/* Chenglei Yu — personal homepage
   Editorial academic style: warm paper, serif display type, one cinnabar accent.
   Layout rule: a fixed left column (--col) holds the portrait, paper thumbnails and dates,
   so every section shares one vertical axis. */

:root {
  --bg: #faf8f4;
  --surface: #ffffff;
  --tint: #f3eee3;
  --ink: #1c1b18;
  --ink-2: #44423c;
  --muted: #77736a;
  --rule: #e6e1d6;
  --accent: #b5412b;
  --link: #245d92;
  --link-hover: #153f68;
  --thumb-bg: #ffffff;
  --shadow: 0 1px 2px rgb(28 27 24 / 0.05), 0 10px 28px -14px rgb(28 27 24 / 0.22);

  --serif: "Newsreader", "Iowan Old Style", Charter, "Palatino Linotype", Palatino, Georgia, "Songti SC", "Noto Serif SC", serif;
  --sans: "Source Sans 3", -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  --maxw: 900px;
  --col: 200px;
  --gap: 40px;
  --pad: 24px;

  color-scheme: light;
}

/* Dark theme. data-theme is set before first paint by the inline script in index.html
   (saved choice, else the system setting) and flipped by the toggle in the top bar. */
:root[data-theme="dark"] {
  --bg: #131312;
  --surface: #1b1a18;
  --tint: #201e1a;
  --ink: #ede9e1;
  --ink-2: #c8c3b8;
  --muted: #8f8a7f;
  --rule: #2e2c28;
  --accent: #e27b62;
  --link: #8fb9e8;
  --link-hover: #bcd6f5;
  --thumb-bg: #f1eee8;
  --shadow: 0 1px 2px rgb(0 0 0 / 0.3), 0 10px 28px -14px rgb(0 0 0 / 0.6);

  color-scheme: dark;
}

:root[data-theme="dark"] .pub-thumb img { filter: brightness(0.94); }

/* ---------- Base ---------- */

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

[hidden] { display: none !important; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink-2);
  font: 400 16.5px/1.65 var(--sans);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

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

a {
  color: var(--link);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  text-decoration-color: color-mix(in srgb, currentColor 32%, transparent);
  transition: color 0.15s ease, text-decoration-color 0.15s ease;
}

a:hover {
  color: var(--link-hover);
  text-decoration-color: currentColor;
}

b, strong { color: var(--ink); font-weight: 650; }

::selection { background: color-mix(in srgb, var(--accent) 24%, transparent); }

:focus-visible {
  outline: 2px solid var(--link);
  outline-offset: 3px;
  border-radius: 4px;
}

.muted { color: var(--muted); }

.skip-link {
  position: absolute;
  top: -48px;
  left: 12px;
  z-index: 100;
  padding: 8px 12px;
  border-radius: 6px;
  background: var(--ink);
  color: var(--bg);
  text-decoration: none;
}

.skip-link:focus { top: 12px; }

/* ---------- Top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--bg);
  background: color-mix(in srgb, var(--bg) 84%, transparent);
  -webkit-backdrop-filter: saturate(1.3) blur(12px);
  backdrop-filter: saturate(1.3) blur(12px);
  border-bottom: 1px solid var(--rule);
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  max-width: var(--maxw);
  height: 58px;
  margin: 0 auto;
  padding: 0 var(--pad);
}

.brand {
  font-family: var(--serif);
  font-size: 1.22rem;
  font-weight: 500;
  letter-spacing: -0.005em;
  white-space: nowrap;
  color: var(--ink);
  text-decoration: none;
}

.brand:hover { color: var(--ink); }

.topbar-right { display: flex; align-items: center; gap: 22px; }

.topbar nav { display: flex; gap: 26px; }

.topbar nav a {
  font-size: 0.94rem;
  color: var(--muted);
  text-decoration: none;
}

.topbar nav a:hover { color: var(--ink); }

.theme-toggle {
  display: inline-grid;
  place-items: center;
  width: 34px;
  height: 34px;
  padding: 0;
  border: 1px solid var(--rule);
  border-radius: 999px;
  background: transparent;
  color: var(--ink-2);
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease;
}

.theme-toggle:hover {
  border-color: color-mix(in srgb, var(--ink) 35%, transparent);
  background: var(--surface);
  color: var(--ink);
}

.theme-toggle svg { width: 17px; height: 17px; }

/* Show the moon in light mode (go dark) and the sun in dark mode (go light) */
.theme-toggle .icon-sun,
:root[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

:root[data-theme="dark"] .theme-toggle .icon-sun { display: block; }

/* ---------- Page ---------- */

.page {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 var(--pad);
}

.hero {
  display: grid;
  grid-template-columns: var(--col) minmax(0, 1fr);
  gap: var(--gap);
  align-items: start;
  padding: 64px 0 8px;
  scroll-margin-top: 76px;
}

.portrait {
  width: 100%;
  aspect-ratio: 4 / 5;
  object-fit: cover;
  border-radius: 16px;
  background: var(--tint);
  box-shadow: var(--shadow);
}

.intro h1 {
  margin: -6px 0 6px;
  font-family: var(--serif);
  font-size: clamp(2.5rem, 1.9rem + 2.2vw, 3.25rem);
  font-weight: 500;
  line-height: 1.04;
  letter-spacing: -0.02em;
  color: var(--ink);
}

/* Chinese name: a Song/Ming serif to sit with Newsreader; stays on one line if it wraps */
.name-zh {
  margin-left: 0.28em;
  font-family: "Songti SC", STSong, "Source Han Serif SC", "Noto Serif SC", SimSun, serif;
  font-size: 0.52em;
  font-weight: 400;
  letter-spacing: 0.06em;
  white-space: nowrap;
  color: var(--muted);
}

.intro .tagline {
  margin: 0 0 22px;
  font-family: var(--serif);
  font-size: 1.22rem;
  font-style: italic;
  line-height: 1.4;
  color: var(--muted);
}

.intro p { margin: 0 0 14px; }

.contact {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 24px 0 0;
  padding: 0;
  list-style: none;
}

.contact a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 7px 14px 7px 12px;
  border: 1px solid var(--rule);
  border-radius: 999px;
  background: var(--surface);
  font-size: 0.9rem;
  line-height: 1.2;
  color: var(--ink-2);
  text-decoration: none;
  transition: border-color 0.2s ease, color 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}

.contact a:hover {
  border-color: color-mix(in srgb, var(--ink) 35%, transparent);
  color: var(--ink);
  transform: translateY(-1px);
  box-shadow: var(--shadow);
}

.contact svg { flex: none; width: 16px; height: 16px; }

/* ---------- Sections ---------- */

.block {
  margin-top: 64px;
  scroll-margin-top: 76px;
}

h2 {
  display: flex;
  align-items: center;
  gap: 18px;
  margin: 0 0 22px;
  font-family: var(--serif);
  font-size: 1.8rem;
  font-weight: 500;
  line-height: 1.2;
  letter-spacing: -0.01em;
  color: var(--ink);
}

h2::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--rule);
  transform: translateY(3px);
}

/* News + Experience: date in the left column, text in the right */
.timeline { margin: 0; padding: 0; list-style: none; }

.timeline li {
  display: grid;
  grid-template-columns: var(--col) minmax(0, 1fr);
  gap: var(--gap);
  align-items: baseline;
  padding: 6px 0;
}

.timeline time {
  font-size: 0.95rem;
  font-variant-numeric: tabular-nums;
  text-align: right;
  white-space: nowrap;
  color: var(--muted);
}

.timeline p { margin: 0; }

/* ---------- Publications ---------- */

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 22px;
  margin: -8px 0 26px;
  font-size: 0.88rem;
  color: var(--muted);
}

.swatch {
  display: inline-block;
  width: 12px;
  height: 12px;
  margin-right: 7px;
  border: 1px solid color-mix(in srgb, var(--ink) 18%, transparent);
  border-radius: 3px;
  background: var(--tint);
  vertical-align: -1px;
}

.group {
  margin: 34px 0 8px;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}

.legend + .group { margin-top: 0; }

.pubs {
  display: grid;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.pub {
  display: grid;
  grid-template-columns: var(--col) minmax(0, 1fr);
  gap: var(--gap);
  align-items: start;
  margin: 0 -18px;
  padding: 18px;
  border-radius: 16px;
  scroll-margin-top: 76px;
}

.pub.is-first { background: var(--tint); }

.pub-thumb {
  display: block;
  aspect-ratio: 16 / 10;
  padding: 8px;
  overflow: hidden;
  border: 1px solid var(--rule);
  border-radius: 10px;
  background: var(--thumb-bg);
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

.pub-thumb img { width: 100%; height: 100%; object-fit: contain; }

.pub-thumb:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

/* Venue names keep their own casing (NeurIPS, arXiv); only the award pill is uppercased. */
.venue {
  margin: 0 0 5px;
  font-size: 0.84rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--accent);
}

.venue.is-preprint { color: var(--muted); }

.award {
  display: inline-block;
  margin-left: 6px;
  padding: 1px 7px;
  border-radius: 999px;
  background: var(--accent);
  font-size: 0.66rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  vertical-align: 1px;
  color: var(--bg);
}

.pub-title {
  margin: 0 0 6px;
  font-family: var(--serif);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: -0.005em;
  color: var(--ink);
}

.pub-title a { color: inherit; text-decoration: none; }

.pub-title a:hover { color: var(--link); }

.authors {
  margin: 0 0 6px;
  font-size: 0.95rem;
  line-height: 1.55;
}

.me { font-weight: 700; color: var(--ink); }

.tldr {
  margin: 0 0 12px;
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--muted);
}

.pub-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
}

.chip {
  display: inline-flex;
  align-items: center;
  padding: 5px 11px;
  border: 1px solid var(--rule);
  border-radius: 7px;
  background: var(--surface);
  font: 600 0.8rem/1.2 var(--sans);
  letter-spacing: 0.02em;
  color: var(--ink-2);
  text-decoration: none;
  cursor: pointer;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.chip:hover,
.chip[aria-expanded="true"] {
  border-color: currentColor;
  color: var(--link);
}

.bib { position: relative; margin-top: 12px; }

.bib pre {
  margin: 0;
  padding: 14px 16px;
  overflow-x: auto;
  border: 1px solid var(--rule);
  border-radius: 10px;
  background: var(--surface);
  font: 0.78rem/1.6 var(--mono);
  color: var(--ink-2);
}

.copy {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 3px 9px;
  border: 1px solid var(--rule);
  border-radius: 6px;
  background: var(--bg);
  font: 600 0.72rem/1.4 var(--sans);
  color: var(--muted);
  cursor: pointer;
}

.copy:hover { color: var(--ink); }

/* ---------- Footer ---------- */

.footer {
  max-width: var(--maxw);
  margin: 80px auto 0;
  padding: 0 var(--pad) 44px;
  font-size: 0.85rem;
  color: var(--muted);
}

.footer p {
  margin: 0;
  padding-top: 22px;
  border-top: 1px solid var(--rule);
}

/* ---------- Motion ---------- */

@media (prefers-reduced-motion: no-preference) {
  html { scroll-behavior: smooth; }

  .portrait,
  .intro > * { animation: rise 0.8s cubic-bezier(0.2, 0.7, 0.2, 1) both; }

  .intro > :nth-child(1) { animation-delay: 0.08s; }
  .intro > :nth-child(2) { animation-delay: 0.14s; }
  .intro > :nth-child(3) { animation-delay: 0.2s; }
  .intro > :nth-child(4) { animation-delay: 0.26s; }
  .intro > :nth-child(5) { animation-delay: 0.32s; }
}

@keyframes rise {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: none; }
}

/* ---------- Small screens ---------- */

@media (max-width: 760px) {
  :root { --gap: 16px; --pad: 18px; }

  /* minmax(0, 1fr), not 1fr: a bare 1fr track grows to the 720px thumbnails' intrinsic width */
  .hero { grid-template-columns: minmax(0, 1fr); gap: 22px; padding-top: 36px; }
  .portrait { width: 136px; border-radius: 14px; }
  .intro h1 { margin-top: 0; }

  .block { margin-top: 52px; }
  h2 { font-size: 1.55rem; }

  .timeline li { grid-template-columns: 4.6em minmax(0, 1fr); gap: 14px; }
  .timeline time { text-align: left; }
  .timeline.exp li { grid-template-columns: minmax(0, 1fr); gap: 2px; }

  .pub { grid-template-columns: minmax(0, 1fr); gap: 14px; margin: 0 -14px; padding: 14px; }
  .pub-thumb { aspect-ratio: 2 / 1; }
}

@media (max-width: 440px) {
  body { font-size: 16px; }
  .topbar-right { gap: 14px; }
  .topbar nav { gap: 16px; }
  .topbar nav a { font-size: 0.88rem; }
}