/* ============================================================
   Richard Tang personal site
   Minimal research portfolio. System fonts, single column,
   near-monochrome, no motion. No framework, no JS.
   ============================================================ */

:root {
  --bg:    #fcfbf9;
  --text:  #1b1a18;
  --muted: #6f6b63;
  --faint: #98938a;
  --line:  #e5e1d8;
  --maxw:  760px;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    Helvetica, Arial, sans-serif;
  font-size: 17px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { max-width: 100%; display: block; }

a { color: var(--text); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ---------- nav ---------- */
.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  padding: 22px 0;
  font-size: 15px;
}
.nav__name { font-weight: 700; }
.nav__links a { color: var(--muted); }
.nav__links a + a { margin-left: 18px; }
.nav__links a:hover { color: var(--text); }
.nav__links a[aria-current="page"] { color: var(--text); font-weight: 600; }

/* ---------- intro ---------- */
.intro {
  display: flex;
  gap: 28px;
  align-items: center;
  justify-content: space-between;
  margin: 24px 0 0;
}
.intro h1 { font-size: 1.7rem; font-weight: 700; margin: 0 0 5px; letter-spacing: -0.01em; }
.intro__role { color: var(--muted); margin: 0; }
.intro__photo {
  width: 120px; height: 120px; flex: none;
  object-fit: cover; border-radius: 6px;
  margin-right: 28px;
}
.bio { margin: 20px 0 0; }
.bio p { margin: 0 0 12px; }
.meta-links { margin: 14px 0 0; color: var(--muted); font-size: 15px; }
.meta-links a { color: var(--muted); }
.meta-links a:hover { color: var(--text); }

/* thin rule / divider */
.rule { border: none; border-top: 1px solid var(--line); margin: 24px 0; }
.rule + .bio { margin-top: 0; }

/* ---------- sections ---------- */
section { margin-top: 48px; }
h2.label {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  font-weight: 700;
  color: var(--muted);
  margin: 0 0 18px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line);
}
.section-link { float: right; font-weight: 400; text-transform: none; letter-spacing: 0; font-size: 0.85rem; }

/* group heading inside the projects list */
h3.group {
  font-size: 1.05rem;
  font-weight: 700;
  margin: 32px 0 14px;
}
h3.group:first-of-type { margin-top: 0; }

/* ---------- entries (experience + projects) ---------- */
.entry { margin-bottom: 22px; }
.entry__head {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: baseline;
  gap: 4px 16px;
}
.entry__title { font-weight: 600; }
.entry__org { color: var(--muted); font-weight: 400; }
.medal {
  display: inline-block;
  vertical-align: -0.22em;
  line-height: 0;
}
.medal__icon {
  display: block;
  width: 1.15em;
  height: 1.38em;
}
.medal--bronze .medal__ribbon { fill: #7a5f3f; }
.medal--bronze .medal__disc { fill: #a67c52; }
.medal--bronze .medal__shine {
  fill: none;
  stroke: rgba(255, 255, 255, 0.28);
  stroke-width: 0.75;
}
.entry__date {
  color: var(--muted); font-size: 14px; white-space: nowrap;
  font-variant-numeric: tabular-nums;
}
.entry--collapsible {
  interpolate-size: allow-keywords;
}
.entry--collapsible > summary.entry__head {
  list-style: none;
  cursor: pointer;
  margin: 0 -8px;
  padding: 4px 8px;
  border-radius: 4px;
  transition: background-color 0.18s ease;
}
.entry--collapsible > summary.entry__head::-webkit-details-marker { display: none; }
.entry--collapsible > summary.entry__head::marker { content: ""; }
.entry--collapsible > summary.entry__head:hover {
  background-color: #f3efe6;
}
.entry--collapsible > summary.entry__head .entry__date {
  margin-left: auto;
}
.entry--collapsible > summary.entry__head::after {
  content: "";
  flex-shrink: 0;
  align-self: center;
  width: 7px;
  height: 7px;
  margin-left: 10px;
  border-right: 1.5px solid var(--faint);
  border-bottom: 1.5px solid var(--faint);
  transform: rotate(-45deg);
  transition: transform 0.24s ease, border-color 0.18s ease;
}
.entry--collapsible > summary.entry__head:hover::after {
  border-color: var(--muted);
}
.entry--collapsible[open] > summary.entry__head::after {
  transform: rotate(45deg);
}
.entry--collapsible .entry__panel {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.28s ease;
}
.entry--collapsible[open] .entry__panel {
  grid-template-rows: 1fr;
}
.entry--collapsible .entry__panel-inner {
  overflow: hidden;
  min-height: 0;
  opacity: 0;
  transition: opacity 0.22s ease;
}
.entry--collapsible[open] .entry__panel-inner {
  opacity: 1;
}
.entry--collapsible .entry__desc { margin: 6px 0 0; }

@supports selector(details::details-content) {
  .entry--collapsible::details-content {
    height: 0;
    overflow: hidden;
    opacity: 0;
    transition:
      height 0.28s ease,
      opacity 0.22s ease 0.04s,
      content-visibility 0.28s allow-discrete;
  }
  .entry--collapsible[open]::details-content {
    height: auto;
    opacity: 1;
    transition:
      height 0.28s ease,
      opacity 0.24s ease 0.06s,
      content-visibility 0.28s allow-discrete;
  }
  .entry--collapsible .entry__panel {
    display: block;
    grid-template-rows: unset;
    transition: none;
  }
  .entry--collapsible .entry__panel-inner {
    opacity: 1;
    transition: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .entry--collapsible,
  .entry--collapsible > summary.entry__head,
  .entry--collapsible > summary.entry__head::after,
  .entry--collapsible .entry__panel,
  .entry--collapsible .entry__panel-inner {
    transition: none;
  }
  @supports selector(details::details-content) {
    .entry--collapsible::details-content {
      transition: none;
    }
  }
}
.entry__meta { margin: 4px 0 0; color: var(--muted); font-size: 14px; }
.entry__meta a { color: var(--muted); text-decoration: underline; text-decoration-color: var(--line); text-underline-offset: 2px; }
.entry__meta a:hover { color: var(--text); text-decoration-color: currentColor; }
.entry__list { margin: 6px 0 0; padding-left: 20px; }
.entry__list li { margin-top: 4px; }
.entry__list li::marker { color: var(--faint); }

/* ---------- compact sections (experience + highlights) ---------- */
.section--compact { margin-top: 36px; }
.section--compact > h2.label {
  margin-bottom: 10px;
  padding-bottom: 6px;
}
.section--compact > h3.group {
  margin: 16px 0 6px;
  font-size: 1rem;
}
.section--compact .entry { margin-bottom: 10px; }
.section--compact .entry:last-child { margin-bottom: 0; }
.section--compact .entry--collapsible > summary.entry__head {
  padding: 1px 8px;
}
.section--compact .entry__head { gap: 2px 12px; }
.section--compact .entry__date { font-size: 13px; }
.section--compact .entry__list {
  margin: 3px 0 0;
  padding-left: 18px;
}
.section--compact .entry__list li { margin-top: 2px; }
.section--compact .entry__meta {
  margin: 2px 0 0;
  font-size: 13px;
}
.section--compact .entry--collapsible .entry__desc { margin: 3px 0 0; }

/* ---------- blog list ---------- */
.posts { list-style: none; margin: 0; padding: 0; }
.posts li {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 16px;
  padding: 11px 0;
  border-bottom: 1px solid var(--line);
}
.posts li:first-child { border-top: 1px solid var(--line); }
.post__cat {
  color: var(--faint); font-size: 12px; text-transform: uppercase;
  letter-spacing: 0.06em; margin-right: 10px;
}
.post__date { color: var(--muted); font-size: 14px; white-space: nowrap; font-variant-numeric: tabular-nums; }

/* ---------- article (post) ---------- */
.article { margin: 28px 0 0; }
.article__date { color: var(--muted); font-size: 14px; }
.article h1 { font-size: 1.9rem; font-weight: 700; margin: 6px 0 0; letter-spacing: -0.01em; }
.prose { margin-top: 28px; }
.prose > * + * { margin-top: 16px; }
.prose h2 { font-size: 1.2rem; font-weight: 700; margin-top: 32px; }
.prose a { text-decoration: underline; text-decoration-color: #c4bdb1; text-underline-offset: 2px; }
.prose a:hover { text-decoration-color: currentColor; }
.prose ul { padding-left: 22px; }
.prose li + li { margin-top: 6px; }
.prose code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.88em; background: #f1ede4; padding: 0.08em 0.36em; border-radius: 4px;
}
.prose pre { background: #f1ede4; padding: 14px 16px; border-radius: 6px; overflow-x: auto; }
.prose pre code { background: none; padding: 0; }
.backlink { display: inline-block; margin-top: 36px; color: var(--muted); }

/* ---------- footer ---------- */
.footer {
  margin: 72px 0 48px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 14px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.footer a { color: var(--muted); }
.footer a:hover { color: var(--text); }

/* ---------- responsive ---------- */
@media (max-width: 560px) {
  .intro { flex-direction: column-reverse; align-items: flex-start; gap: 18px; }
  .entry__head { flex-direction: column; gap: 2px; }
  .entry--collapsible > summary.entry__head::after {
    align-self: flex-start;
    margin-left: 0;
    margin-top: 4px;
  }
}