/* ==========================================================================
   Yuan Chen — personal site
   Warm academic + clean modern blend
   ========================================================================== */

:root {
  --cream: #ffffff;
  --cream-alt: #f2f5f9;
  --card: #ffffff;
  --ink: #1c2b3a;
  --ink-soft: #5b7184;
  --rust: #205ea6;
  --rust-light: #3f80c9;
  --gold: #6f93bd;
  --border: #d8e2ee;
  --shadow: 0 2px 14px rgba(28, 43, 58, 0.08);
  --max-width: 880px;
  --nav-height: 72px;
  color-scheme: light;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  overflow-x: hidden;
}

body {
  margin: 0;
  background: var(--cream);
  color: var(--ink);
  font-family: "Optima", "STFangSong", -apple-system, BlinkMacSystemFont, "PingFang SC", "Segoe UI", sans-serif;
  font-size: 16.5px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  transition: background 0.25s ease, color 0.25s ease;
  text-align: justify;
  text-justify: inter-word;
  overflow-wrap: break-word;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  font-family: "Optima", "STFangSong", -apple-system, BlinkMacSystemFont, "PingFang SC", "Segoe UI", sans-serif;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.25;
  margin: 0 0 0.5em;
}

h1 { font-size: 2.5rem; font-weight: 500; }
h2 { font-size: 1.5rem; letter-spacing: 0.01em; -webkit-text-stroke: 0.3px currentColor; }
h3 { font-size: 1.15rem; -webkit-text-stroke: 0.3px currentColor; }

/* Optima's bold face has very low weight contrast — add a hairline
   text-stroke so bold/emphasis text actually reads as bold. */
strong, b, .brand {
  -webkit-text-stroke: 0.3px currentColor;
}

p { margin: 0 0 1.1em; }

a {
  color: var(--rust);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.15s ease, color 0.15s ease;
}
a:hover { border-bottom-color: var(--rust); }

ul { padding-left: 1.3em; }
li { margin-bottom: 0.45em; }

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 28px;
}

/* ---------------- Nav ---------------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.92);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}

.site-nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--nav-height);
}

.brand {
  font-family: "Optima", "STFangSong", -apple-system, BlinkMacSystemFont, "PingFang SC", "Segoe UI", sans-serif;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--ink);
  border-bottom: none;
  white-space: nowrap;
}
.brand:hover { color: var(--rust); border-bottom: none; }
.brand .surname { color: var(--rust); }
.brand .cn-name {
  font-family: "Noto Serif SC", cursive, sans-serif;
  font-weight: 400;
  font-size: 0.9em;
  margin-left: 2px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 30px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links a {
  color: var(--ink-soft);
  font-size: 0.93rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  border-bottom: 2px solid transparent;
  padding-bottom: 4px;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--rust);
  border-bottom-color: var(--rust);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.4rem;
  color: var(--ink);
  cursor: pointer;
  padding: 10px;
  margin: -10px;
  -webkit-tap-highlight-color: transparent;
}

/* ---------------- Hero / page header ---------------- */
.page-header {
  padding: 56px 0 28px;
}
.page-header .kicker {
  text-transform: uppercase;
  letter-spacing: 0.18em;
  font-size: 0.78rem;
  color: var(--rust-light);
  font-weight: 600;
  margin-bottom: 10px;
}
.page-header p.lede {
  color: var(--ink-soft);
  font-size: 1.05rem;
  max-width: 640px;
}

main { padding-bottom: 70px; }

/* ---------------- Home hero ---------------- */
.hero {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 48px;
  align-items: start;
  padding: 50px 0 10px;
}

/* Grid items default to min-width: auto, which lets unwrapped content
   (e.g. the flex rows below) force the column — and the whole page —
   wider than the viewport on mobile. min-width: 0 lets them shrink
   and wrap normally instead of overflowing. */
.hero-side,
.hero-info {
  min-width: 0;
}

.hero img.avatar {
  display: block;
  width: 180px;
  height: 180px;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  border-radius: 50%;
  border: 4px solid var(--card);
  box-shadow: 0 0 0 3px var(--rust), var(--shadow);
  margin: 0 auto 22px;
}

.info-list {
  list-style: none;
  margin: 0;
  padding: 0;
  font-size: 0.88rem;
  color: var(--ink-soft);
}
.info-list li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 11px 0;
  border-bottom: 1px solid var(--border);
  text-align: justify;
  text-justify: inter-word;
}
.info-list li:last-child { border-bottom: none; }
/* Same min-width: auto fix as above — lets the address/email text
   wrap inside its flex item instead of pushing past the edge. */
.info-list li > span {
  min-width: 0;
}
.info-list .label {
  font-weight: 700;
  color: var(--rust);
}
.info-list .icon {
  width: 15px;
  height: 15px;
  flex-shrink: 0;
  margin-top: 3px;
  color: var(--rust);
}
.info-list a { color: var(--rust); }
.info-list a:hover { color: var(--rust-light); }

.hero-info h1 { margin-bottom: 18px; }
.hero-info p { color: var(--ink); max-width: 660px; }
.hero-info a { font-weight: 500; }
.hero-info .related-label {
  font-weight: 400;
  color: var(--ink);
  margin-bottom: 4px;
}

/* ---------------- Pills / tags ---------------- */
.pill-row {
  display: flex;
  flex-wrap: nowrap;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  gap: 8px;
  margin: 18px 0 8px;
  padding: 4px 2px;
}
.pill {
  display: inline-block;
  flex-shrink: 0;
  white-space: nowrap;
  background: var(--cream-alt);
  border: 1px solid var(--border);
  color: var(--ink);
  border-radius: 6px;
  padding: 6px 12px;
  font-size: 0.82rem;
  font-weight: 500;
  transition: border-color 0.2s ease, background 0.2s ease, color 0.2s ease, transform 0.2s ease;
}
.pill:hover {
  border-color: var(--rust);
  background: rgba(32, 94, 166, 0.08);
  color: var(--rust);
  transform: translateY(-1px);
}

/* ---------------- Icon buttons (social/profile links) ---------------- */
.social-row {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 10px;
  margin: 18px 0 6px;
}
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--rust);
  font-size: 2.15rem;
  line-height: 1;
  border-bottom: none;
  transition: opacity 0.2s ease;
  padding: 5px;
  margin: -5px;
  -webkit-tap-highlight-color: transparent;
}
.icon-btn:hover {
  opacity: 0.7;
  border-bottom: none;
}
.icon-btn .text-glyph {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.9rem;
  height: 1.9rem;
  background: var(--rust);
  color: #fff;
  border-radius: 4px;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.icon-btn .text-glyph i { font-size: 1rem; }
.icon-btn .text-glyph .spiral-icon {
  width: 1.3rem;
  height: 1.3rem;
  display: block;
}

/* ---------------- Section ---------------- */
.section {
  padding: 28px 0 14px;
  border-top: 1px solid var(--border);
}
.section:first-of-type { border-top: none; }
.section-title {
  display: flex;
  align-items: baseline;
  gap: 14px;
  margin-bottom: 22px;
}
.section-title h2 { margin: 0; }
.section-title .count {
  color: var(--ink-soft);
  font-size: 0.85rem;
}

/* ---------------- Publications ---------------- */
.pub-group { margin-bottom: 14px; }
.pub-group h3 {
  color: var(--rust);
  font-size: 0.92rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 10px;
}
.pub-list {
  list-style: disc;
  padding-left: 1.2em;
  margin: 0;
}
.pub-item {
  padding: 0;
  margin-bottom: 10px;
}
.pub-item::marker { color: var(--ink-soft); }
.pub-item:last-child { margin-bottom: 0; }
.pub-item .pub-title {
  font-weight: 400;
  color: var(--ink);
  font-size: 1.08rem;
  line-height: 1.35;
  margin-bottom: 2px;
}
.pub-item .pub-authors {
  color: var(--ink);
  font-size: 0.97rem;
  line-height: 1.35;
  margin-bottom: 2px;
}
.pub-item .pub-venue {
  color: var(--ink-soft);
  font-size: 0.92rem;
  line-height: 1.35;
}
.pub-item .pub-venue em { font-style: italic; }
.pub-item .pub-venue a {
  color: var(--rust);
  font-weight: 600;
  margin-left: 4px;
  white-space: nowrap;
}
.pub-item .pub-venue a:hover { color: var(--rust-light); }

/* ---------------- Timeline (talks) ---------------- */
.timeline-item {
  display: grid;
  grid-template-columns: 190px 1fr;
  gap: 18px;
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
}
.timeline-item:last-child { border-bottom: none; }
.timeline-item .date,
.timeline-item .what {
  min-width: 0;
}
.timeline-item .date {
  color: var(--rust);
  font-size: 0.88rem;
  font-weight: 600;
  white-space: nowrap;
}
.timeline-item .what .conf { font-weight: 600; }
.timeline-item .what .loc { color: var(--ink-soft); font-size: 0.9rem; }

/* ---------------- Footer ---------------- */
footer {
  border-top: 1px solid var(--border);
  padding: 32px 0 46px;
  color: var(--ink-soft);
  font-size: 0.88rem;
}
footer .container {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}
footer .icons {
  display: flex;
  gap: 16px;
}
footer .icons a {
  color: var(--ink-soft);
  border-bottom: none;
  font-size: 0.85rem;
}
footer .icons a:hover { color: var(--rust); }

/* ---------------- Responsive ---------------- */
@media (max-width: 720px) {
  /* Keep justify on phone too, but allow word-internal breaks so
     narrow lines don't get ugly, stretched-out gaps between words. */
  body {
    hyphens: auto;
    -webkit-hyphens: auto;
  }
  .hero { grid-template-columns: 1fr; gap: 30px; padding: 36px 0 6px; }
  .hero img.avatar { width: 150px; height: 150px; }
  .social-row { gap: 6px; }
  .nav-links {
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--cream);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
    padding: 16px 28px 22px;
    display: none;
  }
  .nav-links.open { display: flex; }
  .nav-links a { width: 100%; padding: 10px 0; }
  .nav-toggle { display: inline-flex; }
  .timeline-item { grid-template-columns: 1fr; gap: 4px; }
  h1 { font-size: 2rem; }
}

@media (max-width: 420px) {
  .container { padding: 0 18px; }
}