/* ==========================================================
   Sheng Qu — academic site
   Palette: cool paper ground, ink text, LiDAR teal, signal orange
   Type: Archivo (display) · Source Serif 4 (body) · IBM Plex Mono (meta)
   ========================================================== */

:root {
  --paper:  #F6F8F7;
  --panel:  #EDF1EF;
  --ink:    #101B24;
  --slate:  #45535E;
  --scan:   #0B7C86;   /* point-cloud teal */
  --signal: #C2410C;   /* intensity orange — small doses only */
  --rule:   #D4DCD9;
  --maxw: 1080px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .sweep, .scan-rings { animation: none !important; }
}

body {
  background: var(--paper);
  color: var(--ink);
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 1.06rem;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

.mono { font-family: 'IBM Plex Mono', monospace; }

a { color: var(--scan); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
a:focus-visible { outline: 2px solid var(--signal); outline-offset: 3px; border-radius: 2px; }

/* ---------- nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 10;
  display: flex; justify-content: space-between; align-items: center;
  max-width: var(--maxw); margin: 0 auto;
  padding: 1rem 1.5rem;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(6px);
}
.nav-name {
  font-family: 'Archivo', sans-serif;
  font-weight: 700; font-stretch: 115%;
  letter-spacing: 0.12em; color: var(--ink); font-size: 0.95rem;
}
.nav-links { display: flex; gap: 1.4rem; }
.nav-links a {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.82rem; color: var(--slate);
}
.nav-links a:hover { color: var(--scan); text-decoration: none; }

/* ---------- hero ---------- */
.hero {
  position: relative;
  max-width: var(--maxw); margin: 0 auto;
  padding: 4.5rem 1.5rem 5.5rem;
  overflow: hidden;
}
.hero-scan {
  position: absolute; right: -160px; top: -120px;
  width: 560px; height: 560px;
  opacity: 0.9; pointer-events: none;
}
.sweep { transform-origin: 280px 280px; animation: sweep 14s linear infinite; }
@keyframes sweep { to { transform: rotate(360deg); } }

.hero-inner {
  position: relative;
  display: grid; grid-template-columns: 1fr 280px;
  gap: 3.5rem; align-items: start;
}
.eyebrow {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.8rem; letter-spacing: 0.06em;
  color: var(--scan);
  margin-bottom: 1.2rem;
}
.hero h1 {
  font-family: 'Archivo', sans-serif;
  font-weight: 700; font-stretch: 120%;
  font-size: clamp(2.8rem, 6vw, 4.4rem);
  line-height: 1.02; letter-spacing: -0.015em;
  margin-bottom: 1rem;
}
.hero h1 .cn {
  font-size: 0.38em; font-weight: 400; font-stretch: 100%;
  color: var(--slate); vertical-align: 0.5em; margin-left: 0.4em;
}
.hero-role { font-size: 1.05rem; color: var(--slate); margin-bottom: 1.6rem; }
.hero-seeking {
  color: var(--signal);
  font-family: 'IBM Plex Mono', monospace; font-size: 0.85rem;
}
.hero-bio { max-width: 58ch; margin-bottom: 2rem; }

.hero-actions { display: flex; gap: 0.9rem; }
.btn {
  font-family: 'IBM Plex Mono', monospace; font-size: 0.85rem;
  padding: 0.6rem 1.15rem;
  border: 1.5px solid var(--ink); border-radius: 3px;
  color: var(--ink);
}
.btn:hover { text-decoration: none; background: var(--panel); }
.btn-solid { background: var(--ink); color: var(--paper); }
.btn-solid:hover { background: var(--scan); border-color: var(--scan); }

.hero-photo img {
  width: 100%; height: auto; display: block;
  border-radius: 4px;
  border: 1px solid var(--rule);
}
.hero-photo figcaption {
  font-size: 0.72rem; color: var(--slate);
  margin-top: 0.6rem; text-align: right;
}

/* ---------- sections ---------- */
.section { max-width: var(--maxw); margin: 0 auto; padding: 4.5rem 1.5rem; }
.section-head { margin-bottom: 3rem; max-width: 60ch; }
.section h2 {
  font-family: 'Archivo', sans-serif;
  font-weight: 700; font-stretch: 118%;
  font-size: 2rem; letter-spacing: -0.01em;
  margin-bottom: 0.6rem;
}
.section h2::before {
  content: "◍ ";
  color: var(--scan); font-size: 0.75em;
}
.section-sub { color: var(--slate); font-style: italic; }

.section-alt {
  max-width: none;
  background: var(--panel);
  border-top: 1px solid var(--rule); border-bottom: 1px solid var(--rule);
}
.section-alt > * { max-width: var(--maxw); margin-left: auto; margin-right: auto; }
.section-alt .section-head { margin-bottom: 3rem; }

/* ---------- projects ---------- */
.project {
  display: grid; grid-template-columns: 5fr 6fr;
  gap: 2.5rem; align-items: start;
  padding: 2.5rem 0;
  border-top: 1px solid var(--rule);
}
.project:last-of-type { border-bottom: 1px solid var(--rule); }

.project-media img, .project-media .pipe {
  width: 100%; height: auto; display: block;
  border-radius: 4px; border: 1px solid var(--rule);
  background: #0b0f14;
}
.project-media .pipe { background: var(--paper); padding: 0.5rem 0; }
.project-media-double { display: grid; gap: 0.7rem; }

.meta {
  font-size: 0.76rem; color: var(--slate);
  letter-spacing: 0.01em; line-height: 1.9;
  margin-bottom: 0.9rem;
}
.tag {
  display: inline-block;
  border: 1px solid var(--slate); border-radius: 3px;
  padding: 0.05rem 0.5rem; margin-right: 0.6rem;
  font-size: 0.72rem; letter-spacing: 0.05em;
  text-transform: uppercase;
}
.tag-active { border-color: var(--scan); color: var(--scan); }

.project h3 {
  font-family: 'Archivo', sans-serif;
  font-weight: 600; font-stretch: 112%;
  font-size: 1.45rem; line-height: 1.2;
  margin-bottom: 0.9rem;
}
.project p { margin-bottom: 0.9rem; max-width: 62ch; }
.links { font-size: 0.85rem; }

/* ---------- background ---------- */
.bg-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 3.5rem;
}
.bg-label {
  font-size: 0.78rem; letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--scan); margin-bottom: 1.1rem;
}
.bg-col .bg-label:not(:first-child) { margin-top: 2rem; }

.edu { list-style: none; }
.edu li { margin-bottom: 1.4rem; display: grid; gap: 0.15rem; }
.edu strong { font-family: 'Archivo', sans-serif; font-stretch: 110%; font-weight: 600; }
.edu span { color: var(--slate); font-size: 0.95rem; }
.edu-note { font-size: 0.75rem !important; }

.course-list { list-style: none; }
.course-list li {
  display: flex; justify-content: space-between; gap: 1rem;
  padding: 0.45rem 0; border-bottom: 1px dashed var(--rule);
  font-size: 0.97rem;
}
.course-list .mono { color: var(--slate); font-size: 0.78rem; }

/* ---------- footer ---------- */
.footer { background: var(--ink); color: var(--paper); }
.footer-inner { max-width: var(--maxw); margin: 0 auto; padding: 4rem 1.5rem 3rem; }
.footer-big {
  font-family: 'Archivo', sans-serif;
  font-weight: 600; font-stretch: 112%;
  font-size: clamp(1.3rem, 3vw, 1.8rem); line-height: 1.3;
  max-width: 32ch; margin-bottom: 2rem;
}
.footer a { color: #7BD3DB; }
.footer-links { font-size: 0.85rem; margin-bottom: 2.5rem; }
.footer-fine { font-size: 0.72rem; color: #7d8a94; }

/* ---------- responsive ---------- */
@media (max-width: 860px) {
  .hero-inner { grid-template-columns: 1fr; gap: 2rem; }
  .hero-photo { max-width: 240px; }
  .hero-scan { opacity: 0.35; right: -220px; }
  .project { grid-template-columns: 1fr; gap: 1.4rem; }
  .bg-grid { grid-template-columns: 1fr; gap: 2.5rem; }
}
@media (max-width: 560px) {
  .nav-links { gap: 0.9rem; }
  .nav-links a { font-size: 0.75rem; }
  .section { padding: 3rem 1.2rem; }
}

/* compact project variant (no media column) */
.project-compact { grid-template-columns: 1fr; }
.project-compact .project-body { max-width: 68ch; }