/* Optical Metrology Notes — plain CSS, no external fonts or scripts */
:root {
  --bg: #ffffff; --fg: #1f2937; --muted: #6b7280; --line: #e5e7eb; --soft: #f8fafc;
  --accent: #1d4ed8; --accent-soft: #eff6ff;
  --code-bg: #f6f8fa; --code-fg: #24292f;
  --note-bg: #eff6ff; --note-line: #60a5fa; --warn-bg: #fff7ed; --warn-line: #fb923c;
  --measure: 44rem;
  --sans: system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", "Hiragino Sans GB", sans-serif;
  --mono: ui-monospace, "Cascadia Mono", "SF Mono", Consolas, Menlo, "Liberation Mono", monospace;
  --math: "Cambria Math", "STIX Two Math", "Latin Modern Math", "Noto Sans Math", math;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0e1116; --fg: #d6dde6; --muted: #8b95a5; --line: #263041; --soft: #151b24;
    --accent: #7eaaff; --accent-soft: #14213a;
    --code-bg: #151b24; --code-fg: #d6dde6;
    --note-bg: #12233d; --note-line: #3b82f6; --warn-bg: #2a1d10; --warn-line: #f59e0b;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 1rem; }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font: 17px/1.8 var(--sans); overflow-wrap: break-word;
}
a { color: var(--accent); text-decoration-thickness: .08em; text-underline-offset: .18em; }
a:hover { text-decoration-thickness: .14em; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 3px; }

/* ---------- layout ---------- */
.site-header, main, .site-footer { width: 100%; max-width: calc(var(--measure) + 2rem); margin-inline: auto; padding-inline: 1rem; }
.site-header { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding-block: 1rem; border-bottom: 1px solid var(--line); }
.brand { display: inline-flex; align-items: center; gap: .6rem; font-weight: 700; font-size: 1.05rem; color: var(--fg); text-decoration: none; }
.brand-mark { width: 1.5rem; height: 1.5rem; border-radius: .4rem; background: #2563eb url("/favicon.svg") center / cover; flex: none; }
.site-nav { display: flex; gap: 1.1rem; font-size: .95rem; }
.site-nav a { color: var(--muted); text-decoration: none; }
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--fg); }
.site-nav a[aria-current="page"] { text-decoration: underline; text-underline-offset: .35em; }
main { padding-block: 2rem 3rem; min-height: 60vh; }
.site-footer { padding-block: 1.5rem 3rem; border-top: 1px solid var(--line); color: var(--muted); font-size: .85rem; line-height: 1.7; }
.site-footer p { margin: .2rem 0; }

/* ---------- home ---------- */
.hero h1 { font-size: 2rem; line-height: 1.3; margin: .4rem 0 0; }
.subtitle { color: var(--muted); margin: .2rem 0 0; font-size: .95rem; }
.hero p:last-child { margin-top: 1rem; }
.section-title { font-size: 1.15rem; margin: 2.2rem 0 .8rem; padding-bottom: .4rem; border-bottom: 1px solid var(--line); }
.cards { list-style: none; padding: 0; margin: 0; display: grid; gap: .9rem; }
.card-link { display: block; padding: 1rem 1.15rem; border: 1px solid var(--line); border-radius: .7rem; background: var(--soft); color: inherit; text-decoration: none; transition: border-color .15s, transform .15s; }
.card-link:hover { border-color: var(--accent); transform: translateY(-1px); }
.card h2 { font-size: 1.12rem; line-height: 1.5; margin: 0; color: var(--fg); }
.card p { margin: .5rem 0 0; font-size: .95rem; line-height: 1.7; }
.card .subtitle { margin-top: .1rem; font-size: .85rem; }
.meta { display: flex; flex-wrap: wrap; align-items: center; gap: .4rem; color: var(--muted); font-size: .85rem; }
.tag { display: inline-block; padding: 0 .55rem; line-height: 1.55rem; border-radius: 999px; background: var(--accent-soft); color: var(--accent); font-size: .78rem; }
time { margin-right: .3rem; }

/* ---------- note ---------- */
.note-head { margin-bottom: 1.5rem; }
.kicker { margin: 0 0 .4rem; font-size: .85rem; }
.note-head h1 { font-size: 1.85rem; line-height: 1.4; margin: 0; }
.note-head .meta { margin-top: .8rem; }
.toc { border: 1px solid var(--line); border-radius: .6rem; background: var(--soft); padding: .8rem 1.1rem; margin: 1.2rem 0 1.6rem; font-size: .93rem; }
.toc ol { margin: .4rem 0 0; padding-left: 1.3rem; line-height: 1.75; }
.prose h2 { font-size: 1.35rem; line-height: 1.5; margin: 2.4rem 0 .8rem; padding-top: .3rem; }
.prose h3 { font-size: 1.1rem; margin: 1.8rem 0 .6rem; }
.prose p, .prose ul, .prose ol { margin: .9rem 0; }
.prose li { margin: .25rem 0; }
.prose li > p { margin: .3rem 0; }
.anchor { margin-left: .4rem; color: var(--muted); text-decoration: none; opacity: 0; font-weight: 400; }
h2:hover .anchor, h3:hover .anchor, .anchor:focus { opacity: .8; }
hr { border: 0; border-top: 1px solid var(--line); margin: 2rem 0; }

/* figures */
figure { margin: 1.8rem 0; }
figure img { display: block; width: 100%; height: auto; background: #fff; border: 1px solid var(--line); border-radius: .5rem; }
figcaption { margin-top: .5rem; color: var(--muted); font-size: .88rem; line-height: 1.65; }

/* callouts: ::: note / ::: warn */
.note-callout, div.note, div.warn { margin: 1.3rem 0; padding: .8rem 1.1rem; border-left: 4px solid var(--note-line); background: var(--note-bg); border-radius: 0 .5rem .5rem 0; font-size: .96rem; line-height: 1.75; }
div.warn { border-left-color: var(--warn-line); background: var(--warn-bg); }
div.note::before, div.warn::before { display: block; font-weight: 700; font-size: .8rem; letter-spacing: .06em; margin-bottom: .2rem; }
div.note::before { content: "备注"; color: var(--accent); }
div.warn::before { content: "注意"; color: var(--warn-line); }
div.note > p, div.warn > p { margin: .35rem 0; }

/* tables */
.table-wrap { margin: 1.3rem 0; overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: .93rem; line-height: 1.6; }
th, td { padding: .5rem .75rem; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
thead th { border-bottom: 2px solid var(--line); background: var(--soft); white-space: nowrap; }
tbody tr:last-child td { border-bottom-color: var(--line); }

/* math (MathML, rendered natively by the browser) */
math { font-family: var(--math); font-size: 1.1em; }
math[display="block"] { display: block math; margin: 1.1em 0; overflow-x: auto; overflow-y: hidden; padding: .2em 0; }

/* code */
code, pre { font-family: var(--mono); }
code { font-size: .88em; background: var(--code-bg); padding: .12em .35em; border-radius: .3em; }
div.sourceCode { margin: 1.2rem 0; background: var(--code-bg); border: 1px solid var(--line); border-radius: .5rem; overflow-x: auto; }
pre { margin: 0; padding: .9rem 1.1rem; overflow-x: auto; font-size: .84rem; line-height: 1.6; color: var(--code-fg); tab-size: 4; }
pre code { background: none; padding: 0; font-size: inherit; }
pre > code.sourceCode > span { display: inline-block; min-height: 1.6em; }
code span.kw, code span.cf { color: #cf222e; font-weight: 600 }
code span.dt, code span.bu { color: #0550ae }
code span.dv, code span.bn, code span.fl { color: #0a3069 }
code span.st, code span.ch, code span.vs, code span.ss, code span.sc { color: #0a3069 }
code span.co { color: #6e7781; font-style: italic }
code span.fu, code span.ex { color: #8250df }
code span.op { color: #cf222e }
code span.im, code span.pp { color: #953800 }
code span.at, code span.va, code span.cn, code span.ot, code span.do, code span.an, code span.cv, code span.in { color: #116329 }
code span.al, code span.er, code span.wa { color: #cf222e; font-weight: 600 }
@media (prefers-color-scheme: dark) {
  code span.kw, code span.cf, code span.op, code span.al, code span.er, code span.wa { color: #ff7b72 }
  code span.dt, code span.bu { color: #79c0ff }
  code span.dv, code span.bn, code span.fl, code span.st, code span.ch, code span.vs, code span.ss, code span.sc { color: #a5d6ff }
  code span.co { color: #8b949e }
  code span.fu, code span.ex { color: #d2a8ff }
  code span.im, code span.pp { color: #ffa657 }
  code span.at, code span.va, code span.cn, code span.ot, code span.do, code span.an, code span.cv, code span.in { color: #7ee787 }
}
/* pandoc line anchors inside code blocks */
pre > code.sourceCode > span > a:first-child::before { text-decoration: none; }

/* ---------- small screens ---------- */
@media (max-width: 600px) {
  body { font-size: 16px; }
  .hero h1, .note-head h1 { font-size: 1.55rem; }
  .site-header { flex-wrap: wrap; }
  .card-link { padding: .9rem 1rem; }
  th, td { padding: .45rem .55rem; min-width: 6em; }   /* wide tables scroll sideways instead of crushing the text */
}
@media print {
  .site-header, .site-footer, .anchor, .toc { display: none; }
  body { font-size: 11pt; }
  a { color: inherit; }
}