/* ============================================================
   site.css — 四季主页 共享外壳
   1. reset  2. 变量  3. 排版  4. 通用组件  5. 页头  6. 页脚
   7. 响应式  8. 动效降级
   ============================================================ */

/* 1. reset */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,ul,ol,li,figure,blockquote,dl,dd{margin:0}
ul,ol{padding:0;list-style:none}
img,svg,video,picture{display:block;max-width:100%}
button{font:inherit;color:inherit;background:none;border:0;padding:0;cursor:pointer}
a{color:inherit;text-decoration:none}
main{display:block}

/* 2. 变量 */
:root{
  --paper:#F7F6F2;
  --ink:#1C1B19;
  --forest:#2F4231;
  --spring:#7FA96B;
  --summer:#4E8CA8;
  --autumn:#C97A45;
  --winter:#9AA3A8;
  --beige:#E8E2D6;
  --pencil:#6B6A66;
  --highlight:#E4D06A;
  --line:rgba(28,27,25,.14);
  --line-strong:rgba(28,27,25,.30);
  --on-dark:rgba(247,246,242,.78);
  --on-dark-dim:rgba(247,246,242,.52);
  --on-dark-line:rgba(247,246,242,.20);
  --font-display:"Source Han Sans SC Heavy","Noto Sans SC","PingFang SC","Microsoft YaHei",sans-serif;
  --font-body:"Inter","Noto Sans SC","PingFang SC",system-ui,"Microsoft YaHei",sans-serif;
  --font-mono:"IBM Plex Mono","JetBrains Mono",ui-monospace,SFMono-Regular,"Courier New",monospace;
  --r:2px;
  --pad:clamp(20px,5vw,64px);
  --shell-max:1240px;
  --header-h:78px;
  --gap:clamp(20px,3vw,36px);
  --ease:cubic-bezier(.2,.7,.3,1);
}

/* 3. 排版 */
body{
  background-color:var(--paper);
  color:var(--ink);
  font-family:var(--font-body);
  font-size:17px;
  line-height:1.85;
  letter-spacing:.01em;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
h1,h2,h3,h4{font-family:var(--font-display);font-weight:900;line-height:1.15;letter-spacing:-.01em}
h1{font-size:clamp(2.4rem,6.4vw,5.6rem)}
h2{font-size:clamp(1.6rem,3.4vw,2.8rem)}
h3{font-size:clamp(1.15rem,2vw,1.55rem);line-height:1.3}
h4{font-size:1.05rem;line-height:1.4;letter-spacing:0}
p{max-width:none}
strong{font-weight:700}
.mono{font-family:var(--font-mono);letter-spacing:.08em}
.index-code{font-family:var(--font-mono);font-size:.75rem;letter-spacing:.08em;color:var(--pencil)}
.prose p{max-width:66ch;margin-bottom:1.4em;color:var(--ink)}
.prose p:last-child{margin-bottom:0}
:focus-visible{outline:2px solid var(--highlight);outline-offset:3px;border-radius:1px}
[id]{scroll-margin-top:calc(var(--header-h) + 24px)}
#main-content{scroll-margin-top:calc(var(--header-h) + 16px)}

/* 4. 通用组件 */
.shell{width:100%;max-width:var(--shell-max);margin-inline:auto;padding-inline:var(--pad)}

.skip-link{
  position:fixed;top:10px;left:10px;z-index:200;
  transform:translateY(-180%);
  background-color:var(--ink);color:var(--paper);
  padding:.7em 1.1em;border-radius:var(--r);
  font-family:var(--font-mono);font-size:.75rem;letter-spacing:.1em;
  transition:transform 200ms var(--ease);
}
.skip-link:focus,.skip-link:focus-visible{transform:translateY(0);outline:2px solid var(--highlight);outline-offset:2px}

.page-head{padding-top:calc(var(--header-h) + clamp(44px,7vw,88px));padding-bottom:clamp(28px,5vw,56px)}
.page-head__title{max-width:22ch}
.lede{margin-top:1.25rem;max-width:58ch;font-size:clamp(1rem,1.5vw,1.12rem);line-height:1.85;color:var(--pencil)}

.crumbs{display:flex;flex-wrap:wrap;align-items:center;gap:.55em;margin-bottom:1.5rem;font-family:var(--font-mono);font-size:.72rem;letter-spacing:.08em;color:var(--pencil)}
.crumbs li{display:inline-flex;align-items:center;gap:.55em}
.crumbs li+li::before{content:"/";color:var(--line-strong)}
.crumbs a{transition:color 200ms var(--ease)}
.crumbs a:hover{color:var(--ink);text-decoration:underline;text-underline-offset:3px;text-decoration-color:var(--autumn)}

.section{padding-block:clamp(56px,9vw,120px)}
.section__head{display:grid;gap:.85rem;padding-top:clamp(18px,3vw,30px);margin-bottom:clamp(26px,4vw,52px);border-top:1px solid var(--line-strong)}
.section__title{max-width:24ch}
.section__lede{max-width:56ch;color:var(--pencil);font-size:1rem}

.eyebrow{display:inline-flex;align-items:center;gap:.7em;font-family:var(--font-mono);font-size:.72rem;letter-spacing:.22em;text-transform:uppercase;color:var(--pencil)}
.eyebrow::before{content:"";width:26px;height:1px;background:currentColor;flex:none}

.vertical-note{
  writing-mode:vertical-rl;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.3em;
  color:var(--pencil);line-height:1;
  align-self:start;
}

.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.55em;
  padding:.85em 1.6em;border:1px solid var(--ink);border-radius:var(--r);
  font-family:var(--font-body);font-weight:600;font-size:1rem;line-height:1.2;letter-spacing:.02em;
  color:var(--ink);background-color:transparent;
  transition:transform 200ms var(--ease),background-color 200ms var(--ease),color 200ms var(--ease),border-color 200ms var(--ease);
}
.btn:hover{transform:translateY(-2px)}
.btn--primary{background-color:var(--autumn);border-color:var(--autumn);color:var(--paper);font-size:1.125rem}
.btn--primary:hover{background-color:var(--ink);border-color:var(--ink);color:var(--paper)}
.btn--ghost{color:var(--pencil);border-color:var(--line-strong)}
.btn--ghost:hover{color:var(--ink);border-color:var(--ink)}

.season--spring{--season:var(--spring)}
.season--summer{--season:var(--summer)}
.season--autumn{--season:var(--autumn)}
.season--winter{--season:var(--winter)}

.card{
  position:relative;display:block;
  background-color:var(--beige);
  border:1px solid var(--line-strong);border-radius:var(--r);
  padding:clamp(18px,2.6vw,30px);
  transition:transform 220ms var(--ease),border-color 220ms var(--ease),background-color 220ms var(--ease);
}
.card::after{
  content:"";position:absolute;inset:-1px;z-index:-1;
  border:1px solid var(--line);border-radius:var(--r);
  transform:translate(4px,4px);pointer-events:none;
  transition:transform 220ms var(--ease),border-color 220ms var(--ease);
}
.card:hover,.card:focus-within{transform:translateY(-4px);border-color:var(--highlight)}
.card:hover::after,.card:focus-within::after{transform:translate(6px,6px);border-color:var(--line-strong)}
.card__bar{height:3px;width:100%;background-color:var(--season,var(--winter));margin-bottom:1rem}
.card__index{display:block;font-family:var(--font-mono);font-size:.72rem;letter-spacing:.08em;color:var(--pencil)}
.card__title{margin-top:.5rem;font-family:var(--font-display);font-weight:900;font-size:clamp(1.1rem,1.8vw,1.4rem);line-height:1.3}

.tag{
  display:inline-flex;align-items:center;gap:.4em;
  padding:.3em .6em;border:1px solid var(--line-strong);border-radius:var(--r);
  font-family:var(--font-mono);font-size:.7rem;letter-spacing:.1em;
  color:var(--ink);background-color:transparent;
}
.tag--spring{background-color:rgba(127,169,107,.20);border-color:var(--spring)}
.tag--summer{background-color:rgba(78,140,168,.18);border-color:var(--summer)}
.tag--autumn{background-color:rgba(201,122,69,.18);border-color:var(--autumn)}
.tag--winter{background-color:rgba(154,163,168,.22);border-color:var(--winter)}

.grid{display:grid;gap:var(--gap);grid-template-columns:minmax(0,1fr)}
@media (min-width:720px){
  .grid--2{grid-template-columns:repeat(2,minmax(0,1fr))}
  .grid--3{grid-template-columns:repeat(2,minmax(0,1fr))}
}
@media (min-width:1024px){
  .grid--3{grid-template-columns:repeat(3,minmax(0,1fr))}
  .grid--split{grid-template-columns:minmax(0,7fr) minmax(0,5fr)}
  .grid--split-reverse{grid-template-columns:minmax(0,5fr) minmax(0,7fr)}
}

.archive-layout{display:grid;grid-template-columns:minmax(0,1fr);gap:var(--gap)}
.archive-layout__rail{display:flex;gap:1rem;align-items:center;padding-bottom:1rem;border-bottom:1px dashed var(--line)}
@media (min-width:1024px){
  .archive-layout{grid-template-columns:72px minmax(0,1fr);gap:clamp(20px,3vw,40px)}
  .archive-layout__rail{position:sticky;top:calc(var(--header-h) + 24px);align-self:start;display:block;padding-bottom:0;border-bottom:0}
}

.spy{font-family:var(--font-mono);font-size:.72rem;letter-spacing:.1em}
@media (min-width:1024px){
  .spy{position:sticky;top:calc(var(--header-h) + 28px)}
}
.spy__list{display:grid;gap:.85rem;padding-left:16px;border-left:1px solid var(--line)}
.spy__link{position:relative;display:block;padding-block:.15em;color:var(--pencil);transition:color 200ms var(--ease)}
.spy__link::before{
  content:"";position:absolute;left:-16px;top:50%;transform:translateY(-50%);
  width:2px;height:0;background-color:var(--autumn);
  transition:height 220ms var(--ease);
}
.spy__link:hover{color:var(--ink)}
.spy__link[aria-current="true"]{color:var(--ink);font-weight:700}
.spy__link[aria-current="true"]::before{height:1.4em}

.media-frame{position:relative;margin:0;display:grid;gap:.6rem}
.media-frame__box{
  position:relative;aspect-ratio:4/3;overflow:hidden;
  border:1px solid var(--line-strong);border-radius:var(--r);
  background-color:var(--beige);
}
.media-frame__box > img,
.media-frame__box > svg,
.media-frame__box > picture > img{width:100%;height:100%;object-fit:cover}
.media-frame--wide .media-frame__box{aspect-ratio:16/9}
.media-frame--tall .media-frame__box{aspect-ratio:3/4}
.media-frame--square .media-frame__box{aspect-ratio:1/1}
.media-frame__box--blank{
  background-image:repeating-linear-gradient(135deg,rgba(28,27,25,.06) 0 1px,transparent 1px 11px);
}
.media-frame__caption{font-family:var(--font-mono);font-size:.7rem;letter-spacing:.08em;color:var(--pencil)}

/* 5. 页头 */
.site-header{
  position:fixed;inset:0 0 auto 0;z-index:120;
  background-color:transparent;
  border-bottom:1px solid transparent;
  color:var(--ink);
  transition:background-color 260ms var(--ease),border-color 260ms var(--ease),color 260ms var(--ease);
}
.site-header[data-scrolled="true"]{background-color:var(--paper);border-bottom-color:var(--line-strong)}
.site-header__inner{display:flex;align-items:center;gap:clamp(14px,2.4vw,36px);min-height:var(--header-h)}

.brand{display:inline-flex;align-items:center;gap:.7rem;flex:none}
.brand__mark{width:36px;height:36px;flex:none}
.brand__mark svg{width:100%;height:100%;overflow:visible}
.brand__arc{fill:none;stroke-width:2.6;stroke-linecap:round}
.brand__arc--spring{stroke:var(--spring)}
.brand__arc--summer{stroke:var(--summer)}
.brand__arc--autumn{stroke:var(--autumn)}
.brand__arc--winter{stroke:var(--winter)}
.brand__core{fill:var(--ink);transition:fill 260ms var(--ease)}
.brand__text{display:grid;gap:1px}
.brand__name{font-family:var(--font-display);font-weight:900;font-size:1.2rem;line-height:1.1;letter-spacing:.03em}
.brand__meta{font-family:var(--font-mono);font-size:.62rem;line-height:1.3;letter-spacing:.18em;color:var(--pencil);transition:color 260ms var(--ease)}

.site-nav{flex:1 1 auto;display:flex;justify-content:center;min-width:0}
.site-nav__list{display:flex;align-items:center;gap:clamp(10px,1.7vw,26px)}
.site-nav__item{display:block}
.site-nav__link{
  position:relative;display:inline-block;padding-block:.45em;
  font-size:.95rem;font-weight:500;letter-spacing:.02em;
  color:inherit;opacity:.86;
  transition:opacity 200ms var(--ease),color 200ms var(--ease);
}
.site-nav__link::after{
  content:"";position:absolute;left:0;right:0;bottom:-2px;height:2px;
  background-color:var(--highlight);transform:scaleX(0);transform-origin:left;
  transition:transform 220ms var(--ease),background-color 220ms var(--ease);
}
.site-nav__link:hover{opacity:1}
.site-nav__link:hover::after,.site-nav__link:focus-visible::after{transform:scaleX(1)}
.site-nav__link[aria-current="page"]{opacity:1;font-weight:700}
.site-nav__link[aria-current="page"]::after{transform:scaleX(1);background-color:var(--autumn)}
.site-nav__extra{display:none}
.site-nav__extra-link{display:inline-block;font-family:var(--font-mono);font-size:.72rem;letter-spacing:.1em;color:var(--ink);text-decoration:underline;text-underline-offset:3px;text-decoration-color:var(--autumn)}
.site-nav__meta{font-family:var(--font-mono);font-size:.68rem;letter-spacing:.08em;color:var(--pencil)}

.site-header__actions{display:flex;align-items:center;gap:.75rem;flex:none}
.version-pill{
  display:inline-flex;align-items:center;gap:.5em;
  padding:.5em 1em;border:1px solid currentColor;border-radius:999px;
  font-family:var(--font-mono);font-size:.7rem;letter-spacing:.12em;white-space:nowrap;
  transition:background-color 200ms var(--ease),color 200ms var(--ease);
}
.version-pill:hover{background-color:var(--ink);color:var(--paper)}
.version-pill__dot{width:6px;height:6px;border-radius:50%;background-color:var(--autumn);flex:none;transition:background-color 200ms var(--ease)}
.version-pill:hover .version-pill__dot{background-color:var(--highlight)}

.nav-toggle{
  display:none;align-items:center;gap:.55em;
  padding:.5em .9em;border:1px solid currentColor;border-radius:999px;
  font-family:var(--font-mono);font-size:.7rem;letter-spacing:.14em;
  transition:background-color 200ms var(--ease),color 200ms var(--ease);
}
.nav-toggle__bars{display:inline-flex;flex-direction:column;gap:4px;width:16px;flex:none}
.nav-toggle__bars span{display:block;height:1.5px;width:100%;background-color:currentColor;transition:transform 220ms var(--ease),opacity 220ms var(--ease)}
.site-header[data-open="true"] .nav-toggle__bars span:first-child{transform:translateY(2.75px) rotate(45deg)}
.site-header[data-open="true"] .nav-toggle__bars span:last-child{transform:translateY(-2.75px) rotate(-45deg)}

/* 深色首屏页面：桌面端导航在未滚动时使用纸白字 */
@media (min-width:961px){
  body.has-dark-hero .site-header:not([data-scrolled="true"]){color:var(--paper)}
  body.has-dark-hero .site-header:not([data-scrolled="true"]) .brand__core{fill:var(--paper)}
  body.has-dark-hero .site-header:not([data-scrolled="true"]) .brand__meta{color:var(--on-dark-dim)}
  body.has-dark-hero .site-header:not([data-scrolled="true"]) .version-pill:hover{background-color:var(--paper);color:var(--forest)}
}

/* 6. 页脚 */
.site-footer{
  margin-top:clamp(64px,10vw,140px);
  background-color:var(--forest);color:var(--paper);
}
.archive-band{
  display:block;
  background-color:var(--beige);color:var(--ink);
  border-bottom:2px solid var(--forest);
  transition:background-color 220ms var(--ease);
}
.archive-band:hover,.archive-band:focus-visible{background-color:var(--highlight)}
.archive-band__inner{display:flex;align-items:center;flex-wrap:wrap;gap:.4rem clamp(10px,2vw,20px);padding-block:14px}
.archive-band__index{font-family:var(--font-mono);font-size:.72rem;letter-spacing:.1em;color:var(--pencil)}
.archive-band__title{font-family:var(--font-display);font-weight:900;font-size:1.05rem;line-height:1.2;letter-spacing:.02em}
.archive-band__note{font-family:var(--font-mono);font-size:.7rem;letter-spacing:.06em;color:var(--pencil)}
.archive-band__arrow{margin-left:auto;font-family:var(--font-mono);font-size:1rem;transition:transform 220ms var(--ease)}
.archive-band:hover .archive-band__arrow{transform:translateX(5px)}

.site-footer__main{
  display:grid;grid-template-columns:minmax(0,1fr);
  gap:clamp(28px,4vw,48px);
  padding-block:clamp(40px,6vw,72px);
}
.footer-brand__name{font-family:var(--font-display);font-weight:900;font-size:1.5rem;line-height:1.2;letter-spacing:.02em}
.footer-brand__text{margin-top:.7rem;max-width:34ch;font-size:.95rem;line-height:1.8;color:var(--on-dark)}
.footer-brand__mark{margin-top:1rem;font-family:var(--font-mono);font-size:.7rem;letter-spacing:.16em;color:var(--on-dark-dim)}
.footer-col{min-width:0}
.footer-col__title{
  margin-bottom:1rem;padding-bottom:.7rem;
  border-bottom:1px solid var(--on-dark-line);
  font-family:var(--font-mono);font-weight:400;font-size:.68rem;letter-spacing:.22em;
  color:var(--on-dark-dim);
}
.footer-list{display:grid;gap:.55rem;font-size:.95rem}
.footer-list a{display:inline-block;color:var(--on-dark);transition:color 200ms var(--ease)}
.footer-list a:hover,.footer-list a:focus-visible{
  color:var(--paper);
  text-decoration:underline;text-underline-offset:4px;text-decoration-thickness:1px;text-decoration-color:var(--highlight);
}
.footer-contact{display:grid;gap:.85rem;font-size:.9rem}
.footer-contact__item{display:grid;gap:2px}
.footer-contact__label{font-family:var(--font-mono);font-size:.62rem;letter-spacing:.18em;color:var(--on-dark-dim)}
.footer-contact__value{color:var(--on-dark);word-break:break-word;line-height:1.6}
.site-footer__bottom{
  display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;
  gap:.75rem 1.5rem;padding-block:20px;
  border-top:1px solid var(--on-dark-line);
  font-family:var(--font-mono);font-size:.68rem;letter-spacing:.08em;color:var(--on-dark-dim);
}
.footer-copy{color:inherit}
.footer-legal{display:flex;flex-wrap:wrap;gap:.4rem 1.25rem}
.footer-legal a{color:inherit;transition:color 200ms var(--ease)}
.footer-legal a:hover,.footer-legal a:focus-visible{
  color:var(--paper);
  text-decoration:underline;text-underline-offset:3px;text-decoration-color:var(--highlight);
}

/* 7. 响应式 */
@media (min-width:640px){
  .site-footer__main{grid-template-columns:repeat(2,minmax(0,1fr))}
}
@media (min-width:1024px){
  .site-footer__main{grid-template-columns:1.5fr 1fr 1fr 1.5fr}
}

@media (max-width:960px){
  :root{--header-h:64px}
  .site-header__inner{gap:12px}
  .brand__mark{width:30px;height:30px}
  .site-nav{
    position:fixed;top:var(--header-h);left:0;right:0;
    display:none;flex-direction:column;justify-content:flex-start;align-items:stretch;
    max-height:calc(100dvh - var(--header-h));overflow-y:auto;
    padding:6px var(--pad) 26px;
    background-color:var(--paper);color:var(--ink);
    border-bottom:1px solid var(--line-strong);
    border-top:1px solid var(--line);
  }
  .site-nav[data-open="true"]{display:flex}
  .site-nav__list{flex-direction:column;align-items:stretch;gap:0;width:100%}
  .site-nav__link{display:block;padding-block:.9em;font-size:1rem;opacity:1;border-bottom:1px dashed var(--line);color:var(--ink)}
  .site-nav__link::after{display:none}
  .site-nav__link[aria-current="page"]{padding-left:.9em;border-left:3px solid var(--autumn);font-weight:700}
  .site-nav__extra{display:grid;gap:.5rem;margin-top:1.35rem;padding-top:1.1rem;border-top:1px solid var(--line-strong)}
  .nav-toggle{display:inline-flex}
  .site-header[data-open="true"]{background-color:var(--paper);border-bottom-color:var(--line-strong);color:var(--ink)}
  .site-header[data-open="true"] .brand__core{fill:var(--ink)}
  .site-header[data-open="true"] .brand__meta{color:var(--pencil)}
  .site-header[data-scrolled="true"] .site-nav{color:var(--ink)}
  body.has-nav-open{overflow:hidden}
}

@media (max-width:700px){
  .brand__meta{display:none}
  .version-pill{padding:.45em .8em;font-size:.66rem}
  .archive-band__note{display:none}
}

@media (max-width:400px){
  .brand__name{font-size:1.05rem}
  .nav-toggle__label{display:none}
  .nav-toggle{padding:.5em .7em}
}

/* 8. 动效降级 */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    transition-duration:.01ms !important;
    animation-duration:.01ms !important;
    animation-iteration-count:1 !important;
  }
  .btn:hover,.card:hover,.card:focus-within{transform:none}
  .card:hover::after,.card:focus-within::after{transform:translate(4px,4px)}
  .archive-band:hover .archive-band__arrow{transform:none}
}