/* ------------------------------------------------------------------
   ah! · 人工智能历史社区
   色值取自 ah! brand kit（colors/tokens.css，与 Figma「ah! colour」同源）
   字体一律走系统栈：站点不向任何第三方 CDN 发请求
   ------------------------------------------------------------------ */

:root {
  /* 品牌原色 */
  --ink: #1C1917;
  --paper: #F5F5F5;
  --grey-50: #FAFAF9;
  --grey-100: #F5F5F5;
  --grey-200: #E7E5E4;
  --grey-300: #D6D3D1;
  --grey-400: #A8A29E;
  --grey-500: #78716C;
  --grey-600: #57534E;
  --grey-700: #44403C;
  --grey-800: #292524;
  --grey-900: #1C1917;
  --grey-950: #0C0A09;
  --dot-red: #C8102E;
  --dot-blue: #1F70C1;
  --dot-green: #2FBF71;

  /* 语义色 · 浅色 */
  --text-primary: var(--ink);
  --text-secondary: var(--grey-600);
  --text-muted: var(--grey-500);
  --rule: var(--grey-300);
  --rule-soft: var(--grey-200);
  --surface-bg: var(--paper);
  --surface-raised: #FFFFFF;
  --surface-sunken: var(--grey-200);
  --link: var(--dot-blue);
  --link-visited: #6B4FA8;
  --mark: rgba(200, 16, 46, .10);

  --font-serif: "Songti SC", "STSong", "Source Han Serif SC", "Noto Serif CJK SC",
                "Noto Serif SC", SimSun, "Times New Roman", Georgia, serif;
  --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
               "Noto Sans CJK SC", -apple-system, "Segoe UI", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, Menlo, Consolas, "Courier New", monospace;

  --col: 40rem;      /* 正文栏宽 */
  --gutter: 14rem;   /* 右侧边注栏 */
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --text-primary: var(--paper);
    --text-secondary: var(--grey-400);
    --text-muted: var(--grey-500);
    --rule: var(--grey-700);
    --rule-soft: var(--grey-800);
    --surface-bg: var(--ink);
    --surface-raised: var(--grey-800);
    --surface-sunken: var(--grey-950);
    --link: #7FB3E8;
    --link-visited: #B49BDD;
    --mark: rgba(200, 16, 46, .22);
  }
}
:root[data-theme="dark"] {
  --text-primary: var(--paper);
  --text-secondary: var(--grey-400);
  --text-muted: var(--grey-500);
  --rule: var(--grey-700);
  --rule-soft: var(--grey-800);
  --surface-bg: var(--ink);
  --surface-raised: var(--grey-800);
  --surface-sunken: var(--grey-950);
  --link: #7FB3E8;
  --link-visited: #B49BDD;
  --mark: rgba(200, 16, 46, .22);
}

/* ---------------------------------------------------------------- base */

*, *::before, *::after { box-sizing: border-box; }

html {
  font-size: 100%;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--surface-bg);
  color: var(--text-primary);
  font-family: var(--font-serif);
  font-size: 1.0625rem;
  line-height: 1.95;
  letter-spacing: .01em;
  font-kerning: normal;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--link);
  text-decoration: none;
  border-bottom: 1px dotted currentColor;
  transition: border-bottom-style .12s ease;
}
a:hover { border-bottom-style: solid; }
.topnav a, .brand, .colophon a, .record-links a, details.past summary {
  border-bottom: 1px solid transparent;
}
.topnav a:hover, .colophon a:hover, .record-links a:hover {
  border-bottom: 1px solid currentColor;
}
a:visited { color: var(--link-visited); }
a:focus-visible {
  outline: 2px solid var(--dot-red);
  outline-offset: 2px;
  border-radius: 2px;
}

::selection { background: var(--mark); }

/* --------------------------------------------------------------- shell */

.wrap {
  max-width: 47.5rem;
  margin: 0 auto;
  padding: 0 1.5rem;
  position: relative;
}

.column { max-width: var(--col); }

/* -------------------------------------------------------------- header */

.masthead {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
  padding: 2.75rem 0 .7rem;
  border-bottom: 1px solid var(--rule-soft);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .625rem;
  border: none;
  color: var(--text-primary);
}
.brand:visited { color: var(--text-primary); }
.brand:hover { border: none; }
.brand svg {
  height: 1.55rem;
  width: auto;
  display: block;
  color: var(--text-primary);
}
.brand svg #dot { fill: var(--dot-red); }
.brand:hover svg #dot { fill: var(--dot-blue); }
.brand .brand-rule {
  width: 1px;
  height: 1.15rem;
  background: var(--rule);
  display: inline-block;
}
.brand .brand-sub {
  font-family: var(--font-sans);
  font-size: .8125rem;
  letter-spacing: .12em;
  color: var(--text-muted);
  white-space: nowrap;
}

.topnav {
  font-family: var(--font-sans);
  font-size: .875rem;
  letter-spacing: .06em;
  display: flex;
  gap: 1.15rem;
  flex-wrap: wrap;
}
.topnav a { color: var(--text-secondary); }
.topnav a:hover { color: var(--text-primary); }
.topnav a[aria-current="page"] {
  color: var(--text-primary);
  border-bottom: 1px solid var(--dot-red);
}

/* ---------------------------------------------------------------- main */

main { padding: 2rem 0 1rem; }

.lede {
  margin: 0 0 2.25rem;
}

h1, h2, h3, h4 {
  font-family: var(--font-sans);
  font-weight: 600;
  line-height: 1.45;
  letter-spacing: .01em;
  color: var(--text-primary);
}
h1 { font-size: 1.6875rem; margin: 0 0 1.25rem; }
h2 { font-size: 1.25rem;   margin: 2.5rem 0 .9rem; }
h3 { font-size: 1rem; margin: 2rem 0 .6rem; }
h4 { font-size: .9375rem; margin: 1.5rem 0 .4rem; color: var(--text-secondary); }

h2 + h3 { margin-top: 1.25rem; }

p { margin: 0 0 1.15rem; }

ul, ol { margin: 0 0 1.15rem; padding-left: 1.4rem; }
li { margin: 0 0 .35rem; }
li > ul, li > ol { margin-top: .35rem; }

hr {
  border: 0;
  border-top: 1px solid var(--rule-soft);
  margin: 2.5rem 0;
}

blockquote {
  margin: 1.5rem 0;
  padding-left: 1.1rem;
  border-left: 2px solid var(--rule);
  color: var(--text-secondary);
}
blockquote p:last-child { margin-bottom: 0; }

code, kbd, samp {
  font-family: var(--font-mono);
  font-size: .875em;
  background: var(--surface-sunken);
  padding: .1em .35em;
  border-radius: 3px;
}
pre {
  font-family: var(--font-mono);
  font-size: .8125rem;
  line-height: 1.7;
  background: var(--surface-sunken);
  padding: .9rem 1.1rem;
  border-radius: 4px;
  overflow-x: auto;
}
pre code { background: none; padding: 0; }

strong { font-weight: 600; }
em { font-style: italic; }

table {
  border-collapse: collapse;
  width: 100%;
  font-size: .9375rem;
  margin: 1.5rem 0;
}
th, td {
  text-align: left;
  padding: .5rem .75rem .5rem 0;
  border-bottom: 1px solid var(--rule-soft);
  vertical-align: top;
}
th {
  font-family: var(--font-sans);
  font-size: .75rem;
  letter-spacing: .1em;
  color: var(--text-muted);
  font-weight: 500;
}

img { max-width: 100%; height: auto; }

/* -------------------------------------------------------- 边注 sidenote */

.sidenote {
  float: right;
  clear: right;
  width: var(--gutter);
  margin-right: calc(-1 * (var(--gutter) + 2rem));
  margin-top: .35rem;
  margin-bottom: 1rem;
  font-family: var(--font-sans);
  font-size: .8125rem;
  line-height: 1.75;
  color: var(--text-secondary);
}
.sidenote-number {
  font-family: var(--font-sans);
  font-size: .6875rem;
  vertical-align: super;
  line-height: 0;
  color: var(--dot-red);
  padding-left: .1em;
}

/* ------------------------------------------------------------ 条目列表 */

.entry-list { margin: 0 0 1rem; }

.entry {
  display: grid;
  grid-template-columns: 1fr auto auto;
  align-items: baseline;
  gap: 0 1rem;
  padding: .55rem 0 .45rem;
  border-bottom: 1px dotted var(--rule);
}
.entry-title { min-width: 0; }
.entry-title > a {
  display: block;
  padding-bottom: .12rem;
}
.entry-meta-row { display: flex; gap: .9rem; }
.entry-kind, .entry-date {
  font-family: var(--font-sans);
  font-size: .6875rem;
  letter-spacing: .14em;
  white-space: nowrap;
}
.entry-kind a, .entry-kind { color: var(--text-muted); }
.entry-kind a:hover { color: var(--text-primary); }
.entry-date {
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

/* ------------------------------------------------------- 项目 / 活动块 */

.record { margin: 0 0 2.5rem; }
.record:last-child { margin-bottom: 0; }

.record-head {
  display: flex;
  align-items: baseline;
  gap: .75rem;
  flex-wrap: wrap;
  margin: 0 0 .5rem;
}
.record-head h3 { margin: 0; font-size: 1.125rem; }
.record-tag {
  font-family: var(--font-sans);
  font-size: .6875rem;
  letter-spacing: .14em;
  color: var(--text-muted);
}
.record-body { margin: 0 0 .5rem; color: var(--text-primary); }
.record-body p:last-child { margin-bottom: 0; }
.record-status {
  font-style: italic;
  color: var(--text-secondary);
  margin: .5rem 0 0;
}
.record-links {
  font-family: var(--font-sans);
  font-size: .8125rem;
  margin: .6rem 0 0;
  display: flex;
  gap: 1.1rem;
  flex-wrap: wrap;
}

.session {
  display: grid;
  grid-template-columns: 5.5rem 1fr;
  gap: 0 1.25rem;
  padding: .85rem 0;
  border-bottom: 1px dotted var(--rule);
  align-items: baseline;
}
.session-when {
  font-family: var(--font-sans);
  font-size: .8125rem;
  color: var(--text-secondary);
  font-variant-numeric: tabular-nums;
  line-height: 1.6;
}
.session-when .session-time { display: block; color: var(--text-muted); font-size: .75rem; }
.session-what { min-width: 0; }
.session-title { margin: 0 0 .15rem; }
.session-meta {
  font-family: var(--font-sans);
  font-size: .8125rem;
  color: var(--text-muted);
  margin: 0;
}
.session.is-past .session-title { color: var(--text-secondary); }

details.past {
  margin: 1.75rem 0 0;
}
details.past > summary {
  font-family: var(--font-sans);
  font-size: .75rem;
  letter-spacing: .12em;
  color: var(--text-muted);
  cursor: pointer;
  list-style: none;
  padding: .3rem 0;
}
details.past > summary::-webkit-details-marker { display: none; }
details.past > summary::before {
  content: "▶";
  font-size: .6875rem;
  margin-right: .45rem;
  display: inline-block;
  transition: transform .15s ease;
}
details.past[open] > summary::before { transform: rotate(90deg); }
details.past > summary:hover { color: var(--text-primary); }
details.past .session:first-of-type { border-top: 1px dotted var(--rule); }

/* ------------------------------------------------------------- 文章页 */

.post-meta {
  font-family: var(--font-sans);
  font-size: .75rem;
  letter-spacing: .12em;
  color: var(--text-muted);
  margin: -.5rem 0 2rem;
  display: flex;
  gap: .9rem;
  flex-wrap: wrap;
}

.post-body > :first-child { margin-top: 0; }

.footnotes {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule-soft);
  font-size: .9375rem;
  color: var(--text-secondary);
}
.footnotes ol { padding-left: 1.2rem; }

.post-nav {
  margin-top: 3rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--rule-soft);
  font-family: var(--font-sans);
  font-size: .875rem;
}

/* -------------------------------------------------------------- 搜索 */

#search-input {
  width: 100%;
  font-family: var(--font-serif);
  font-size: 1.0625rem;
  color: var(--text-primary);
  background: var(--surface-raised);
  border: 1px solid var(--rule);
  border-radius: 3px;
  padding: .6rem .75rem;
  line-height: 1.6;
}
#search-input:focus {
  outline: none;
  border-color: var(--dot-blue);
}
#search-count {
  font-family: var(--font-sans);
  font-size: .75rem;
  letter-spacing: .1em;
  color: var(--text-muted);
  margin: .85rem 0 .5rem;
}
.search-hit-excerpt {
  font-size: .9375rem;
  color: var(--text-secondary);
  margin: .2rem 0 0;
}
.search-hit-excerpt mark { background: var(--mark); color: inherit; }

/* -------------------------------------------------------------- 页脚 */

.colophon {
  margin-top: 4.5rem;
  padding: 1.5rem 0 3.5rem;
  border-top: 1px solid var(--rule-soft);
  font-family: var(--font-sans);
  font-size: .8125rem;
  color: var(--text-muted);
}
.colophon nav { line-height: 2; }
.colophon nav > span { color: var(--text-muted); }
.colophon a { color: var(--text-secondary); }
.colophon a:hover { color: var(--text-primary); }
.colophon p { margin: 0 0 .35rem; }

/* ------------------------------------------------------- 边角涂鸦 */

.doodle {
  position: absolute;
  color: var(--grey-400);
  opacity: .55;
  pointer-events: none;
  user-select: none;
}
.doodle svg { display: block; width: 100%; height: auto; }
.doodle-1 { top: 16rem;  right: -3rem;   width: 5rem; }
.doodle-2 { bottom: 2rem; left: -5rem;    width: 5.5rem; }  /* 贴着页脚，页面长短都不飘 */
.doodle-3 { top: 56rem;  right: -2.5rem; width: 5.5rem; }
.doodle-4 { top: 80rem;  left: -4.5rem;  width: 4.5rem; }

@media (max-width: 1320px) {
  .doodle { display: none; }
}

/* ------------------------------------------------------------ 窄屏 */

@media (max-width: 1180px) {
  .sidenote {
    float: none;
    width: auto;
    margin: .75rem 0 1.25rem;
    padding-left: .9rem;
    border-left: 2px solid var(--rule-soft);
  }
}

@media (max-width: 640px) {
  body { font-size: 1rem; line-height: 1.85; }
  .wrap { padding: 0 1.125rem; }
  .masthead { padding-top: 1.75rem; gap: .9rem; }
  .topnav { gap: .85rem; font-size: .8125rem; }
  .lede { font-size: 1.0625rem; }
  h1 { font-size: 1.4375rem; }

  .entry {
    grid-template-columns: 1fr;
    gap: .15rem;
    padding: .7rem 0;
  }
  .entry-kind, .entry-date { grid-column: 1; }
  .session {
    grid-template-columns: 1fr;
    gap: .2rem;
  }
  .session-when .session-time { display: inline; margin-left: .5rem; }
}

@media print {
  .topnav, .colophon nav, .doodle { display: none; }
  body { background: #fff; color: #000; font-size: 11pt; }
  a { color: #000; }
}

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}