@charset "UTF-8";

/* =========================================================================
   Zizhou Huang — personal site
   One stylesheet. No framework. Light/dark follows the OS.
   ========================================================================= */

/* ---------- Design tokens ------------------------------------------------ */

:root {
  color-scheme: light dark;

  /* Type */
  --font-serif: "Source Serif 4", Charter, "Iowan Old Style", Georgia, serif;
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", monospace;

  /* Scale */
  --step--1: 0.875rem;
  --step-0: 1.0rem;
  --step-1: 1.125rem;
  --step-2: clamp(1.25rem, 0.4vw + 1.15rem, 1.4rem);
  --step-3: clamp(1.5rem, 1vw + 1.25rem, 1.9rem);
  --step-4: clamp(2rem, 2.2vw + 1.4rem, 2.9rem);

  /* Rhythm */
  --measure: 68ch;
  --page: 62rem;
  --gutter: clamp(1.25rem, 4vw, 3rem);
  --section-gap: clamp(3rem, 6vw, 4.75rem);
  --radius: 6px;

  /* Light palette */
  --bg: #ffffff;
  --surface: #f7f7f5;
  --media-bg: #ffffff;
  --ink: #16181d;
  --ink-muted: #5c6270;
  --ink-faint: #868c99;
  --rule: #e3e4e8;
  --rule-strong: #cfd1d8;
  --accent: #1f4f8f;
  --accent-soft: rgba(31, 79, 143, 0.09);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1115;
    --surface: #171a20;
    --media-bg: #ffffff;
    --ink: #e7e9ee;
    --ink-muted: #a3aab8;
    --ink-faint: #7f8797;
    --rule: #262a33;
    --rule-strong: #363b46;
    --accent: #8fb6ee;
    --accent-soft: rgba(143, 182, 238, 0.14);
  }
}

/* ---------- Reset -------------------------------------------------------- */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: var(--step-0);
  line-height: 1.62;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

h1,
h2,
h3,
h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  line-height: 1.2;
  margin: 0;
  letter-spacing: -0.01em;
}

p {
  margin: 0 0 1em;
  max-width: var(--measure);
}

ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

a {
  color: var(--accent);
  text-decoration: none;
  text-underline-offset: 0.2em;
  text-decoration-thickness: 1px;
  transition: color 0.15s ease, border-color 0.15s ease,
    background-color 0.15s ease;
}

a:hover {
  text-decoration: underline;
}

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

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  * {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* ---------- Layout primitives ------------------------------------------- */

.wrap {
  width: 100%;
  max-width: var(--page);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--bg);
  color: var(--ink);
  padding: 0.6rem 1rem;
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius);
  z-index: 100;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
}

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

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--rule);
}

.site-header__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.5rem 1.5rem;
  padding-block: 0.9rem;
}

.wordmark {
  font-family: var(--font-serif);
  font-size: var(--step-1);
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--ink);
}

.wordmark:hover {
  text-decoration: none;
  color: var(--accent);
}

.site-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1.5rem;
  font-size: var(--step--1);
}

.site-nav a {
  color: var(--ink-muted);
  padding-block: 0.15rem;
  border-bottom: 1px solid transparent;
}

.site-nav a:hover,
.site-nav a[aria-current="page"] {
  color: var(--ink);
  border-bottom-color: var(--accent);
  text-decoration: none;
}

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

main {
  padding-block: clamp(2.5rem, 6vw, 4.5rem) 0;
}

.section {
  margin-block-end: var(--section-gap);
  scroll-margin-top: 5rem;
}

.section__title {
  font-size: var(--step-2);
  font-weight: 600;
  padding-bottom: 0.5rem;
  margin-bottom: 1.75rem;
  border-bottom: 1px solid var(--rule);
  letter-spacing: 0;
}

.lede {
  font-size: var(--step-1);
  color: var(--ink-muted);
}

/* ---------- Hero / intro ------------------------------------------------- */

.intro {
  display: grid;
  grid-template-columns: 190px minmax(0, 1fr);
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
  margin-block-end: var(--section-gap);
}

.intro__portrait {
  width: 100%;
  aspect-ratio: 4 / 5;
  object-fit: cover;
  border-radius: var(--radius);
  border: 1px solid var(--rule);
  filter: saturate(0.96);
}

.intro__name {
  font-size: var(--step-4);
  margin-bottom: 0.35rem;
}

.intro__role {
  font-size: var(--step-1);
  color: var(--ink-muted);
  margin-bottom: 1.25rem;
}

.intro__bio p:last-child {
  margin-bottom: 0;
}

.intro__meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 1.5rem;
  margin-top: 1.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--rule);
  font-size: var(--step--1);
  color: var(--ink-muted);
}

.intro__meta a {
  color: var(--ink-muted);
  border-bottom: 1px solid var(--rule-strong);
}

.intro__meta a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
  text-decoration: none;
}

.affiliations {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

.affiliations img {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  object-fit: cover;
  background: var(--media-bg);
  border: 1px solid var(--rule);
}

/* Icon links (GitHub, Scholar) */

.icon-links {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.icon-links .icon-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border: 1px solid var(--rule-strong);
  border-radius: 50%;
  color: var(--ink-muted);
}

.icon-links .icon-link svg {
  width: 16px;
  height: 16px;
  display: block;
  fill: currentColor;
}

.icon-links .icon-link:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  text-decoration: none;
}

@media (max-width: 640px) {
  .intro {
    grid-template-columns: minmax(0, 1fr);
  }
  .intro__portrait {
    width: 148px;
    aspect-ratio: 1 / 1;
  }
}

/* ---------- News --------------------------------------------------------- */

.news {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 22rem), 1fr));
  gap: 0 clamp(1.5rem, 4vw, 3rem);
}

.news__item {
  display: grid;
  grid-template-columns: 6.5rem minmax(0, 1fr);
  gap: 0 1rem;
  padding-block: 0.7rem;
  border-bottom: 1px solid var(--rule);
  font-size: var(--step--1);
}

.news__date {
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  padding-top: 0.05em;
}

.news__item p {
  margin: 0;
  max-width: none;
}

@media (max-width: 460px) {
  .news__item {
    grid-template-columns: minmax(0, 1fr);
    gap: 0.15rem;
  }
}

/* ---------- Entry list (publications, projects, teaching) ---------------- */

.entries {
  display: grid;
  gap: clamp(1.75rem, 3vw, 2.5rem);
}

.entry {
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr);
  gap: clamp(1rem, 3vw, 2rem);
  align-items: start;
}

.entry__media {
  background: var(--media-bg);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 92px;
  padding: 0.5rem;
}

.entry__media img {
  width: 100%;
  object-fit: contain;
  transition: transform 0.3s ease;
}

a.entry__media:hover img {
  transform: scale(1.02);
}

.entry__title {
  font-size: var(--step-1);
  font-weight: 600;
  line-height: 1.35;
  margin-bottom: 0.3rem;
}

.entry__title a {
  color: var(--ink);
}

.entry__title a:hover {
  color: var(--accent);
  text-decoration: none;
}

.entry__authors {
  font-size: var(--step--1);
  color: var(--ink-muted);
  margin-bottom: 0.2rem;
  max-width: var(--measure);
}

.entry__authors .me {
  color: var(--ink);
  font-weight: 600;
}

.entry__venue {
  font-size: var(--step--1);
  color: var(--ink-faint);
  font-style: italic;
  margin-bottom: 0.75rem;
}

.entry__note {
  font-size: var(--step--1);
  color: var(--ink-muted);
  margin-bottom: 0.75rem;
  max-width: var(--measure);
}

@media (max-width: 640px) {
  .entry {
    grid-template-columns: minmax(0, 1fr);
  }
}

/* ---------- Link chips --------------------------------------------------- */

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.chip {
  display: inline-block;
  font-size: 0.8125rem;
  line-height: 1.4;
  padding: 0.22rem 0.65rem;
  border: 1px solid var(--rule-strong);
  border-radius: 999px;
  color: var(--ink-muted);
  white-space: nowrap;
}

.chip:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  text-decoration: none;
}

/* ---------- Teaching ----------------------------------------------------- */

.teaching__group + .teaching__group {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--rule);
}

.teaching__where {
  font-family: var(--font-serif);
  font-size: var(--step-1);
  font-weight: 600;
  margin-bottom: 0.35rem;
}

.teaching__list {
  display: grid;
  gap: 0.15rem;
  font-size: var(--step--1);
  color: var(--ink-muted);
}

.teaching__list span {
  font-variant-numeric: tabular-nums;
  color: var(--ink-faint);
  margin-right: 0.6rem;
}

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

.site-footer {
  border-top: 1px solid var(--rule);
  margin-top: var(--section-gap);
  padding-block: 2rem 2.5rem;
  font-size: var(--step--1);
  color: var(--ink-faint);
}

.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  justify-content: space-between;
}

.site-footer a {
  color: var(--ink-faint);
  border-bottom: 1px solid var(--rule-strong);
}

.site-footer a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
  text-decoration: none;
}

/* =========================================================================
   Paper pages
   ========================================================================= */

.paper {
  max-width: 52rem;
  margin-inline: auto;
}

.paper__header {
  text-align: center;
  padding-block-end: 2rem;
  border-bottom: 1px solid var(--rule);
  margin-block-end: clamp(2rem, 5vw, 3rem);
}

.paper__title {
  font-size: var(--step-4);
  margin-bottom: 1rem;
  text-wrap: balance;
}

.paper__authors {
  font-size: var(--step-0);
  color: var(--ink-muted);
  margin: 0 auto 0.5rem;
  max-width: 48rem;
}

.paper__authors a {
  color: var(--ink);
}

.paper__authors sup {
  color: var(--ink-faint);
  font-size: 0.7em;
}

.paper__affiliation,
.paper__venue {
  font-size: var(--step--1);
  color: var(--ink-faint);
  margin: 0 auto 0.4rem;
  max-width: 48rem;
}

.paper__venue {
  font-style: italic;
  margin-bottom: 1.5rem;
}

.paper__header .chips {
  justify-content: center;
}

.paper__header .chip {
  padding: 0.35rem 0.9rem;
  font-size: var(--step--1);
}

.paper section {
  margin-block-end: clamp(2.5rem, 5vw, 3.5rem);
}

.paper h2 {
  font-size: var(--step-3);
  margin-bottom: 1rem;
}

.paper h3 {
  font-size: var(--step-1);
  margin-bottom: 0.5rem;
  color: var(--ink);
}

.paper p {
  max-width: none;
  color: var(--ink);
}

.paper .prose {
  max-width: var(--measure);
  margin-inline: auto;
}

/* Figures */

figure {
  margin: 0 0 1.5rem;
}

figure img,
figure video {
  width: 100%;
  border-radius: var(--radius);
  border: 1px solid var(--rule);
  background: var(--media-bg);
}

figure img + img {
  margin-top: 1rem;
}

figcaption {
  margin-top: 0.6rem;
  font-size: var(--step--1);
  color: var(--ink-muted);
  text-align: center;
  max-width: var(--measure);
  margin-inline: auto;
}

.figure-pair {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 17rem), 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.figure-pair figure {
  margin-bottom: 0;
}

.figure-pair figcaption {
  text-align: center;
}

.figure--narrow img {
  max-width: 400px;
  margin-inline: auto;
}

/* Horizontal carousel — CSS only, scroll-snap + anchor pagination.
   Slides are height-capped so a whole figure fits a 1080p viewport. */

.carousel {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 100%;
  overflow-x: auto;
  overscroll-behavior-x: contain;
  scroll-snap-type: x mandatory;
  scroll-behavior: smooth;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--media-bg);
  scrollbar-color: var(--rule-strong) transparent;
}

.carousel__item {
  scroll-snap-align: start;
  min-width: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.35rem;
}

.carousel img {
  width: auto;
  max-width: 100%;
  max-height: min(560px, 58vh);
  border: 0;
  border-radius: 0;
  margin-top: 0;
}

/* --auto: slides sized to their content, so neighbouring panels stay visible */

.carousel--auto {
  grid-auto-columns: max-content;
  gap: 0.5rem;
  padding: 0.35rem;
}

.carousel--auto .carousel__item {
  padding: 0;
}

.carousel--auto img {
  max-height: min(430px, 46vh);
}

.carousel::-webkit-scrollbar {
  height: 8px;
}

.carousel::-webkit-scrollbar-thumb {
  background: var(--rule-strong);
  border-radius: 999px;
}

.carousel__nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
  margin-top: 0.6rem;
  font-size: var(--step--1);
  color: var(--ink-faint);
}

.carousel__nav a {
  min-width: 2.1rem;
  text-align: center;
  padding: 0.15rem 0.55rem;
  border: 1px solid var(--rule-strong);
  border-radius: 999px;
  color: var(--ink-muted);
  font-size: 0.8125rem;
}

.carousel__nav a:hover,
.carousel__nav a:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  text-decoration: none;
}

.carousel__hint {
  margin-left: auto;
}

@media (max-width: 560px) {
  .carousel__hint {
    margin-left: 0;
  }
}

.figure-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.figure-grid img + img,
.figure-grid figure {
  margin-top: 0;
  margin-bottom: 0;
}

@media (max-width: 560px) {
  .figure-grid {
    grid-template-columns: minmax(0, 1fr);
  }
}

.subhead {
  font-size: var(--step--1);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faint);
  font-family: var(--font-sans);
  font-weight: 600;
  margin-bottom: 0.75rem;
  margin-top: 2rem;
}

/* Citation block */

.citation {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.1rem 1.25rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  line-height: 1.6;
  color: var(--ink-muted);
  white-space: pre;
  margin: 0;
}

/* Related work list */

.related {
  display: grid;
  gap: 1rem;
}

.related__item {
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--rule);
  font-size: var(--step--1);
}

.related__item:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.related__item strong {
  display: block;
  font-family: var(--font-serif);
  font-size: var(--step-0);
  font-weight: 600;
  color: var(--ink);
}

.related__item span {
  color: var(--ink-muted);
}

.related__item em {
  color: var(--ink-faint);
}

/* Back link on paper pages */

.backlink {
  display: inline-block;
  font-size: var(--step--1);
  color: var(--ink-muted);
  margin-bottom: 2rem;
}

.backlink:hover {
  color: var(--accent);
  text-decoration: none;
}

@media print {
  .site-header,
  .site-footer,
  .backlink {
    display: none;
  }
  body {
    color: #000;
    background: #fff;
  }
}