/* ==========================================================================
   junzengx14.github.io — site styles

   Layered on top of Bootstrap 5 (grid + a few utilities only). No jQuery.
   NOTE: css/main.css is a separate stylesheet for the Jekyll blog layout
   (_layouts/*.html, blog.html). Don't merge the two.
   ========================================================================== */

:root {
  --ink: #222;
  --body: #484848;
  --muted: #777;
  --gray-bg: #f2f2f2;
  --line: #e6e6e6;
  --accent: #2a7ae2;
  --nav-h: 70px;
}

/* --------------------------------------------------------------- base --- */

html {
  scroll-behavior: smooth;
  /* keep anchored sections clear of the fixed navbar */
  scroll-padding-top: var(--nav-h);
}

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

body {
  font-family: "Raleway", -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  color: var(--body);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 { color: var(--ink); }

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--ink); text-decoration: underline; }

/* ----------------------------------------------------------- sections --- */

.section { padding: 100px 0; }
.bg-gray { background-color: var(--gray-bg); }

.heading { margin-bottom: 50px; }

.heading h2 {
  font-size: 32px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.02em;
  margin: 0;
}

.heading h6 {
  font-size: 16px;
  font-weight: 500;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 10px;
}

.main-btn {
  display: inline-block;
  background-color: var(--ink);
  border: 2px solid var(--ink);
  color: #fff;
  padding: 10px 20px;
  text-transform: uppercase;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.05em;
  transition: background-color 0.25s, color 0.25s;
}

.main-btn:hover {
  background-color: transparent;
  color: var(--ink);
  text-decoration: none;
}

/* ------------------------------------------------------------- navbar --- */

.site-nav {
  transition: background-color 0.3s, box-shadow 0.3s, padding 0.3s;
  background-color: transparent;
  padding-top: 14px;
  padding-bottom: 14px;
}

.site-nav.is-scrolled,
.site-nav.is-solid {
  background-color: var(--ink);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.25);
  padding-top: 8px;
  padding-bottom: 8px;
}

.site-nav .navbar-brand {
  color: #fff;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.site-nav .nav-link {
  color: rgba(255, 255, 255, 0.8);
  text-transform: uppercase;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.06em;
  padding: 8px 14px;
}

.site-nav .nav-link:hover,
.site-nav .nav-link.active {
  color: #fff;
  text-decoration: none;
}

/* the collapsed mobile menu needs its own backdrop over a transparent navbar */
@media (max-width: 991.98px) {
  .site-nav .navbar-collapse.show,
  .site-nav .navbar-collapse.collapsing {
    background-color: var(--ink);
    margin: 10px -12px -14px;
    padding: 10px 12px;
  }
}

/* --------------------------------------------------------------- hero --- */

.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  overflow: hidden;
  color: #fff;
  /* Plain grey by design — the banner deliberately carries no photograph.
     Dark enough that the white heading clears WCAG AA at these type sizes. */
  background: linear-gradient(135deg, #3f4449 0%, #5c6268 100%);
}

.hero .container { position: relative; z-index: 2; }

.hero h1 {
  color: #fff;
  font-weight: 900;
  font-size: clamp(38px, 8vw, 88px);
  line-height: 1.1;
  margin: 0;
}

.hero .hero-sub {
  font-size: clamp(18px, 2.6vw, 24px);
  color: #eee;
  margin-top: 30px;
}

.hero .hero-scroll {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 2;
  color: #fff;
  font-size: 26px;
  opacity: 0.8;
  animation: hero-bob 2s ease-in-out infinite;
}

.hero .hero-scroll:hover { opacity: 1; text-decoration: none; }

@keyframes hero-bob {
  0%, 100% { transform: translate(-50%, 0); }
  50%      { transform: translate(-50%, 10px); }
}

/* Rotating tagline — replaces Boyuan's animated.headline.js with pure CSS.
   Three phrases, 9s cycle, each visible for a third of it. */
.rotator {
  display: inline-grid;
  vertical-align: bottom;
}

.rotator b {
  grid-area: 1 / 1;
  font-weight: 700;
  opacity: 0;
  white-space: nowrap;
  animation: rotate-phrase 9s linear infinite;
}

.rotator b:nth-child(2) { animation-delay: 3s; }
.rotator b:nth-child(3) { animation-delay: 6s; }

@keyframes rotate-phrase {
  0%    { opacity: 0; transform: translateY(8px); }
  4%    { opacity: 1; transform: translateY(0); }
  30%   { opacity: 1; transform: translateY(0); }
  34%   { opacity: 0; transform: translateY(-8px); }
  100%  { opacity: 0; transform: translateY(-8px); }
}

@media (prefers-reduced-motion: reduce) {
  .hero .hero-scroll { animation: none; }
  .rotator b { animation: none; opacity: 0; }
  .rotator b:first-child { opacity: 1; }
}

/* -------------------------------------------------------------- about --- */

.portrait {
  width: 100%;
  aspect-ratio: 4 / 5;
  border-radius: 4px;
  overflow: hidden;
  /* placeholder shown until assets/profile/portrait.jpg exists */
  background: repeating-linear-gradient(45deg, #e9e9e9, #e9e9e9 12px, #e2e2e2 12px, #e2e2e2 24px);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #aaa;
}

.portrait .portrait-placeholder { font-size: 44px; }
.portrait img { width: 100%; height: 100%; object-fit: cover; display: none; }
.portrait.has-photo img { display: block; }
.portrait.has-photo .portrait-placeholder { display: none; }

.about-subtitle {
  font-size: 20px;
  font-weight: 600;
  color: var(--muted);
  margin-bottom: 24px;
}

.about-actions {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 24px;
  margin-top: 30px;
}

.social-links a {
  font-size: 34px;
  margin-right: 20px;
  color: #555;
}

.social-links a:last-child { margin-right: 0; }
.social-links a:hover { color: var(--accent); text-decoration: none; }
/* the Google Scholar glyph renders larger than the rest — shrink it to match */
.social-links .ai { font-size: 29px; }

/* ------------------------------------------- experience / education --- */

.cv-card {
  display: flex;
  gap: 20px;
  padding: 20px 0;
  border-bottom: 1px solid var(--line);
}

.cv-card:last-child { border-bottom: 0; }

/* Wider than tall: the university logos are square, but the company logos are
   wordmarks (Cruise ~3.4:1, Cyan ~2.1:1) that would shrink to a thin strip in a
   square box. 110x90 gives them usable width and still centres square marks. */
.cv-logo {
  flex: 0 0 110px;
  width: 110px;
  height: 90px;
  padding: 8px;
  border-radius: 4px;
  background-color: #fff;
  border: 1px solid var(--line);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.cv-logo img { max-width: 100%; max-height: 100%; object-fit: contain; display: none; }
.cv-logo.has-logo img { display: block; }
.cv-logo.has-logo .cv-lettermark { display: none; }

/* fallback while assets/experience/*.png don't exist */
.cv-lettermark {
  font-size: 34px;
  font-weight: 800;
  color: #9aa5b1;
  letter-spacing: -0.02em;
}

.cv-body { flex: 1 1 auto; min-width: 0; }
.cv-org { font-weight: 700; color: var(--ink); }

/* org names link out, but should read as headings rather than body links */
.cv-org a { color: inherit; }
.cv-org a:hover { color: var(--accent); text-decoration: none; }

.cv-dates { color: var(--muted); white-space: nowrap; }
.cv-role { font-weight: 600; }
.cv-detail { color: var(--body); margin: 0; }

.cv-head {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

/* ------------------------------------------------------- publications --- */

.pub-row { margin-bottom: 45px; }
.pub-row:last-child { margin-bottom: 0; }

/* Cover images range from 0.75:1 to 4.3:1, so `contain` on a fixed 16:9 box —
   `cover` would crop the wide ones into unreadable strips. */
.paper-thumbnail {
  position: relative;
  aspect-ratio: 16 / 9;
  background-color: #fff;
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
}

/* The box takes its height from `aspect-ratio`, not an explicit value. A child
   using `height: 100%` against that can resolve to `auto`, collapsing the link
   to zero height and taking the image with it — the thumbnail then renders
   blank. Absolute positioning gives the link a definite box to fill, so the
   image always has a real height to be `contain`-fitted into. */
.paper-thumbnail a,
.paper-thumbnail span {
  position: absolute;
  inset: 0;
  display: block;
}

.paper-thumbnail img { width: 100%; height: 100%; object-fit: contain; }

.pub-title {
  font-size: 19px;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.35;
  display: inline-block;
}

.pub-title:hover { color: var(--accent); text-decoration: none; }

.pub-authors { margin: 8px 0 0; }
.pub-venue { margin: 2px 0 0; }
.pub-note { margin: 4px 0 0; }
.pub-award { color: #c0392b; }
.pub-links { margin: 12px 0 0; font-size: 15px; }

.pub-panel {
  margin-top: 12px;
  padding: 14px 16px;
  background-color: #fff;
  border: 1px solid var(--line);
  border-radius: 4px;
  font-size: 15px;
}

.pub-panel pre { margin: 0; white-space: pre-wrap; font-size: 13px; }

@media (max-width: 767.98px) {
  .paper-thumbnail { margin-bottom: 16px; }
}

/* ----------------------------------------------------------- projects --- */

.filter-bar {
  list-style: none;
  padding: 0;
  margin: -30px 0 40px;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 10px;
}

.filter-bar li {
  cursor: pointer;
  padding: 6px 16px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
  user-select: none;
  transition: background-color 0.2s, color 0.2s, border-color 0.2s;
}

.filter-bar li:hover { color: var(--ink); border-color: #ccc; }

.filter-bar li.is-active {
  background-color: var(--ink);
  border-color: var(--ink);
  color: #fff;
}

.project-item { margin-bottom: 30px; }
.project-item[hidden] { display: none; }

.item-content {
  position: relative;
  aspect-ratio: 4 / 3;
  border-radius: 4px;
  overflow: hidden;
  /* placeholder tiles are a gradient, so an absent image never shows as broken */
  background: linear-gradient(135deg, #cfd8dc 0%, #90a4ae 100%);
}

.item-content img { width: 100%; height: 100%; object-fit: cover; }

.item-overlay {
  position: absolute;
  inset: 0;
  padding: 22px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  color: #fff;
  background: linear-gradient(to top, rgba(0, 0, 0, 0.78) 0%, rgba(0, 0, 0, 0.15) 55%, transparent 100%);
  opacity: 0;
  transition: opacity 0.3s;
}

.item-content:hover .item-overlay,
.item-content:focus-within .item-overlay { opacity: 1; }

.item-overlay h6 {
  color: #fff;
  font-weight: 700;
  font-size: 17px;
  margin: 0 0 6px;
}

.item-overlay p { margin: 0; font-size: 14px; color: #e4e4e4; }

/* touch devices have no hover — show the caption permanently */
@media (hover: none) {
  .item-overlay { opacity: 1; }
}

/* ------------------------------------------------- awards and service --- */

.plain-list { padding-left: 20px; margin: 0; }
.plain-list li { margin-bottom: 6px; }

.subheading {
  font-size: 15px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink);
  margin: 30px 0 12px;
}

.subheading:first-child { margin-top: 0; }

.service-summary { margin-bottom: 0; }

/* ---------------------------------------------------------- blog --- */

.blog-empty {
  text-align: center;
  padding: 40px 0;
}

.blog-empty p { color: var(--muted); margin-bottom: 24px; }

.blog-item {
  background-color: #fff;
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
  height: 100%;
}

.blog-item .blog-img { aspect-ratio: 16 / 9; background-color: #e9e9e9; }
.blog-item .blog-img img { width: 100%; height: 100%; object-fit: cover; }
.blog-item .blog-content { padding: 22px; }
.blog-item .blog-content h3 { font-size: 19px; font-weight: 700; margin-bottom: 10px; }
.blog-item .blog-meta { color: var(--muted); font-size: 14px; }

/* ------------------------------------------------------------- pages --- */

/* publications.html / service.html have no hero, so push content past the navbar */
.page-body { padding-top: calc(var(--nav-h) + 60px); }

.back-link {
  display: inline-block;
  margin-bottom: 20px;
  font-size: 14px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ------------------------------------------------------------ footer --- */

.site-footer {
  background-color: var(--ink);
  color: #bbb;
  padding: 30px 0;
  font-size: 14px;
}

.site-footer a { color: #ddd; }

/* the clustrmaps widget renders a wide canvas — keep it from forcing h-scroll */
.site-footer #clustrmaps-container { max-width: 100%; overflow: hidden; }

/* ------------------------------------------------------- small screens --- */

@media (max-width: 767.98px) {
  .section { padding: 60px 0; }
  .heading { margin-bottom: 30px; }
  .heading h2 { font-size: 26px; }
  .cv-card { flex-direction: row; gap: 14px; }
  .cv-logo { flex-basis: 74px; width: 74px; height: 60px; padding: 5px; }
  .cv-lettermark { font-size: 24px; }
  .cv-dates { white-space: normal; }
  .social-links a { font-size: 28px; margin-right: 16px; }
  .social-links .ai { font-size: 24px; }
  .page-body { padding-top: calc(var(--nav-h) + 30px); }
}