/* ===========
   Sijie (Skyler) Han — GitHub Pages site
   Clean researcher style with subtle “lab notebook” vibes.
   =========== */

:root{
  --bg: #f6fbf7;
  --bg2: #ecf7f0;
  --card: rgba(24,88,62,0.06);
  --card2: rgba(24,88,62,0.10);
  --text: rgba(12,32,22,0.92);
  --muted: rgba(12,32,22,0.68);
  --faint: rgba(12,32,22,0.52);
  --border: rgba(24,88,62,0.18);
  --accent: #2f8f5b;
  --accent2: #4fbf85;
  --shadow: 0 18px 48px rgba(8,24,16,0.10);
  --radius: 16px;
  --radius-sm: 10px;
  --maxw: 980px;

  --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
}

html, body{ height: 100%; }

body{
  margin: 0;
  font-family: var(--sans);
  color: var(--text);
  background: linear-gradient(180deg, var(--bg), var(--bg2));
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

body.theme-light{
  --bg: #f6fbf7;
  --bg2: #ecf7f0;
  --card: rgba(24,88,62,0.06);
  --card2: rgba(24,88,62,0.10);
  --text: rgba(12,32,22,0.92);
  --muted: rgba(12,32,22,0.68);
  --faint: rgba(12,32,22,0.52);
  --border: rgba(24,88,62,0.18);
  --shadow: 0 18px 48px rgba(8,24,16,0.10);
}

a{ color: inherit; text-decoration: none; }
a:hover{ text-decoration: underline; text-decoration-thickness: 2px; text-underline-offset: 3px; }

.container{
  width: min(100% - 32px, var(--maxw));
  margin-inline: auto;
}

.mono{ font-family: var(--mono); }

.skip-link{
  position: absolute;
  top: -200px; left: 12px;
  padding: 10px 12px;
  background: var(--card2);
  border: 1px solid var(--border);
  border-radius: 10px;
  z-index: 9999;
}
.skip-link:focus{ top: 12px; }

/* top progress */
#top-progress{
  position: fixed;
  left: 0; top: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  z-index: 9999;
}

/* Header / nav */
.site-header{
  position: sticky;
  top: 0;
  z-index: 2000;
  backdrop-filter: blur(12px);
  background: rgba(246,251,247,0.92);
  border-bottom: 1px solid var(--border);
}
body.theme-light .site-header{
  background: rgba(246,251,247,0.92);
  border-bottom: 1px solid var(--border);
}

.nav{
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 0;
  gap: 14px;
}

.brand{
  display: inline-flex;
  gap: 10px;
  align-items: center;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.brand__mark{
  width: 12px; height: 12px;
  border-radius: 999px;
  background: linear-gradient(120deg, var(--accent), var(--accent2));
  box-shadow: 0 0 0 6px rgba(47,143,91,0.12);
}

.nav__links{
  display: flex;
  align-items: center;
  gap: 14px;
}
.nav__link{
  font-size: 0.95rem;
  color: var(--muted);
  padding: 8px 10px;
  border-radius: 10px;
}
.nav__link:hover{
  background: rgba(24,88,62,0.08);
  text-decoration: none;
  color: var(--text);
}
.nav__link.is-active{
  color: var(--text);
  background: rgba(47,143,91,0.12);
  border: 1px solid rgba(47,143,91,0.25);
}
body.theme-light .nav__link:hover{ background: rgba(24,88,62,0.08); }

.nav__link--pill{
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.06);
}

.nav__toggle{
  display: none;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.06);
  border-radius: 12px;
  padding: 10px 10px;
}
.nav__toggle span{
  display: block;
  width: 18px; height: 2px;
  background: var(--text);
  margin: 4px 0;
  border-radius: 2px;
  opacity: 0.9;
}

.theme-toggle{
  border: 1px solid var(--border);
  background: rgba(255,255,255,0.04);
  border-radius: 12px;
  padding: 8px 10px;
  display: inline-flex;
  gap: 8px;
  align-items: center;
  cursor: pointer;
  color: var(--muted);
}
.theme-toggle:hover{
  background: rgba(255,255,255,0.07);
  color: var(--text);
}
body.theme-light .theme-toggle:hover{ background: rgba(0,0,0,0.06); }
.theme-toggle__icon{ font-family: var(--mono); }

/* Hero */
.hero{
  position: relative;
  padding: 64px 0 32px;
}
.hero__bg{ display: none; }
.hero__grid{
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 26px;
  align-items: start;
}

.kicker{
  margin: 0 0 8px 0;
  color: var(--muted);
  font-weight: 600;
  letter-spacing: 0.02em;
  font-size: 0.95rem;
}
.hero__title{
  margin: 0;
  font-size: clamp(2.1rem, 4vw, 3.2rem);
  letter-spacing: -0.03em;
  line-height: 1.12;
}
.hero__subtitle{
  margin: 10px 0 18px 0;
  color: var(--muted);
  font-size: 1.02rem;
}
.hero__lede{
  margin: 0 0 18px 0;
  color: var(--text);
  max-width: 60ch;
}
.hero__lede a,
.section__sub a{
  color: var(--text);
}

.link-underscore{
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
  text-decoration-color: rgba(47,143,91,0.45);
}
.link-underscore:hover{
  text-decoration-color: rgba(47,143,91,0.75);
}
.hero__cta{
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin: 18px 0 16px;
}
.hero__meta{
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 10px 0 6px;
}
.hero__links{
  display: grid;
  gap: 8px;
  margin-top: 14px;
}

.icon-link{
  display: inline-flex;
  gap: 10px;
  align-items: center;
  color: var(--muted);
}
.icon-link__icon{
  width: 22px; height: 22px;
  display: inline-grid;
  place-items: center;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: rgba(24,88,62,0.06);
  font-family: var(--mono);
  font-size: 0.9rem;
}
.icon-link:hover{
  color: var(--text);
  text-decoration: none;
}
.icon-link:hover .icon-link__icon{
  background: rgba(24,88,62,0.10);
}

.btn{
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 11px 14px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.06);
  color: var(--text);
  font-weight: 600;
  cursor: pointer;
  text-decoration: none !important;
}
.btn:hover{
  background: rgba(24,88,62,0.10);
}
body.theme-light .btn:hover{ background: rgba(24,88,62,0.10); }

.btn--primary{
  border: 1px solid rgba(47,143,91,0.35);
  background: rgba(47,143,91,0.18);
}
.btn--primary:hover{
  border-color: rgba(47,143,91,0.55);
  background: rgba(47,143,91,0.24);
}
.btn--ghost{
  background: rgba(24,88,62,0.04);
}
.btn--sm{ padding: 9px 12px; border-radius: 12px; font-size: 0.95rem; }

.chip{
  display: inline-flex;
  padding: 7px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.06);
  color: var(--muted);
  font-size: 0.92rem;
}
.chip--sm{ font-size: 0.86rem; padding: 6px 10px; }

.pill-row{ display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
.pill{
  padding: 7px 10px;
  border-radius: 999px;
  border: 1px dashed rgba(124,92,255,0.45);
  background: rgba(124,92,255,0.10);
  color: var(--text);
  font-size: 0.92rem;
}
.pill--sm{ font-size: 0.86rem; padding: 6px 10px; }

/* Right hero panel */
.hero__panel{
  position: sticky;
  top: 84px;
  display: grid;
  gap: 14px;
  align-items: start;
}

.hero__photo{
  width: 100%;
  display: block;
  border-radius: 14px;
  object-fit: cover;
  aspect-ratio: 4 / 5;
}
.hero__photo--simple{
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.03);
  box-shadow: var(--shadow);
}

.terminal{
  border: 1px solid var(--border);
  background: rgba(0,0,0,0.22);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}
body.theme-light .terminal{ background: rgba(255,255,255,0.55); }

.terminal__bar{
  display: flex;
  gap: 8px;
  padding: 12px 14px;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  background: rgba(255,255,255,0.03);
}
body.theme-light .terminal__bar{ border-bottom: 1px solid rgba(0,0,0,0.08); }
.terminal__bar span{
  width: 10px; height: 10px;
  border-radius: 99px;
  background: rgba(255,255,255,0.20);
}
.terminal__body{
  padding: 14px 14px 16px;
  font-family: var(--mono);
  font-size: 0.92rem;
  color: var(--text);
}
.terminal__prompt{ color: rgba(53,215,255,0.9); }
.terminal__out{ color: var(--muted); margin-top: -8px; margin-bottom: 12px; }

.cards{
  display: grid;
  gap: 12px;
}
.card{
  border: 1px solid var(--border);
  background: rgba(255,255,255,0.04);
  border-radius: var(--radius);
  padding: 14px 14px 12px;
}
.card:hover{
  transform: translateY(-2px);
  transition: transform 180ms ease, background 180ms ease;
  background: rgba(255,255,255,0.06);
}
body.theme-light .card:hover{ background: rgba(0,0,0,0.05); }
.card__title{ margin: 0; font-size: 1.02rem; letter-spacing: -0.01em; }
.card__meta{ margin: 6px 0 8px; color: var(--muted); font-size: 0.92rem; }
.card__desc{ margin: 0 0 10px; color: var(--text); font-size: 0.95rem; }
.card__link{ color: rgba(53,215,255,0.95); font-weight: 700; }

/* Sections */
.section{
  padding: 44px 0;
}
.section__header{
  margin-bottom: 18px;
}
.section__header h2{
  margin: 0;
  font-size: 1.55rem;
  letter-spacing: -0.02em;
}
.section__sub{
  margin: 8px 0 0;
  color: var(--muted);
  max-width: 70ch;
}

.grid{
  display: grid;
  gap: 16px;
}
.grid.two{ grid-template-columns: 1.2fr 0.8fr; }
.grid.three{ grid-template-columns: repeat(3, 1fr); }

.prose p{ margin: 0 0 12px; color: var(--text); }
.muted{ color: var(--muted); }

.sidebox{
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: rgba(255,255,255,0.04);
  padding: 16px;
}
.sidebox h3{ margin: 0 0 10px; font-size: 1.05rem; }
.sidebox__hr{
  height: 1px;
  background: rgba(255,255,255,0.10);
  margin: 14px 0;
}
body.theme-light .sidebox__hr{ background: rgba(0,0,0,0.10); }
.clean{ margin: 0; padding-left: 18px; }
.clean li{ margin: 6px 0; color: var(--text); }

.chips{ display: flex; flex-wrap: wrap; gap: 8px; }

/* Features */
.feature{
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: rgba(255,255,255,0.04);
  padding: 16px;
}
.feature h3{ margin: 0 0 8px; font-size: 1.05rem; }
.feature p{ margin: 0; color: var(--muted); }

/* Callout */
.callout{
  margin-top: 18px;
  border: 1px solid rgba(124,92,255,0.35);
  background: linear-gradient(90deg, rgba(124,92,255,0.14), rgba(53,215,255,0.10));
  border-radius: var(--radius);
  padding: 14px;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 14px;
  align-items: center;
}
.callout__icon{
  width: 36px; height: 36px;
  border-radius: 12px;
  background: rgba(255,255,255,0.08);
  display: grid;
  place-items: center;
  font-size: 1.1rem;
}
.callout__title{
  margin: 0;
  font-weight: 800;
}
.callout__body p{ margin: 0; color: var(--muted); }
.callout__body .callout__title{ color: var(--text); }

/* Publications */
.pubs{ display: grid; gap: 12px; }
.pub{
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: 14px;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.04);
  border-radius: var(--radius);
  padding: 14px;
}
.pub__year{
  font-family: var(--mono);
  color: var(--accent);
  font-weight: 700;
}
.pub__cite{ margin: 0; color: var(--text); }
.pub__links{ margin-top: 8px; display: flex; flex-wrap: wrap; gap: 10px; color: var(--muted); }
.pub__links a{
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 6px 10px;
  text-decoration: none;
  color: var(--accent);
}
.pub__links a:hover{ background: rgba(24,88,62,0.08); }

/* Projects */
.project__head{
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px;
}
.project__title{ margin: 0; }
.project__time{ margin: 0; color: var(--muted); font-family: var(--mono); font-size: 0.9rem; }
.project__desc{ margin: 10px 0 0; color: var(--text); }

.card--flat{ box-shadow: none; }

/* Timeline */
.timeline{
  position: relative;
  margin-top: 8px;
  padding-left: 18px;
}
.timeline::before{
  content: "";
  position: absolute;
  left: 6px; top: 0; bottom: 0;
  width: 2px;
  background: rgba(24,88,62,0.18);
}
body.theme-light .timeline::before{ background: rgba(24,88,62,0.18); }

.tl-item{
  position: relative;
  padding: 0 0 16px 0;
}
.tl-dot{
  position: absolute;
  left: -1px; top: 12px;
  width: 14px; height: 14px;
  border-radius: 999px;
  background: linear-gradient(120deg, var(--accent), var(--accent2));
  box-shadow: 0 0 0 6px rgba(47,143,91,0.12);
}
.tl-content{
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.05);
  border-radius: var(--radius);
  padding: 14px;
  margin-left: 16px;
}
.tl-top{ display: grid; gap: 4px; }
.tl-title{ margin: 0; font-size: 1.05rem; }
.tl-meta{ margin: 0; color: var(--muted); font-family: var(--mono); font-size: 0.9rem; }
.tl-list{ margin: 10px 0 0; padding-left: 18px; color: var(--text); }
.tl-list li{ margin: 6px 0; }

.tl-head{
  display: flex;
  align-items: center;
  gap: 12px;
}

.tl-logo{
  width: 40px;
  height: 40px;
  border-radius: 10px;
  border: 1px solid rgba(47,143,91,0.35);
  background: var(--accent);
  display: grid;
  place-items: center;
  font-family: var(--mono);
  font-weight: 700;
  font-size: 0.85rem;
  color: #ffffff;
}

/* CV box */
.cvbox{
  border: 1px solid rgba(53,215,255,0.30);
  background: linear-gradient(90deg, rgba(53,215,255,0.10), rgba(124,92,255,0.10));
  border-radius: var(--radius);
  padding: 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: 16px;
}
.cvbox__title{ margin: 0; font-weight: 900; letter-spacing: -0.02em; }

.kv{
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: 10px 14px;
}
.kv__k{ color: var(--muted); font-family: var(--mono); font-size: 0.9rem; }
.kv__v{ color: var(--text); }

/* Contact */
.contact{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
}
.contact__card{
  border: 1px solid var(--border);
  background: rgba(255,255,255,0.04);
  border-radius: var(--radius);
  padding: 16px;
}
.contact__title{ margin: 0 0 8px; font-weight: 800; }
.contact__value{ margin: 0 0 12px; color: var(--text); }
.contact__actions{ display: flex; gap: 10px; flex-wrap: wrap; }
.contact__links{ display: flex; gap: 12px; flex-wrap: wrap; }
.contact__links a{
  color: rgba(53,215,255,0.95);
  font-weight: 700;
}

/* Footer */
.site-footer{
  border-top: 1px solid var(--border);
  padding: 26px 0;
  background: rgba(24,88,62,0.04);
}
body.theme-light .site-footer{
  border-top: 1px solid var(--border);
  background: rgba(24,88,62,0.04);
}
.footer__grid{
  display: grid;
  gap: 8px;
}

/* Back to top */
.to-top{
  position: fixed;
  right: 16px;
  bottom: 16px;
  width: 44px; height: 44px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.08);
  color: var(--text);
  cursor: pointer;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 160ms ease, transform 160ms ease;
}
.to-top.show{ opacity: 1; transform: translateY(0); }
.to-top:hover{ background: rgba(24,88,62,0.12); }

/* Toast */
.toast{
  position: fixed;
  left: 50%;
  transform: translateX(-50%);
  bottom: 18px;
  padding: 10px 12px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(24,88,62,0.92);
  color: #ffffff;
  font-family: var(--mono);
  font-size: 0.9rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 160ms ease, transform 160ms ease;
}
body.theme-light .toast{ background: rgba(24,88,62,0.92); color: #ffffff; }
.toast.show{
  opacity: 1;
  transform: translateX(-50%) translateY(-6px);
}

/* Responsive */
@media (max-width: 980px){
  .hero__grid{ grid-template-columns: 1fr; }
  .hero__panel{ position: relative; top: auto; }
  .grid.two{ grid-template-columns: 1fr; }
  .grid.three{ grid-template-columns: 1fr; }
  .contact{ grid-template-columns: 1fr; }
}

@media (max-width: 760px){
  .nav__toggle{ display: inline-block; }
  .nav__links{
    position: absolute;
    right: 16px;
    top: 62px;
    width: min(92vw, 420px);
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: rgba(246,251,247,0.98);
    backdrop-filter: blur(12px);
    box-shadow: var(--shadow);
  }
  body.theme-light .nav__links{ background: rgba(246,251,247,0.98); }
  .nav__links.open{ display: flex; }
  .nav__link{ padding: 10px 12px; }
  .theme-toggle{ justify-content: center; }
  .hero{ padding-top: 62px; }
  .pub{ grid-template-columns: 1fr; }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce){
  *{ scroll-behavior: auto !important; }
  .card:hover{ transform: none; }
  .to-top{ transition: none; }
  .toast{ transition: none; }
}