/* ===========================================================================
   Clean / minimalist personal site stylesheet.

   Design system ported from https://github.com/howardhx/website_template
   (tokens, navigation, hero, reveal animations, dark mode, scroll cues).
   The project-page-specific components of the original (video carousels,
   ROI demos, sensor plots, result tabs) are dropped; personal-homepage
   components (avatar, education / publication / project cards) are added
   in the same visual language.
   ========================================================================= */

/* ===== CSS Reset & Custom Properties ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f5f5f7;
  --color-text: #1d1d1f;
  --color-text-secondary: #86868b;
  --color-accent: #0071e3;
  --color-accent-hover: #0077ed;
  --color-highlight-bg: rgba(255, 214, 10, 0.15);
  --color-border: #d2d2d7;
  --color-border-light: #f0f0f0;
  --color-card-bg: #f5f5f7;
  --color-venue: #c5960c;
  --color-red: #d70015;
  --font-primary: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Lato', 'Helvetica Neue', sans-serif;
  /* Height of the fixed nav bar. Content that starts at the top of the page
     has to clear it, since the nav is out of flow. */
  --nav-height: 59px;
  --max-width: 1080px;
  --section-padding: clamp(72px, 9vh, 108px) clamp(20px, 5vw, 40px);
  --transition-reveal: 0.8s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-fast: 0.3s ease;
}

/* ===== Dark Mode ===== */
body.dark-mode {
  --color-bg: #000000;
  --color-bg-alt: #1c1c1e;
  --color-text: #f5f5f7;
  --color-text-secondary: #a1a1a6;
  --color-accent: #2997ff;
  --color-accent-hover: #64b5f6;
  --color-highlight-bg: rgba(255, 214, 10, 0.12);
  --color-border: #38383a;
  --color-border-light: #2c2c2e;
  --color-card-bg: #1c1c1e;
  --color-venue: #e0ab1a;
  --color-red: #ff453a;
}

body.dark-mode .nav-top {
  background: rgba(0, 0, 0, 0.72);
  border-bottom-color: rgba(255, 255, 255, 0.08);
}

body.dark-mode .pub-links a {
  background: var(--color-bg-alt);
  color: var(--color-text);
  border-color: var(--color-border);
}

body.dark-mode .pub-links a:hover {
  background: var(--color-accent);
  color: #000;
  border-color: var(--color-accent);
}

/* ===== Font Faces (Lato) ===== */
@font-face {
  font-family: 'Lato';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: local('Lato Regular'), local('Lato-Regular'), url(https://fonts.gstatic.com/s/lato/v15/S6uyw4BMUTPHjx4wXiWtFCc.woff2) format('woff2');
}
@font-face {
  font-family: 'Lato';
  font-style: normal;
  font-weight: 700;
  font-display: swap;
  src: local('Lato Bold'), local('Lato-Bold'), url(https://fonts.gstatic.com/s/lato/v15/S6u9w4BMUTPHh6UVSwiPGQ3q5d0.woff2) format('woff2');
}

/* ===== Base ===== */
html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-primary);
  font-size: 17px;
  line-height: 1.65;
  color: var(--color-text);
  background: var(--color-bg);
  overflow-x: hidden;
  transition: background 0.3s ease, color 0.3s ease;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

h1, h2, h3 {
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
}

img {
  max-width: 100%;
}

/* Inline emphasis for key terms. Accent-coloured but not underlined, so it
   reads as emphasis rather than a link. Usable anywhere: hero bio, section
   bodies, card text. */
.hl {
  color: var(--color-accent);
  font-weight: 600;
}

a.hl {
  text-decoration: none;
}

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

/* Red variant, for things that should stand apart from the blue accent —
   impact factors, awards, and the like. */
.hl-red {
  color: var(--color-red);
  font-weight: 600;
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--color-text);
  opacity: 0.6;
  padding: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  transition: opacity var(--transition-fast), background var(--transition-fast);
}

.theme-toggle:hover {
  opacity: 1;
  background: rgba(128, 128, 128, 0.1);
}

.icon-sun { display: none; }
.icon-moon { display: block; }
body.dark-mode .icon-sun { display: block; }
body.dark-mode .icon-moon { display: none; }

/* ===== Top Navigation ===== */
.nav-top {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 40px;
  padding: 14px 20px;
}

.nav-link {
  font-size: 14px;
  font-weight: 400;
  color: var(--color-text);
  opacity: 0.7;
  transition: opacity var(--transition-fast);
  text-decoration: none;
}

.nav-home {
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast);
}

.nav-top.scrolled .nav-home {
  opacity: 0.7;
  pointer-events: auto;
}

.nav-link:hover,
.nav-link.active {
  opacity: 1;
  color: var(--color-text);
}

.nav-top:not(.scrolled) .nav-home {
  opacity: 0;
  pointer-events: none;
}

/* ===== Reveal Animations ===== */
.reveal {
  opacity: 0;
  transform: translateY(40px);
  transition: opacity var(--transition-reveal), transform var(--transition-reveal);
}

.reveal.revealed {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Hero Section ===== */
/* The top padding clears the fixed nav. Without it, a hero taller than the
   viewport loses its `margin: auto` centring and the title slides under the
   nav bar. */
.hero {
  min-height: 100vh;
  display: flex;
  padding: calc(var(--nav-height) + 40px) clamp(20px, 5vw, 40px) 48px;
  background: var(--color-bg);
  text-align: center;
  position: relative;
}

.hero-inner {
  max-width: var(--max-width);
  width: 100%;
  margin: auto;
  animation: heroFadeIn 1.2s cubic-bezier(0.16, 1, 0.3, 1) both;
}

@keyframes heroFadeIn {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Two-column hero: text on the left, portrait on the right. Collapses to a
   single centred column below 860px (and whenever there is no photo). */
.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: clamp(32px, 6vw, 80px);
  text-align: left;
}

.hero-grid-single {
  grid-template-columns: minmax(0, 1fr);
  text-align: center;
}

.hero-photo {
  display: flex;
  justify-content: flex-end;
}

.hero-avatar {
  width: clamp(180px, 22vw, 280px);
  height: clamp(180px, 22vw, 280px);
  border-radius: 50%;
  object-fit: cover;
  display: block;
  border: 1px solid var(--color-border);
}

.hero-title {
  font-size: clamp(1.9rem, 4vw, 3rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  padding: 0 0 12px;
  color: var(--color-text);
  position: relative;
  display: block;
}

.hero-role {
  font-size: clamp(15px, 1.55vw, 21px);
  color: var(--color-text);
  line-height: 1.8;
  margin-bottom: 4px;
}

.hero-affiliation {
  font-size: clamp(14px, 1.3vw, 18px);
  color: var(--color-text-secondary);
  margin-bottom: 22px;
}

.hero-affiliation a {
  color: var(--color-text-secondary);
}

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

.hero-bio {
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-text);
  max-width: 720px;
  margin: 0 0 26px;
}

.hero-bio p {
  margin-bottom: 14px;
}

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

.hero-bio ul {
  margin: 0 0 14px;
  padding-left: 20px;
}

.hero-bio li {
  margin-bottom: 6px;
}

.hero-grid-single .hero-bio {
  margin-left: auto;
  margin-right: auto;
}

/* ===== Link Buttons ===== */
.pub-links {
  display: flex;
  gap: 14px;
  justify-content: flex-start;
  flex-wrap: wrap;
}

.hero-grid-single .pub-links {
  justify-content: center;
}

.pub-links a {
  font-size: clamp(12px, 1.2vw, 15px);
  font-weight: 500;
  color: var(--color-accent);
  padding: 7px 16px;
  border-radius: 980px;
  border: 1px solid var(--color-accent);
  transition: all var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.pub-links a:hover {
  background: var(--color-accent);
  color: #fff;
}

.pub-links a svg {
  width: 17px;
  height: 17px;
  flex-shrink: 0;
}

/* ===== Content Sections ===== */
.content-section {
  padding: var(--section-padding);
  background: var(--color-bg);
  position: relative;
}

/* Anchor jumps align the section to y=0, which the fixed nav would cover.
   Applies to the nav links and the in-page scroll arrows alike. */
.hero,
.content-section {
  scroll-margin-top: var(--nav-height);
}

.content-section.alt {
  background: var(--color-bg-alt);
}

.section-inner {
  max-width: var(--max-width);
  width: 100%;
  margin: 0 auto;
}

.section-heading {
  font-size: clamp(1.8rem, 3.4vw, 2.8rem);
  color: var(--color-text);
  margin-bottom: 36px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--color-border);
}

.section-body {
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-text);
}

.section-body p {
  margin-bottom: 16px;
}

.section-body a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 2px;
}

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

.section-body ul {
  margin: 0 0 16px 0;
  padding-left: 22px;
}

.section-body li {
  margin-bottom: 8px;
}

.section-body strong {
  font-weight: 700;
}

.subsection-heading {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: 0;
  color: var(--color-text);
  margin: 40px 0 18px;
}

/* ===== Education / Experience list ===== */
.edu-list {
  display: flex;
  flex-direction: column;
  gap: 22px;
}

.edu-item {
  display: flex;
  align-items: flex-start;
  gap: 18px;
}

.edu-logo {
  width: 52px;
  height: 52px;
  object-fit: contain;
  flex-shrink: 0;
  border-radius: 8px;
}

.edu-text {
  flex-grow: 1;
  min-width: 0;
}

.edu-school {
  font-size: 17px;
  font-weight: 600;
  color: var(--color-text);
}

.edu-meta {
  font-size: 14px;
  color: var(--color-text-secondary);
  display: block;
}

.edu-date {
  font-size: 14px;
  color: var(--color-text-secondary);
  white-space: nowrap;
  flex-shrink: 0;
  padding-top: 2px;
}

/* ===== Publication / Project cards ===== */
.card-list {
  display: flex;
  flex-direction: column;
  gap: 34px;
}

.card-item {
  display: flex;
  align-items: flex-start;
  gap: 26px;
}

/* `contain` rather than `cover`: these thumbnails are paper figures, so
   cropping them loses the panels that make them readable. Wide or tall
   figures letterbox against the card background instead. */
.card-thumb {
  width: 240px;
  flex-shrink: 0;
  aspect-ratio: 4 / 3;
  object-fit: contain;
  border-radius: 10px;
  border: 1px solid var(--color-border-light);
  background: #fff;
  padding: 6px;
  display: block;
}

body.dark-mode .card-thumb {
  background: var(--color-bg-alt);
  border-color: var(--color-border);
}

.card-body {
  flex-grow: 1;
  min-width: 0;
}

.card-title {
  font-size: 17px;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: -0.01em;
  color: var(--color-text);
  margin-bottom: 6px;
}

.card-authors {
  font-size: 15px;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 2px;
}

.card-authors .me {
  color: var(--color-text);
  font-weight: 700;
}

.card-venue {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-venue);
  line-height: 1.6;
  margin-bottom: 10px;
}

.card-org {
  font-size: 15px;
  color: var(--color-text-secondary);
  margin-bottom: 10px;
}

.card-desc {
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-text);
  margin-bottom: 6px;
}

.card-role {
  font-size: 13px;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 10px;
}

.card-links {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.card-links a {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-accent);
  padding: 3px 13px;
  border-radius: 980px;
  border: 1px solid var(--color-accent);
  transition: all var(--transition-fast);
}

.card-links a:hover {
  background: var(--color-accent);
  color: #fff;
}

/* ===== Scroll Down Arrow ===== */
.scroll-arrow {
  display: block;
  position: absolute;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%);
  color: var(--color-text-secondary);
  opacity: 0.5;
  text-decoration: none;
  cursor: pointer;
  animation: bounceArrow 2s ease-in-out infinite;
  z-index: 10;
  padding: 10px;
}

.hero-scroll-arrow {
  position: static;
  transform: none;
  margin-top: 8px;
  display: inline-block;
  animation: bounceArrowInline 2s ease-in-out infinite;
}

@keyframes bounceArrowInline {
  0%, 100% { transform: translateY(0); opacity: 0.5; }
  50% { transform: translateY(10px); opacity: 1; }
}

.scroll-arrow:hover {
  opacity: 1;
  color: var(--color-accent);
}

.hero-scroll-row {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  margin-top: 26px;
}

.hero-scroll-cta {
  display: flex;
  align-items: center;
  gap: 10px;
}

.scroll-hint {
  font-size: 12px;
  color: var(--color-text-secondary);
  opacity: 0.6;
  letter-spacing: 0.05em;
}

@keyframes bounceArrow {
  0%, 100% { transform: translateX(-50%) translateY(0); opacity: 0.5; }
  50% { transform: translateX(-50%) translateY(10px); opacity: 1; }
}

/* ===== Footer ===== */
.site-footer {
  text-align: center;
  padding: 40px 20px;
  font-size: 13px;
  color: var(--color-text-secondary);
  border-top: 1px solid var(--color-border);
}

.site-footer a {
  color: var(--color-accent);
  text-decoration: underline;
  text-underline-offset: 2px;
}

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

/* ===== Section background overrides ===== */
body:not(.dark-mode) .hero {
  background: #fdfdfd;
}

body.dark-mode .hero,
body.dark-mode .content-section,
body.dark-mode .content-section.alt {
  background: #090d12;
}

/* ===== Responsive ===== */

/* The hero needs to stack earlier than the rest of the page — two columns get
   cramped well before the 768px breakpoint. The photo moves above the text. */
@media (max-width: 860px) {
  .hero-grid {
    grid-template-columns: minmax(0, 1fr);
    justify-items: center;
    text-align: center;
    gap: 28px;
  }

  .hero-photo {
    order: -1;
    justify-content: center;
  }

  .hero-avatar {
    width: clamp(140px, 34vw, 200px);
    height: clamp(140px, 34vw, 200px);
  }

  .hero-bio {
    margin-left: auto;
    margin-right: auto;
  }

  /* Name and buttons centre when stacked, but the bio is prose with a bullet
     list — centring it leaves the list ragged and hard to read. The 404 hero
     (hero-grid-single) is one short sentence, so it stays centred. */
  .hero-grid:not(.hero-grid-single) .hero-bio {
    text-align: left;
  }

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

@media (max-width: 768px) {
  /* Narrower nav padding below this breakpoint makes the bar shorter. */
  :root {
    --nav-height: 51px;
  }

  .nav-inner {
    gap: 16px;
    padding: 10px 16px;
    justify-content: flex-start;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }

  .nav-inner::-webkit-scrollbar {
    display: none;
  }

  .nav-link {
    font-size: 12px;
    white-space: nowrap;
    flex-shrink: 0;
  }

  .hero {
    padding: calc(var(--nav-height) + 28px) 16px 56px;
  }

  .hero-title {
    line-height: 1.2;
    padding: 20px 0 10px;
  }

  .content-section {
    padding: 60px 16px;
  }

  .section-heading {
    font-size: 1.6rem;
    margin-bottom: 26px;
  }

  .card-item {
    flex-direction: column;
    gap: 14px;
  }

  .card-thumb {
    width: 100%;
  }

  /* Flex wrapping put the date in a different place depending on how long the
     school line was. A grid keeps the logo, text and date in the same spot for
     every entry. */
  .edu-item {
    display: grid;
    grid-template-columns: 52px 1fr;
    grid-template-areas:
      "logo text"
      ".    date";
    gap: 4px 14px;
    align-items: start;
  }

  .edu-logo { grid-area: logo; }
  .edu-text { grid-area: text; }

  .edu-date {
    grid-area: date;
    white-space: normal;
  }

  .scroll-arrow {
    bottom: 16px;
  }
}

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

  .reveal,
  .reveal.revealed {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .hero-inner,
  .scroll-arrow,
  .hero-scroll-arrow {
    animation: none;
  }
}