/* Fengyi Zhang — personal site
   Dark researcher / terminal aesthetic */

:root {
  --spot-x: 50%;
  --spot-y: 28%;
  --bg-deep: #0c0e12;
  --bg-elevated: #12151c;
  --bg-card: #161a24;
  --border: rgba(120, 160, 200, 0.12);
  --border-strong: rgba(0, 140, 200, 0.35);
  --text: #e8eaef;
  --text-muted: #8b95a8;
  --accent: #5ab0e0;
  --accent-dim: rgba(90, 176, 224, 0.15);
  --venue-blue: rgb(0, 90, 150);
  --venue-cyan: #4ecdc4;
  --review-amber: #e8b84a;
  --font-serif: "Source Serif 4", "Georgia", serif;
  --font-mono: "JetBrains Mono", "Consolas", "Monaco", monospace;
  --radius: 10px;
  --header-h: 3.5rem;
  --maxw: 52rem;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

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

html {
  scroll-behavior: smooth;
}

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

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-serif);
  font-size: clamp(1rem, 0.95rem + 0.2vw, 1.0625rem);
  line-height: 1.65;
  color: var(--text);
  background: var(--bg-deep);
}

.mono {
  font-family: var(--font-mono);
  font-size: 0.92em;
}

/* Skip link */
.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  padding: 0.5rem 1rem;
  background: var(--accent);
  color: var(--bg-deep);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  z-index: 1000;
  border-radius: 4px;
  text-decoration: none;
}

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

/* Background stack (aurora + grid + scanlines + pointer spotlight) */
.bg-stage {
  pointer-events: none;
  position: fixed;
  inset: 0;
  z-index: -1;
  overflow: hidden;
  background: var(--bg-deep);
}

.bg-aurora {
  position: absolute;
  inset: -20% -10% -10% -10%;
}

.bg-orb {
  position: absolute;
  width: min(48vw, 460px);
  height: min(48vw, 460px);
  border-radius: 50%;
  filter: blur(76px);
  opacity: 0.42;
  mix-blend-mode: screen;
  will-change: transform;
}

.bg-orb--a {
  top: -8%;
  left: 12%;
  background: radial-gradient(circle at 30% 30%, rgba(0, 140, 220, 0.55), transparent 68%);
  animation: orb-drift-a 24s ease-in-out infinite alternate;
}

.bg-orb--b {
  top: 35%;
  right: -5%;
  width: min(42vw, 400px);
  height: min(42vw, 400px);
  background: radial-gradient(circle at 50% 50%, rgba(78, 205, 196, 0.4), transparent 65%);
  animation: orb-drift-b 32s ease-in-out infinite alternate;
}

.bg-orb--c {
  bottom: -12%;
  left: 25%;
  width: min(55vw, 520px);
  height: min(55vw, 520px);
  background: radial-gradient(circle at 40% 60%, rgba(90, 80, 200, 0.35), transparent 70%);
  animation: orb-drift-c 28s ease-in-out infinite alternate;
}

@keyframes orb-drift-a {
  0% {
    transform: translate(0, 0) scale(1);
  }
  100% {
    transform: translate(8%, 12%) scale(1.08);
  }
}

@keyframes orb-drift-b {
  0% {
    transform: translate(0, 0) scale(1);
  }
  100% {
    transform: translate(-10%, 6%) scale(1.05);
  }
}

@keyframes orb-drift-c {
  0% {
    transform: translate(0, 0) scale(1);
  }
  100% {
    transform: translate(-6%, -8%) scale(1.06);
  }
}

.bg-spotlight {
  position: absolute;
  inset: 0;
  background: radial-gradient(
    620px circle at var(--spot-x) var(--spot-y),
    rgba(90, 176, 224, 0.09),
    rgba(78, 205, 196, 0.03) 35%,
    transparent 55%
  );
  transition: background 0.35s var(--ease);
}

@media (prefers-reduced-motion: reduce) {
  .bg-spotlight {
    transition: none;
  }
}

.bg-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(80, 120, 180, 0.055) 1px, transparent 1px),
    linear-gradient(90deg, rgba(80, 120, 180, 0.055) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 85% 72% at 50% 0%, black 22%, transparent 78%);
}

.bg-scanlines {
  position: absolute;
  inset: 0;
  background: repeating-linear-gradient(
    0deg,
    transparent,
    transparent 3px,
    rgba(0, 0, 0, 0.045) 3px,
    rgba(0, 0, 0, 0.045) 4px
  );
  opacity: 0.35;
  mix-blend-mode: overlay;
  pointer-events: none;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(12, 14, 18, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: calc(var(--maxw) + 4rem);
  margin: 0 auto;
  padding: 0 1.25rem;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.logo {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  letter-spacing: -0.02em;
}

.logo-cursor {
  animation: blink 1.1s step-end infinite;
}

@media (prefers-reduced-motion: reduce) {
  .logo-cursor {
    animation: none;
    opacity: 1;
  }
}

@keyframes blink {
  50% {
    opacity: 0;
  }
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 6px;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-card);
  cursor: pointer;
}

.nav-toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  margin: 0 auto;
  background: var(--text);
  border-radius: 1px;
  transition: transform var(--ease) 0.2s, opacity 0.2s;
}

.site-header.nav-open .nav-toggle-bar:first-child {
  transform: translateY(4px) rotate(45deg);
}

.site-header.nav-open .nav-toggle-bar:last-child {
  transform: translateY(-4px) rotate(-45deg);
}

.site-nav .nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 1rem;
}

.site-nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 0.35rem 0;
  border-bottom: 2px solid transparent;
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--accent);
}

.site-nav a.is-active {
  color: var(--text);
  border-bottom-color: var(--venue-cyan);
}

.theme-switch {
  flex-shrink: 0;
  margin-left: 0.75rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  text-decoration: none;
  padding: 0.4rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease), background 0.2s var(--ease);
}

.theme-switch:hover,
.theme-switch:focus-visible {
  color: var(--accent);
  border-color: var(--border-strong);
  background: var(--accent-dim);
}

@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
  }

  .site-nav {
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    background: rgba(12, 14, 18, 0.97);
    border-bottom: 1px solid var(--border);
    padding: 1rem 1.25rem 1.25rem;
    display: none;
  }

  .site-nav.is-open {
    display: block;
  }

  .site-nav .nav-list {
    flex-direction: column;
    gap: 0;
  }

  .site-nav a {
    display: block;
    padding: 0.65rem 0;
    border-bottom-width: 1px;
    border-bottom-color: var(--border);
  }

  .site-nav a.is-active {
    border-bottom-color: var(--venue-cyan);
  }

  .theme-switch {
    margin-left: auto;
    margin-right: 0.5rem;
  }
}

/* Main sections */
main {
  padding-bottom: 4rem;
}

.section {
  padding: 3.5rem 1.25rem;
}

.section-inner {
  max-width: var(--maxw);
  margin: 0 auto;
}

.section-title {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  margin: 0 0 0.5rem;
  font-size: clamp(1.35rem, 1.1rem + 1vw, 1.75rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.section-index {
  color: var(--venue-cyan);
  font-weight: 500;
  font-size: 0.75em;
  opacity: 0.9;
}

.section-label {
  font-family: var(--font-serif);
}

.section-rule {
  height: 2px;
  background: linear-gradient(90deg, var(--border-strong), transparent 85%);
  margin-bottom: 1.75rem;
  border-radius: 1px;
}

.section-lead {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin: -0.5rem 0 1.5rem;
}

/* Hero */
.hero {
  padding: clamp(3rem, 8vw, 5.5rem) 1.25rem 3rem;
  border-bottom: 1px solid var(--border);
}

.hero-inner {
  max-width: calc(var(--maxw) + 6rem);
  margin: 0 auto;
}

.hero-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(140px, 220px);
  gap: clamp(1.5rem, 4vw, 2.75rem);
  align-items: center;
}

.hero-photo-wrap {
  position: relative;
  justify-self: center;
}

.hero-photo {
  display: block;
  width: 100%;
  max-width: 220px;
  aspect-ratio: 1;
  object-fit: cover;
  object-position: center 22%;
  border-radius: 50%;
  border: 2px solid var(--border-strong);
  box-shadow:
    0 0 0 1px var(--accent-dim),
    0 14px 48px rgba(0, 0, 0, 0.4);
}

.hero-main {
  min-width: 0;
}

@media (max-width: 700px) {
  .hero-layout {
    grid-template-columns: 1fr;
    justify-items: center;
    text-align: center;
  }

  .hero-photo-wrap {
    order: -1;
    margin-bottom: 0.25rem;
  }

  .hero-photo {
    max-width: min(200px, 72vw);
  }

  .hero-prompt {
    text-align: left;
    width: 100%;
    max-width: 28rem;
  }

  .hero-links {
    justify-content: center;
  }
}

.hero-prompt {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin: 0 0 1.25rem;
  line-height: 1.5;
}

.prompt-user {
  color: var(--venue-cyan);
}

.prompt-at,
.prompt-path {
  color: var(--text-muted);
}

.prompt-host {
  color: var(--accent);
}

.prompt-cmd {
  color: var(--text);
}

.hero-name {
  margin: 0 0 0.35rem;
  font-size: clamp(2.25rem, 1.5rem + 3vw, 3.25rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.hero-role {
  margin: 0 0 1rem;
  color: var(--text-muted);
  font-size: 1.05rem;
  line-height: 1.5;
}

.hero-role-sub {
  display: inline-block;
  margin-top: 0.15em;
}

.hero-tagline {
  min-height: 1.6em;
  margin: 0 0 1.75rem;
  color: var(--accent);
  font-size: 0.95rem;
}

.hero-tagline::after {
  content: "\258C";
  animation: blink 1s step-end infinite;
  color: var(--venue-cyan);
  margin-left: 2px;
}

@media (prefers-reduced-motion: reduce) {
  .hero-tagline::after {
    animation: none;
  }
}

.hero-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
}

.link-chip {
  display: inline-block;
  padding: 0.45rem 0.85rem;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text);
  text-decoration: none;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.2s var(--ease), background 0.2s var(--ease), color 0.2s;
}

.link-chip:hover,
.link-chip:focus-visible {
  border-color: var(--border-strong);
  background: var(--accent-dim);
  color: var(--accent);
}

/* Research */
.research-body p {
  margin: 0 0 1rem;
}

.research-body p:last-of-type {
  margin-bottom: 1.25rem;
}

.tag-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag-list li {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  padding: 0.35rem 0.65rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text-muted);
}

/* Publications */
.section--pubs {
  background: linear-gradient(180deg, transparent, rgba(0, 60, 100, 0.06) 40%, transparent);
}

.pub-list {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: pub;
}

.pub-card {
  counter-increment: pub;
  margin-bottom: 1rem;
}

.pub-card article {
  position: relative;
  padding: 1.15rem 1.15rem 1.15rem 2.75rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.25s var(--ease), box-shadow 0.25s var(--ease);
}

.pub-card article::before {
  content: "[" counter(pub, decimal-leading-zero) "]";
  position: absolute;
  left: 1rem;
  top: 1.2rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--venue-cyan);
  opacity: 0.85;
}

.pub-card article:hover,
.pub-card article:focus-within {
  border-color: var(--border-strong);
  box-shadow: 0 0 0 1px var(--accent-dim);
}

.pub-title {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.35;
}

.pub-title a {
  color: inherit;
  text-decoration: none;
  border-bottom: 1px solid rgba(90, 176, 224, 0.35);
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.pub-title a:hover,
.pub-title a:focus-visible {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.pub-meta-link {
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
}

.pub-meta-link:hover,
.pub-meta-link:focus-visible {
  text-decoration: underline;
}

.pub-authors {
  margin: 0 0 0.5rem;
  font-size: 0.92rem;
  color: var(--text-muted);
}

.pub-venue {
  margin: 0;
  font-size: 0.85rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem;
}

.badge {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.2rem 0.45rem;
  border-radius: 4px;
}

.badge--conf {
  background: rgba(0, 90, 150, 0.35);
  color: #a8d4f0;
  border: 1px solid rgba(0, 140, 200, 0.4);
}

.badge--review {
  background: rgba(232, 184, 74, 0.15);
  color: var(--review-amber);
  border: 1px solid rgba(232, 184, 74, 0.35);
}

.badge--arxiv {
  background: rgba(130, 150, 190, 0.14);
  color: #b4c5e3;
  border: 1px solid rgba(130, 150, 190, 0.4);
}

.badge--journal {
  background: rgba(78, 205, 196, 0.12);
  color: var(--venue-cyan);
  border: 1px solid rgba(78, 205, 196, 0.35);
}

.badge--oral {
  background: rgba(180, 100, 220, 0.15);
  color: #d4a5f0;
  border: 1px solid rgba(180, 100, 220, 0.35);
}

.venue-name {
  font-weight: 600;
  color: var(--text);
}

.venue-meta {
  color: var(--text-muted);
  font-size: 0.82em;
}

/* Timeline */
.timeline {
  list-style: none;
  margin: 0;
  padding: 0;
}

.timeline-item {
  position: relative;
  display: grid;
  grid-template-columns: 12px 1fr;
  gap: 1rem;
  padding-bottom: 2rem;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-item:not(:last-child)::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 14px;
  bottom: 0;
  width: 2px;
  background: linear-gradient(var(--border-strong), var(--border));
  border-radius: 1px;
}

.timeline-marker {
  width: 12px;
  height: 12px;
  margin-top: 0.35rem;
  background: var(--bg-deep);
  border: 2px solid var(--venue-cyan);
  border-radius: 50%;
  z-index: 1;
}

.timeline-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.35rem 0.75rem;
  margin-bottom: 0.25rem;
}

.timeline-head h3 {
  margin: 0;
  font-size: 1.1rem;
  flex: 1 1 auto;
  min-width: 12ch;
}

.timeline-head time {
  color: var(--text-muted);
  font-size: 0.8rem;
}

.timeline-dash {
  color: var(--text-muted);
}

.timeline-sub {
  margin: 0 0 0.35rem;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.timeline-detail {
  margin: 0 0 0.35rem;
  font-size: 0.92rem;
}

.timeline-detail a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.timeline-detail a:hover,
.timeline-detail a:focus-visible {
  color: var(--venue-cyan);
}

.muted {
  color: var(--text-muted);
  font-size: 0.88rem;
}

/* Awards */
.awards-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.awards-list li {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem 1rem;
  padding: 0.75rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.95rem;
}

.awards-list li:first-child {
  padding-top: 0;
}

.award-title {
  flex: 1 1 12rem;
}

.award-meta {
  color: var(--text-muted);
  font-size: 0.8rem;
  white-space: nowrap;
}

@media (max-width: 520px) {
  .award-meta {
    white-space: normal;
  }
}

/* Service */
.service-list {
  margin: 0;
  padding-left: 1.15rem;
  color: var(--text-muted);
}

.service-list li {
  margin-bottom: 0.5rem;
}

.service-list strong {
  color: var(--text);
}

/* Skills */
.skills-grid {
  margin: 0;
  display: grid;
  gap: 1.25rem;
}

@media (min-width: 600px) {
  .skills-grid {
    grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  }
}

.skill-block {
  padding: 1rem 1.1rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.skill-block dt {
  margin: 0 0 0.4rem;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--venue-cyan);
}

.skill-block dd {
  margin: 0;
  font-size: 0.92rem;
  color: var(--text-muted);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem 1.25rem 2.25rem;
  background: transparent;
}

.footer-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  text-align: center;
}

.footer-copy {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.8125rem;
  letter-spacing: 0.02em;
}