/* Shared navigation and page furniture for 人工智能的来路; long-form reading keeps its preferences. */
:root{--site-display:"Avenir Next","PingFang SC","Microsoft YaHei",sans-serif;--site-action:#273f53;--site-copper:#d6b997}
body .topbar,body.spatial-home .topbar,body.learning-surface .topbar{box-sizing:border-box;width:min(960px,calc(100% - 28px));height:62px;min-height:62px;margin:10px auto 0;top:8px;padding:7px 18px;gap:26px;border:1px solid #cdd8e3;border-radius:9px;background:#f6f9fcf2;box-shadow:0 1px 0 #fff8;backdrop-filter:blur(16px)}
body .brand,body.spatial-home .brand,body.learning-surface .brand{font-family:var(--site-display);font-size:19px;letter-spacing:.07em;gap:10px;color:#293946;font-weight:600}
body .brand-mark,body.spatial-home .brand-mark,body.learning-surface .brand-mark{width:35px;height:35px;font-size:27px;line-height:35px;color:#455561;background:#f8fafc;border-color:#a8b6c2;box-shadow:inset 0 0 0 4px #edf2f6}
body .brand small,body.spatial-home .brand small,body.learning-surface .brand small{font-family:var(--site-display);font-size:9px;line-height:1.5;letter-spacing:.025em;font-weight:400;color:#788d9b;margin-top:1px}
body .topnav{gap:12px}
body .topnav a,body.spatial-home .topnav a,body.learning-surface .topnav a{font:13px/1.5 var(--site-display);padding:8px 11px;border-radius:5px;color:#5c7384;transition:background-color .18s,color .18s}
body .topnav a:is(:hover,:focus-visible),body.spatial-home .topnav a:is(:hover,:focus-visible),body.learning-surface .topnav a:is(:hover,:focus-visible){background:#e1e9ee;color:#233f51}
body .topnav a.active,body.spatial-home .topnav a.active,body.learning-surface .topnav a.active{background:#e5ebee;color:#243d4e}
body .topnav a[data-nav=courses],body .topnav a[data-nav=about],body .global-appearance{display:none}
body .search-trigger,body.spatial-home .search-trigger,body.learning-surface .search-trigger{min-width:0;padding:8px;background:transparent;border:0;color:#5c7384}
body .search-trigger span{font-size:0;display:inline}body .search-trigger span::after{content:'搜索';font:12px/1 var(--site-display)}body .search-trigger kbd{display:none}
body .search-trigger:hover{background:#e1e9ee;border-radius:5px}
.learning-surface{--ink:#263c49;--text:#465866;--muted:#748793;--line:#ccd7de;--white:#fbfcfd;--paper:#f1f4f7;--soft:#e7edf1;--accent:#9e815e;font-family:var(--site-display)}
.learning-surface .page-header h1{font-family:var(--site-display);font-size:clamp(34px,4vw,48px);font-weight:500;line-height:1.3;color:#283e4c;letter-spacing:-.035em}
.learning-surface .page-header .eyebrow{font-size:10px;letter-spacing:.16em;color:#9a7d58}
.learning-surface .page-header>p:not(.eyebrow){font-size:14px;line-height:1.9;color:#70838f;max-width:760px}
.learning-surface .button,.learning-surface .chapter-gateway-start{font:13px/1.5 var(--site-display);background:var(--site-action);border:1px solid var(--site-action);color:#f7fafc;border-radius:5px;padding:11px 20px;box-shadow:none;transition:background-color .18s}
.learning-surface .button:hover,.learning-surface .chapter-gateway-start:hover{background:#3a596e}
.learning-surface .button.secondary{background:transparent;color:#344d5e;border-color:#abbfcb}
.learning-surface .button.secondary:hover{background:#e2eaef}
.learning-surface .small-button{font:12px/1.5 var(--site-display);border:1px solid #b9c8d2;border-radius:5px;background:#f9fbfc;color:#415d70;padding:9px 13px}
.learning-surface .small-button:hover{background:#e2eaef}
.learning-surface .notes-overview{gap:48px;padding:14px 0 25px}
.learning-surface .notes-overview strong{font:400 36px/1.3 var(--site-display);color:#334c5d}
.learning-surface .notes-overview span{font-size:12px;color:#70838f}
.learning-surface .note-card{padding:26px 22px;border:1px solid #d1dce3;border-radius:6px;background:#f7fafc;margin:16px 0;transition:background-color .18s}
.learning-surface .note-card:hover{background:#fff}
.learning-surface .note-card h3{font:500 19px/1.6 var(--site-display);color:#2b4556}
.learning-surface .note-card p{font-size:14px;line-height:1.9;color:#667b89}
.learning-surface .empty-state{padding:36px 0 56px}
.learning-surface .empty-state h2,.learning-surface .about-prose h2{font:500 25px/1.5 var(--site-display);letter-spacing:-.02em;color:#314b5c}
.learning-surface .about-prose{font-size:15px;line-height:1.95;color:#546b79}
.learning-surface .about-prose h2{padding-top:22px;border-top:1px solid #d1dce3}
body .site-footer{width:100%;max-width:none;box-sizing:border-box}
html[data-reading-theme=night] body.spatial-reading .topbar{background:#202b31f2;border-color:#40515c}
html[data-reading-theme=night] body.spatial-reading .brand{color:#e2e9eb}
html[data-reading-theme=night] body.spatial-reading .brand small{color:#9bb0bc}
html[data-reading-theme=night] body.spatial-reading .topnav a,html[data-reading-theme=night] body.spatial-reading .search-trigger{color:#b6c7cf}
html[data-reading-theme=night] body.spatial-reading .topnav a:is(.active,:hover){background:#35454f;color:#f0f5f7}
@media(max-width:760px){
 body .topbar,body.spatial-home .topbar,body.learning-surface .topbar{width:calc(100% - 20px);height:60px;min-height:60px;top:5px;padding:7px 12px;gap:9px}
 body .brand,body.spatial-home .brand,body.learning-surface .brand{font-size:17px;gap:8px}
 body .brand small,body.spatial-home .brand small,body.learning-surface .brand small{font-size:8px;letter-spacing:0}
 body .topnav{gap:2px;margin-left:auto}
 body .topnav a,body.spatial-home .topnav a,body.learning-surface .topnav a{font-size:12px;padding:7px 6px}
 .learning-surface .note-card{padding:20px 15px}.learning-surface .note-card h3{font-size:17px}
}
@media(max-width:380px){body .brand-mark,body.spatial-home .brand-mark,body.learning-surface .brand-mark{width:29px;height:29px;font-size:23px;line-height:29px}body .topnav a,body.spatial-home .topnav a,body.learning-surface .topnav a{padding-inline:4px;font-size:11px}}
@media(prefers-reduced-motion:reduce){body .topnav a,.learning-surface .button,.learning-surface .note-card{transition:none}}
@media print{body .topbar,body.spatial-home .topbar,body.learning-surface .topbar{display:none}}
body.spatial-home .topnav,body.learning-surface .topnav{gap:12px}
html[data-reading-theme=white] body.spatial-reading{--ink:#263c49;--text:#465866;--muted:#748793;--line:#ccd7de;--white:#fbfcfd;--paper:#f4f7f9;--soft:#e7edf1;--accent:#9e815e;background-image:none}
@media(max-width:760px){body.spatial-home .topnav,body.learning-surface .topnav{gap:2px}}
@media(max-width:760px){
 body .brand,body.spatial-home .brand,body.learning-surface .brand{font-size:15px;letter-spacing:.015em;gap:7px}
 body .topbar,body.spatial-home .topbar,body.learning-surface .topbar{padding-inline:10px;gap:7px}
}
@media(max-width:380px){
 body .brand,body.spatial-home .brand,body.learning-surface .brand{font-size:14px;gap:5px}
 body .brand small,body.spatial-home .brand small,body.learning-surface .brand small{font-size:7px}
 body .topnav a,body.spatial-home .topnav a,body.learning-surface .topnav a{padding-inline:3px;font-size:11px}
}
body .brand-mark.brand-logo,body.spatial-home .brand-mark.brand-logo,body.learning-surface .brand-mark.brand-logo{display:block;width:42px;height:42px;flex:0 0 42px;border:0;border-radius:0;background:transparent;box-shadow:none;line-height:1}
.brand-logo img{display:block;width:100%;height:100%;object-fit:contain}
html[data-reading-theme=night] body.spatial-reading .brand-mark.brand-logo{background:#f1f4f7;border-radius:7px}
@media(max-width:760px){body .brand-mark.brand-logo,body.spatial-home .brand-mark.brand-logo,body.learning-surface .brand-mark.brand-logo{width:36px;height:36px;flex-basis:36px}}
.hero-scroll-hint{display:flex;align-items:center;justify-content:center;gap:9px;margin:16px auto 0;color:#7b8f9c;font:13px/1.8 var(--site-display);letter-spacing:.025em}
.hero-scroll-hint svg{width:16px;height:16px;stroke:#aa906d;stroke-width:1.3}
@media(max-width:760px){.hero-scroll-hint{font-size:12px;margin-top:13px}}
html[data-atlas-surface=dark]{background:#121719}
html[data-atlas-surface=dark] body.spatial-home.atlas-dark-surface{background:#121719;transition:none}