text-decoration:none;min-height:49px}.bridge-actions a:last-child{color:var(--muted);font-weight:400}.bridge-actions a:hover{color:var(--water)}.preview-caption{color:var(--muted);font-size:11px;margin:13px 0 0;line-height:1.9}
.use-guide{display:grid;grid-template-columns:1fr 2fr;gap:60px;border-top:1px solid var(--line);padding-block:36px;margin-top:36px}.guide-heading h2{font-family:"Songti SC","STSong","SimSun",serif;font-size:27px;line-height:1.6;margin:0}.guide-items{display:grid;grid-template-columns:1fr 1fr;column-gap:34px;row-gap:24px}.guide-items h3{font-size:15px;margin:0 0 6px}.guide-items p{font-size:13px;color:var(--muted);margin:0}.source-details{border-block:1px solid var(--line);margin-bottom:28px}.source-details summary{padding:17px 0;font-size:14px;font-weight:600;cursor:pointer}.source-content{max-width:970px;padding:0 0 16px;font-size:13px;color:var(--muted)}.source-content p:first-child{margin-top:0}.source-content ul{padding-left:22px}.source-content li{margin-block:10px}footer{display:flex;justify-content:space-between;gap:20px;color:var(--muted);font-size:12px;padding:0 0 max(28px,env(safe-area-inset-bottom))}
@media(max-width:1050px){.site-header,main,footer{width:calc(100% - 48px)}.intro{grid-template-columns:minmax(0,1fr) 285px;gap:32px}.launch-panel{padding:19px}.bridge-strip{gap:20px}.bridge-copy{padding:19px 20px 0}.bridge-copy>p:not(.bridge-system,.span,.observe){min-height:3.5em}.bridge-image{aspect-ratio:1.7}.use-guide{grid-template-columns:1fr;gap:25px}.guide-heading h2 br{display:none}.method-preview{min-height:96px}}
@media(max-width:660px){.site-header,main,footer{width:calc(100% - 32px)}.site-header{padding-block:17px;font-size:12px;gap:10px}.intro{grid-template-columns:1fr;gap:24px;padding:31px 0 25px}h1{font-size:36px}.lead{font-size:14px}.method-overview{font-size:12px;margin-top:14px}.launch-panel{padding:17px}.launch{font-size:16px}.launch-panel p br{display:none}.launch-panel .launch-note{margin-top:8px}.bridge-strip{grid-template-columns:1fr;gap:20px}.bridge-image{aspect-ratio:1.75}.bridge-copy{padding:18px 19px 0}.bridge h2{font-size:26px}.span{font-size:18px}.bridge-copy>p:not(.bridge-system,.span,.observe){font-size:13px;min-height:0}.method-preview{min-height:0}.method-preview p{font-size:11px;gap:10px}.bridge-actions{gap:10px}.bridge-actions a{font-size:12px;gap:10px}.observe strong{font-size:13px}.use-guide{padding-block:28px;margin-top:27px}.guide-items{grid-template-columns:1fr;gap:21px}.guide-heading h2{font-size:24px}footer{flex-direction:column;gap:7px}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{scroll-behavior:auto!important;transition:none!important}}
.topic-jump{display:flex;align-items:center;gap:15px;width:fit-content;margin-top:12px;font-size:14px;font-weight:600;text-decoration:none}.topic-jump span{font-size:18px}.composite-topic{display:grid;grid-template-columns:minmax(0,1.08fr) minmax(0,1fr);align-items:center;gap:34px;margin-top:36px;padding:28px;border:1px solid #b9d6d3;border-radius:12px;background:#f7fbfa;scroll-margin-top:24px}.composite-preview{position:relative;display:block;min-width:0;overflow:hidden;border:1px solid var(--line);border-radius:8px;background:#e8eef2}.composite-preview img{display:block;width:100%;height:auto;aspect-ratio:16/9;object-fit:contain}.composite-copy h2{font-family:"Songti SC","STSong","SimSun",serif;font-size:28px;line-height:1.5;margin:0 0 12px}.composite-copy>p:not(.eyebrow,.composite-scope){font-size:14px;color:var(--muted);margin:0 0 16px}.composite-features{display:flex;flex-wrap:wrap;gap:7px;list-style:none;margin:0 0 18px;padding:0}.composite-features li{padding:4px 9px;border:1px solid #cee0dd;border-radius:5px;font-size:11px;background:#fff;color:var(--water)}.composite-actions{display:flex;flex-wrap:wrap;gap:7px 20px}.composite-actions a{display:inline-flex;align-items:center;gap:10px;min-height:44px;font-size:13px;font-weight:600;text-decoration:none}.composite-actions a:first-child{padding:8px 13px;border-radius:6px;background:var(--water);color:white}.composite-actions a:first-child:hover{background:var(--ink)}.composite-copy .composite-scope{margin:15px 0 0;font-size:11px;line-height:1.85;color:var(--muted)}
@media(max-width:1050px){.composite-topic{grid-template-columns:1fr;gap:24px;padding:24px}.composite-preview{max-width:760px;width:100%;margin-inline:auto}.composite-copy h2 br{display:none}}
@media(max-width:660px){.topic-jump{font-size:12px;margin-top:10px}.composite-topic{margin-top:27px;padding:16px;gap:20px}.composite-copy h2{font-size:24px}.composite-copy>p:not(.eyebrow,.composite-scope){font-size:13px}.composite-actions{flex-direction:column;align-items:flex-start;gap:4px}.composite-actions a{font-size:12px}.composite-features li{font-size:10px}.composite-copy .composite-scope{margin-top:10px}}