/* RUDO(TM) Learning Hub · design tokens and base. Single source for every page.
   Light is the only default. Dark exists solely as an explicit user choice (data-theme="dark"),
   never from the operating-system preference. Colours from the m681 visual contract (2026-11-03);
   bird colours live only in the canonical mascot files and are never restated here. */
@font-face{font-family:'Inter';font-style:normal;font-weight:100 900;font-display:swap;src:url(/assets/fonts/inter-latin-wght-normal.woff2) format('woff2');unicode-range:U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}
@font-face{font-family:'Inter';font-style:normal;font-weight:100 900;font-display:swap;src:url(/assets/fonts/inter-latin-ext-wght-normal.woff2) format('woff2');unicode-range:U+0100-02AF,U+0304,U+0308,U+0329,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF}
@font-face{font-family:'Instrument Serif';font-style:normal;font-weight:400;font-display:swap;src:url(/assets/fonts/instrument-serif-latin-400-normal.woff2) format('woff2')}
@font-face{font-family:'Instrument Serif';font-style:italic;font-weight:400;font-display:swap;src:url(/assets/fonts/instrument-serif-latin-400-italic.woff2) format('woff2')}
:root{
  /* semantic tokens */
  --page:#F5F8FB; --surface:#FFFFFF; --ink:#19324B; --muted:#526778;
  --primary:#0E6B63; --primary-hover:#09564F; --primary-tint:#E8F4F0; --on-primary:#FFFFFF;
  --accent:#E8B05B; --on-accent:#19324B;
  --line:#DCE5EB; --control:#6D8698; --focus:#1A6ED8;
  --warn-tint:#FFF5DF; --warn-ink:#744600; --err-tint:#FFF1EF; --err-ink:#B33B36;
  /* aliases so existing page CSS and inline styles restyle without per-page edits */
  --paper:var(--page); --paper-cream:var(--page); --paper-cool:var(--surface); --card:var(--surface);
  --slate:var(--muted); --slate-2:var(--muted);
  --navy:var(--primary); --navy-deep:var(--primary-hover); --on-navy:var(--on-primary); --lh-navy:var(--ink);
  --gold:var(--accent); --gold-deep:var(--primary); --gold-soft:var(--warn-tint);
  --moss-100:var(--primary-tint); --moss-300:#BFDDD6; --moss-500:#5E9F94; --moss-700:var(--primary); --moss-900:var(--ink);
  --ok:var(--primary); --warn:var(--warn-ink); --bad:var(--err-ink); --info:#1A5FB4; --sea:var(--primary);
  --radius:16px; --radius-sm:10px; --shadow:0 1px 2px rgba(25,50,75,.05),0 8px 28px rgba(25,50,75,.05);
  --font-body:'Inter','PingFang SC','Noto Sans SC','Microsoft YaHei',system-ui,-apple-system,'Segoe UI',sans-serif;
  --font-display:'Instrument Serif','Noto Serif SC','Source Han Serif SC','Songti SC','STSong',Georgia,serif;
  --font-mono:ui-monospace,SFMono-Regular,'JetBrains Mono',Menlo,Consolas,monospace;
  --maxw:1200px; --gutter:20px;
  color-scheme:light;
}
:root[data-theme="dark"]{
  --page:#0F1B26; --surface:#162534; --ink:#E8F0F5; --muted:#A9BBC8;
  --primary:#5CCBBC; --primary-hover:#86DDD1; --primary-tint:#17363A; --on-primary:#06201D;
  --line:#2A3D4E; --control:#7A93A4; --focus:#7DB3FF;
  --warn-tint:#3A2C10; --warn-ink:#F2CF8E; --err-tint:#3D1E1C; --err-ink:#F5A9A3; --info:#8DB8E6;
  --moss-300:#2A4F52; --moss-500:#5CCBBC; --shadow:0 1px 2px rgba(0,0,0,.3);
  color-scheme:dark;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-padding-top:88px}
body{margin:0;background:var(--page);color:var(--ink);font:16px/1.65 var(--font-body);-webkit-font-smoothing:antialiased;font-feature-settings:'cv11','ss03'}
a{color:var(--primary);text-underline-offset:3px;text-decoration-thickness:1px}
a:hover{color:var(--primary-hover)}
h1,h2,h3{color:var(--ink);margin:.2em 0 .4em;text-wrap:balance}
h1{font:400 clamp(2.125rem,5vw,3.5rem)/1.12 var(--font-display);letter-spacing:-.005em}
h2{font:400 clamp(1.625rem,3vw,2.125rem)/1.18 var(--font-display)}
h3{font:600 1.125rem/1.35 var(--font-body)}
:lang(zh-CN) h1,:lang(zh-CN) h2{font-weight:600;letter-spacing:0}
:lang(zh-CN) h1{line-height:1.22}
code,.mono{font-family:var(--font-mono)}
.num,.mono,table{font-variant-numeric:tabular-nums}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 var(--gutter)}
@media(min-width:760px){:root{--gutter:32px}}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);min-width:0}
@media(min-width:760px){.card{padding:24px}}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:.4em;min-height:44px;border:1px solid var(--control);background:var(--surface);color:var(--ink);
  border-radius:10px;padding:.55em 1.1em;font:600 15px/1.25 var(--font-body);cursor:pointer;text-decoration:none;transition:background-color .12s,border-color .12s,color .12s}
.btn:hover{border-color:var(--primary);color:var(--primary)}
.btn-primary,a.btn-primary,a.btn-primary:visited{background:var(--primary);border-color:var(--primary);color:var(--on-primary)}
.btn-primary:hover,a.btn-primary:hover{background:var(--primary-hover);border-color:var(--primary-hover);color:var(--on-primary)}
.btn:disabled{opacity:.6;cursor:not-allowed}
a.btn{color:var(--ink)} a.btn:hover{color:var(--primary)}
a.btn-primary,a.btn-primary:visited,a.btn-primary:hover{color:var(--on-primary)}
.pill{display:inline-block;font:600 12.5px/1.5 var(--font-body);letter-spacing:.02em;padding:.15em .65em;border-radius:999px;border:1px solid var(--line);color:var(--muted);background:var(--surface);white-space:nowrap}
.pill.ok{color:var(--primary);border-color:transparent;background:var(--primary-tint)}
.pill.warn{color:var(--warn-ink);border-color:transparent;background:var(--warn-tint)}
.pill.bad{color:var(--err-ink);border-color:transparent;background:var(--err-tint)}
.muted{color:var(--muted)} .small{font-size:.875rem}
.grid{display:grid;gap:16px} .grid>*{min-width:0}
@media(min-width:760px){.grid{gap:20px}.grid.c2{grid-template-columns:1fr 1fr}.grid.c3{grid-template-columns:repeat(3,1fr)}}
input,select,textarea{font:inherit;color:var(--ink);background:var(--surface);border:1px solid var(--control);border-radius:var(--radius-sm);padding:.55em .7em;max-width:100%}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px;border-radius:4px}
table{border-collapse:collapse;width:100%} th,td{text-align:left;padding:.55em .7em;border-bottom:1px solid var(--line)} th{font-size:.8125rem;font-weight:600;color:var(--muted)}
img,svg{max-width:100%}

/* site chrome */
.site-head{position:sticky;top:0;z-index:20;background:var(--surface);border-bottom:1px solid var(--line)}
.head-row{display:flex;align-items:center;gap:12px;min-height:68px}
.logo{display:flex;align-items:center;flex:0 0 auto;padding:4px 0;color:var(--ink,#19324B);text-decoration:none}
.logo img{height:44px;width:auto;display:block}
@media(min-width:1040px){.logo img{height:52px}}
@media(max-width:359px){.head-row{gap:8px}.head-tools{gap:0}.logo img{height:36px}}
/* The lockup has a navy wordmark and no dark version: on dark it sits on a white plate, unaltered. */
:root[data-theme="dark"] .logo{background:#fff;border-radius:8px;padding:4px 8px}
@media(max-width:479px){:root[data-theme="dark"] .logo{padding:2px 3px}}
@media(max-width:359px){:root[data-theme="dark"] .logo{padding:2px}:root[data-theme="dark"] .logo img{height:32px}}
.main-nav{display:none;gap:2px}
.main-nav a{color:var(--ink);text-decoration:none;font-weight:500;font-size:.9375rem;padding:.5em .75em;border-radius:8px;white-space:nowrap}
.main-nav a:hover{background:var(--primary-tint);color:var(--primary-hover)}
.main-nav a[aria-current="page"]{color:var(--primary);box-shadow:inset 0 -2px 0 var(--primary);border-radius:8px 8px 0 0}
.head-tools{display:flex;align-items:center;gap:6px;margin-left:auto}
.tool{display:inline-flex;align-items:center;justify-content:center;min-width:44px;min-height:44px;background:none;border:0;border-radius:8px;color:var(--ink);font:500 14px var(--font-body);cursor:pointer;padding:0 8px}
.tool:hover{background:var(--primary-tint);color:var(--primary-hover)}
.tool svg{width:20px;height:20px;display:block}
.head-cta{display:none}
#nav-toggle{display:inline-flex}
.nav-panel{border-top:1px solid var(--line);padding:8px var(--gutter) 16px;background:var(--surface)}
.nav-panel a:not(.btn){display:flex;align-items:center;min-height:44px;color:var(--ink);text-decoration:none;font-weight:500}
.nav-panel a[aria-current="page"]{color:var(--primary);font-weight:600}
.nav-panel .btn{width:100%;margin-top:8px}
@media(min-width:1040px){.main-nav{display:flex;margin-left:16px}.head-cta{display:inline-flex}#nav-toggle{display:none}.nav-panel{display:none}}
@media(min-width:480px) and (max-width:1039px){.head-cta{display:inline-flex}.nav-panel .btn{display:none}}
.sub-nav{background:var(--primary-tint);border-bottom:1px solid var(--line)}
.sub-nav .wrap{display:flex;align-items:center;gap:4px 18px;min-height:44px;overflow-x:auto;scrollbar-width:thin}
.sub-nav .title{font-weight:600;font-size:.875rem;color:var(--ink);white-space:nowrap;margin-right:6px}
.sub-nav a{color:var(--ink);text-decoration:none;font-size:.875rem;white-space:nowrap;display:inline-flex;align-items:center;min-height:44px}
.sub-nav a:hover{color:var(--primary)}
.sub-nav a[aria-current="page"]{color:var(--primary);font-weight:600;box-shadow:inset 0 -2px 0 var(--primary)}
.site-foot{margin-top:72px;padding:48px 0 40px;background:var(--surface);border-top:1px solid var(--line);color:var(--muted);font-size:.875rem}
.foot-grid{display:grid;gap:28px}
@media(min-width:760px){.foot-grid{grid-template-columns:1.5fr 1fr 1fr 1fr}}
.foot-grid h2{font:600 .8125rem/1.4 var(--font-body);color:var(--ink);margin:0 0 8px}
.foot-grid ul{list-style:none;margin:0;padding:0}
.foot-grid li a{display:inline-flex;align-items:center;min-height:32px;color:var(--muted);text-decoration:none}
.foot-grid li a:hover{color:var(--primary);text-decoration:underline}
.foot-mark{display:flex;gap:12px;align-items:flex-start}
.foot-mark img{flex:0 0 auto;width:36px;height:auto}
.foot-mark strong{color:var(--ink)}
.disclaimer{font-size:.8125rem;color:var(--muted);border-top:1px solid var(--line);margin-top:28px;padding-top:16px;max-width:none}
/* links inside running text stay underlined, never colour-only */
p a:not(.btn),li a:not(.btn),td a:not(.btn),dd a:not(.btn),.crumbs a,nav[aria-label*="readcrumb"] a,.breadcrumb a{text-decoration:underline}
.foot-grid li a:not(:hover){text-decoration:none}
@media (prefers-reduced-motion:reduce){*,*::before,*::after{animation-duration:.001ms!important;animation-iteration-count:1!important;transition-duration:.001ms!important;scroll-behavior:auto!important}}