/* ------------------------------------------------------------------
   Hao Yu — academic portfolio
   Palette: ink on warm paper; single restrained accent for links
   Replace fonts in :root if you self-host or change stack
   ------------------------------------------------------------------ */

:root {
  --ink: #141820;
  --ink-muted: #4b5563;
  --ink-faint: #8b939e;
  --paper: #fafaf8;
  --paper-elevated: #ffffff;
  --line: #e6e4df;
  --line-strong: #d1cec7;
  --accent: #1e3a5f;
  --accent-hover: #152a45;
  --radius: 6px;
  --shadow: 0 1px 2px rgba(20, 24, 32, 0.06);
  --shadow-hover: 0 8px 24px rgba(20, 24, 32, 0.08);
  --max: 1120px;
  --font-sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-serif: "Source Serif 4", "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --space-section: clamp(3.5rem, 6vw, 5.5rem);
}

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.65;
  font-feature-settings: "kern" 1, "liga" 1;
}

body.nav-open {
  overflow: hidden;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
  transition: color 0.15s ease, text-decoration-color 0.15s ease;
}

a:hover {
  color: var(--accent-hover);
}

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

.skip-link {
  position: absolute;
  left: -999px;
  top: 0.75rem;
  padding: 0.5rem 1rem;
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  z-index: 100;
  border-radius: var(--radius);
}

.skip-link:focus {
  left: 0.75rem;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.site-header.is-scrolled {
  border-bottom-color: var(--line);
  box-shadow: var(--shadow);
}

.header-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 1.05rem;
  letter-spacing: -0.02em;
}

.brand a {
  color: var(--ink);
  text-decoration: none;
}

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

.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper-elevated);
  cursor: pointer;
}

.nav-toggle-bar {
  display: block;
  width: 1.1rem;
  height: 2px;
  background: var(--ink);
  position: relative;
}

.nav-toggle-bar::before,
.nav-toggle-bar::after {
  content: "";
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--ink);
  transition: transform 0.2s ease;
}

.nav-toggle-bar::before {
  top: -6px;
}

.nav-toggle-bar::after {
  top: 6px;
}

.site-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.15rem 0.5rem;
  justify-content: flex-end;
}

.site-nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--ink-muted);
  text-decoration: none;
  padding: 0.35rem 0.55rem;
  border-radius: 4px;
  transition: color 0.15s ease, background 0.15s ease;
}

.site-nav a:hover {
  color: var(--ink);
  background: color-mix(in srgb, var(--line) 45%, transparent);
}

@media (max-width: 880px) {
  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    position: fixed;
    inset: 0 0 auto 0;
    top: 3.6rem;
    flex-direction: column;
    align-items: stretch;
    padding: 1rem 1.5rem 1.25rem;
    background: var(--paper);
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-hover);
    max-height: min(70vh, 480px);
    overflow-y: auto;
    transform-origin: top;
    transform: scaleY(0.96);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease, transform 0.2s ease;
  }

  .site-nav.is-open {
    opacity: 1;
    transform: scaleY(1);
    pointer-events: auto;
  }

  .site-nav a {
    padding: 0.65rem 0.5rem;
    border-radius: var(--radius);
  }
}

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 1.5rem 4rem;
}

.section {
  padding: var(--space-section) 0;
  border-bottom: 1px solid var(--line);
}

.section:last-of-type {
  border-bottom: none;
}

.section-label {
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 0.75rem;
}

.section h2 {
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: clamp(1.45rem, 2.5vw, 1.75rem);
  letter-spacing: -0.02em;
  margin: 0 0 1.25rem;
  line-height: 1.25;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 220px;
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
  padding-top: clamp(2.5rem, 5vw, 3.75rem);
  padding-bottom: var(--space-section);
  border-bottom: 1px solid var(--line);
}

@media (max-width: 768px) {
  .hero {
    grid-template-columns: 1fr;
  }
}

.hero-copy h1 {
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: clamp(2rem, 4.5vw, 2.75rem);
  letter-spacing: -0.03em;
  line-height: 1.12;
  margin: 0 0 0.5rem;
}

.hero-title-line {
  font-size: clamp(1rem, 2vw, 1.125rem);
  font-weight: 500;
  color: var(--ink-muted);
  margin: 0 0 0.35rem;
}

.hero-location {
  font-size: 0.95rem;
  color: var(--ink-faint);
  margin: 0 0 1.5rem;
}

.hero-summary {
  font-size: 1.05rem;
  max-width: 52ch;
  color: var(--ink-muted);
  margin: 0 0 1.75rem;
}

.hero-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  align-items: center;
  margin: 0;
  padding: 0;
  list-style: none;
}

.hero-links li {
  display: flex;
  align-items: center;
}

.hero-links a {
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  border-bottom: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
  padding-bottom: 0.1rem;
}

.hero-links a:hover {
  border-bottom-color: var(--accent);
}

.hero-links .sep {
  color: var(--line-strong);
  user-select: none;
}

.headshot {
  margin: 0;
  justify-self: end;
  width: 100%;
  max-width: 220px;
}

@media (max-width: 768px) {
  .headshot {
    justify-self: start;
    max-width: 160px;
  }
}

.headshot-placeholder {
  aspect-ratio: 4 / 5;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--paper-elevated);
  box-shadow: var(--shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--ink-faint);
  font-size: 0.8rem;
  text-align: center;
  padding: 1rem;
  line-height: 1.4;
}

.headshot-placeholder strong {
  display: block;
  font-family: var(--font-serif);
  font-size: 1.75rem;
  color: var(--ink-muted);
  letter-spacing: 0.04em;
}

.prose p {
  margin: 0 0 1rem;
  max-width: 68ch;
  color: var(--ink-muted);
}

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

.judge-summary {
  font-size: 0.95rem;
  color: var(--ink-muted);
  margin: 0 0 0.65rem;
  max-width: 62ch;
}

.theme-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
}

.theme-card {
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.25rem 1.4rem;
  box-shadow: var(--shadow);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.theme-card:hover {
  border-color: var(--line-strong);
  box-shadow: var(--shadow-hover);
}

.theme-card h3 {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  font-weight: 600;
  margin: 0 0 0.65rem;
  letter-spacing: -0.01em;
}

.theme-card p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--ink-muted);
}

.pub-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.pub-card {
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem 1.35rem;
  box-shadow: var(--shadow);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.pub-card:hover {
  border-color: var(--line-strong);
  box-shadow: var(--shadow-hover);
}

.pub-card--featured {
  border-color: color-mix(in srgb, var(--accent) 22%, var(--line));
}

.pub-card h3 {
  font-family: var(--font-serif);
  font-size: 1.08rem;
  font-weight: 600;
  margin: 0 0 0.5rem;
  line-height: 1.35;
  letter-spacing: -0.01em;
}

.pub-meta {
  font-size: 0.88rem;
  color: var(--ink-muted);
  margin: 0 0 0.35rem;
}

.pub-venue {
  font-size: 0.88rem;
  color: var(--ink-faint);
  margin: 0 0 0.65rem;
}

.pub-note {
  font-size: 0.92rem;
  color: var(--ink-muted);
  margin: 0;
  padding-top: 0.5rem;
  border-top: 1px dashed var(--line);
}

.pub-links {
  margin: 0.65rem 0 0;
  font-size: 0.85rem;
}

.project-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.25rem;
}

.project-card {
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.35rem 1.25rem;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  min-height: 100%;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.project-card:hover {
  border-color: var(--line-strong);
  box-shadow: var(--shadow-hover);
}

.project-card h3 {
  font-family: var(--font-serif);
  font-size: 1.08rem;
  font-weight: 600;
  margin: 0 0 0.35rem;
  letter-spacing: -0.01em;
}

.project-meta {
  font-size: 0.82rem;
  color: var(--ink-faint);
  margin: 0 0 0.75rem;
}

.project-tools {
  font-size: 0.82rem;
  color: var(--ink-muted);
  margin: 0 0 0.85rem;
}

.project-tools strong {
  font-weight: 600;
  color: var(--ink);
}

.project-card ul {
  margin: 0 0 1rem;
  padding-left: 1.1rem;
  color: var(--ink-muted);
  font-size: 0.93rem;
}

.project-card li {
  margin-bottom: 0.35rem;
}

.project-focus {
  margin-top: auto;
  font-size: 0.88rem;
  color: var(--ink);
  border-top: 1px solid var(--line);
  padding-top: 0.85rem;
}

.project-focus strong {
  font-weight: 600;
}

.timeline {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.timeline-item {
  display: grid;
  grid-template-columns: 140px minmax(0, 1fr);
  gap: 1rem 1.5rem;
  align-items: baseline;
}

@media (max-width: 600px) {
  .timeline-item {
    grid-template-columns: 1fr;
    gap: 0.35rem;
  }
}

.timeline-date {
  font-size: 0.85rem;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}

.timeline-body h3 {
  font-family: var(--font-serif);
  font-size: 1.05rem;
  font-weight: 600;
  margin: 0 0 0.25rem;
}

.timeline-body .org {
  font-size: 0.92rem;
  color: var(--ink-muted);
  margin: 0 0 0.5rem;
}

.timeline-body ul {
  margin: 0;
  padding-left: 1.1rem;
  color: var(--ink-muted);
  font-size: 0.93rem;
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
}

.skill-block {
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem 1.25rem;
  box-shadow: var(--shadow);
}

.skill-block h3 {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 0.65rem;
}

.skill-block p {
  margin: 0;
  font-size: 0.93rem;
  color: var(--ink-muted);
}

.list-plain {
  list-style: none;
  margin: 0;
  padding: 0;
}

.list-plain li {
  padding: 0.65rem 0;
  border-bottom: 1px solid var(--line);
  color: var(--ink-muted);
  font-size: 0.95rem;
}

.list-plain li:last-child {
  border-bottom: none;
}

.list-plain strong {
  color: var(--ink);
  font-weight: 600;
}

.cv-panel {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  background: var(--paper-elevated);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.5rem;
  box-shadow: var(--shadow);
}

.cv-panel p {
  margin: 0;
  max-width: 48ch;
  color: var(--ink-muted);
  font-size: 0.95rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.65rem 1.15rem;
  border-radius: var(--radius);
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #f8fafc;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.15s ease;
}

.btn:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: #fff;
}

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

.btn:active {
  transform: translateY(1px);
}

.contact-block {
  max-width: 52ch;
}

.contact-block p {
  color: var(--ink-muted);
  margin: 0 0 0.75rem;
}

.contact-dl {
  margin: 1rem 0 0;
  display: grid;
  gap: 0.5rem;
}

.contact-dl div {
  display: grid;
  grid-template-columns: 92px 1fr;
  gap: 0.5rem;
  font-size: 0.95rem;
}

.contact-dl dt {
  color: var(--ink-faint);
  font-weight: 500;
}

.contact-dl dd {
  margin: 0;
  color: var(--ink-muted);
}

.site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 2rem 1.5rem 3rem;
  color: var(--ink-faint);
  font-size: 0.82rem;
  border-top: 1px solid var(--line);
}

.site-footer__line {
  margin: 0 0 0.5rem;
}

.site-footer__meta {
  margin: 0;
  max-width: 52ch;
  line-height: 1.5;
}

.site-footer__meta a {
  font-weight: 500;
}

.site-footer__sep {
  margin: 0 0.35rem;
  color: var(--line-strong);
}

.site-footer__hint {
  color: var(--ink-faint);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}