/* ============================================================
   Minzhou Li · Personal Homepage
   Theme: willow green, light / dark, bilingual (EN / ZH)
   ============================================================ */

/* ---------- Design tokens ---------- */
:root {
  --bg: #f7f6f3;
  --bg-soft: #f1efea;
  --surface: #ffffff;
  --text: #21251f;
  --text-2: #4d544e;
  --muted: #7a827c;
  --line: #e6e2da;
  --line-soft: #edeae2;
  --accent: #3d7a62;
  --accent-2: #6fa58c;
  --accent-soft: rgba(61, 122, 98, 0.09);
  --accent-text: #2f5f4b;
  --on-accent: #ffffff;
  --shadow: 0 1px 2px rgba(33, 37, 31, 0.04), 0 10px 28px -14px rgba(33, 37, 31, 0.14);
  --shadow-lg: 0 2px 6px rgba(33, 37, 31, 0.05), 0 26px 52px -22px rgba(33, 37, 31, 0.2);
  --radius: 16px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", "Helvetica Neue",
    Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "JetBrains Mono",
    Menlo, Consolas, monospace;
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #0e1211;
  --bg-soft: #121716;
  --surface: #161c1a;
  --text: #e7eae7;
  --text-2: #b8c0ba;
  --muted: #8d968f;
  --line: #252c29;
  --line-soft: #1e2422;
  --accent: #6fb99a;
  --accent-2: #4d8a70;
  --accent-soft: rgba(111, 185, 154, 0.12);
  --accent-text: #8fcfb2;
  --on-accent: #0c211a;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 12px 30px -16px rgba(0, 0, 0, 0.55);
  --shadow-lg: 0 2px 6px rgba(0, 0, 0, 0.35), 0 28px 56px -24px rgba(0, 0, 0, 0.65);
  color-scheme: dark;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 84px;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color 0.35s ease, color 0.35s ease;
}

a { color: inherit; text-decoration: none; }

img, svg { display: block; }

::selection { background: var(--accent); color: var(--on-accent); }

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 4px;
}

.container {
  width: min(1000px, 92vw);
  margin-inline: auto;
}

.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 100;
  padding: 8px 16px;
  border-radius: 8px;
  background: var(--accent);
  color: var(--on-accent);
  font-size: 14px;
  transform: translateY(-200%);
  transition: transform 0.2s;
}
.skip-link:focus { transform: none; }

/* ---------- Bilingual visibility ---------- */
[data-lang="en"] [data-lang="zh"],
[data-lang="zh"] [data-lang="en"] { display: none; }

/* ---------- Scroll progress ---------- */
.progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 70;
  width: 100%;
  height: 3px;
  background: linear-gradient(90deg, var(--accent-2), var(--accent));
  transform: scaleX(0);
  transform-origin: 0 50%;
}

/* ---------- Top navigation ---------- */
.nav {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 50;
  border-bottom: 1px solid transparent;
  transition: background-color 0.3s ease, border-color 0.3s ease;
}
.nav.scrolled {
  background: var(--bg);
  background: color-mix(in oklab, var(--bg) 84%, transparent);
  -webkit-backdrop-filter: blur(14px) saturate(1.5);
  backdrop-filter: blur(14px) saturate(1.5);
  border-bottom-color: var(--line-soft);
}

.nav-inner {
  width: min(1000px, 92vw);
  margin-inline: auto;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 9px;
  font-weight: 700;
  font-size: 15.5px;
  letter-spacing: 0.01em;
}
.brand::before {
  content: "";
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--accent);
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}
.brand:hover::before { transform: scale(1.35); }

.nav-links { display: flex; gap: 4px; }
.nav-links a {
  padding: 7px 13px;
  border-radius: 999px;
  font-size: 14.5px;
  color: var(--text-2);
  transition: color 0.2s ease, background-color 0.2s ease;
}
.nav-links a:hover { color: var(--text); background: var(--accent-soft); }
.nav-links a.active { color: var(--accent-text); background: var(--accent-soft); }

.nav-actions {
  display: flex;
  align-items: center;
  gap: 10px;
}

/* Language switch pill */
.lang-switch {
  position: relative;
  display: flex;
  align-items: stretch;
  padding: 3px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  transition: border-color 0.2s;
}
.lang-switch:hover { border-color: var(--accent-2); }

.lang-opt {
  position: relative;
  z-index: 1;
  padding: 3px 12px;
  border: 0;
  background: none;
  border-radius: 999px;
  font-family: var(--font-sans);
  font-size: 12.5px;
  font-weight: 600;
  line-height: 1.6;
  color: var(--muted);
  cursor: pointer;
  transition: color 0.25s ease;
}
.lang-opt:hover { color: var(--text-2); }
.lang-opt.active { color: var(--on-accent); }

.lang-thumb {
  position: absolute;
  top: 3px;
  bottom: 3px;
  left: 3px;
  width: 34px;
  border-radius: 999px;
  background: var(--accent);
  transition: transform 0.35s cubic-bezier(0.16, 1, 0.3, 1),
    width 0.35s cubic-bezier(0.16, 1, 0.3, 1);
}
.lang-switch.no-anim .lang-thumb { transition: none; }

/* Theme toggle */
.icon-btn {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  flex: none;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--surface);
  color: var(--text-2);
  cursor: pointer;
  transition: color 0.2s, border-color 0.2s, transform 0.2s;
}
.icon-btn:hover { color: var(--accent-text); border-color: var(--accent-2); transform: rotate(15deg); }
.icon-btn svg { width: 16px; height: 16px; }
.ico-sun { display: none; }
[data-theme="dark"] .ico-sun { display: block; }
[data-theme="dark"] .ico-moon { display: none; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding: 176px 0 120px;
  overflow: clip;
}
.hero::before,
.hero::after {
  content: "";
  position: absolute;
  border-radius: 50%;
  pointer-events: none;
  z-index: -1;
}
.hero::before {
  top: -240px;
  right: -170px;
  width: 660px;
  height: 660px;
  background: radial-gradient(
    circle at 35% 35%,
    color-mix(in oklab, var(--accent) 26%, transparent),
    transparent 66%
  );
}
.hero::after {
  bottom: -300px;
  left: -220px;
  width: 560px;
  height: 560px;
  background: radial-gradient(
    circle at 60% 40%,
    color-mix(in oklab, var(--accent-2) 18%, transparent),
    transparent 68%
  );
}

.hero h1 {
  margin: 18px 0 12px;
  font-size: clamp(3rem, 8vw, 4.75rem);
  font-weight: 700;
  line-height: 1.06;
  letter-spacing: -0.025em;
}

.hero-role {
  font-size: clamp(1.02rem, 2.4vw, 1.25rem);
  color: var(--text-2);
  font-weight: 500;
}

.hero-bio {
  max-width: 58ch;
  margin: 22px 0 36px;
  color: var(--muted);
  font-size: 1.02rem;
}
.hero-bio em { font-style: normal; color: var(--text-2); }

.hero-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.scroll-hint {
  position: absolute;
  left: 50%;
  bottom: 26px;
  transform: translateX(-50%);
  color: var(--muted);
  opacity: 0.75;
  animation: hint-float 2.4s ease-in-out infinite;
}
.scroll-hint svg { width: 22px; height: 22px; }
@keyframes hint-float {
  0%, 100% { transform: translate(-50%, 0); }
  50% { transform: translate(-50%, 7px); }
}

/* ---------- Buttons / chips ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: 999px;
  font-size: 14.5px;
  font-weight: 500;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.25s,
    background-color 0.2s, border-color 0.2s, color 0.2s;
}
.btn svg { width: 15px; height: 15px; }
.btn-primary {
  background: var(--accent);
  color: var(--on-accent);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}
.btn-ghost {
  background: var(--surface);
  border-color: var(--line);
  color: var(--text-2);
}
.btn-ghost:hover {
  color: var(--accent-text);
  border-color: var(--accent-2);
  transform: translateY(-2px);
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 30px;
  list-style: none;
}
.chips li {
  padding: 6px 15px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface);
  font-size: 13.5px;
  color: var(--text-2);
  transition: color 0.2s, border-color 0.2s, transform 0.2s;
}
.chips li:hover {
  color: var(--accent-text);
  border-color: var(--accent-2);
  transform: translateY(-2px);
}

/* ---------- Sections ---------- */
.section {
  border-top: 1px solid var(--line-soft);
  padding: 96px 0;
  transition: border-color 0.35s ease;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--accent-text);
  margin-bottom: 10px;
}

.section h2 {
  font-size: clamp(1.6rem, 3.4vw, 2.05rem);
  font-weight: 700;
  letter-spacing: -0.015em;
  line-height: 1.3;
}

.section-lead {
  margin: 14px 0 48px;
  color: var(--muted);
  max-width: 60ch;
}

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: transform 0.35s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.35s,
    border-color 0.35s, background-color 0.35s ease;
}

/* ---------- About ---------- */
.about-text {
  max-width: 72ch;
  color: var(--text-2);
  display: grid;
  gap: 16px;
  font-size: 1.03rem;
}
.about-text em { font-style: italic; }

/* ---------- Timeline ---------- */
.timeline {
  position: relative;
  padding-left: 26px;
  max-width: 760px;
}
.timeline::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 10px;
  bottom: 10px;
  width: 2px;
  background: linear-gradient(var(--line) 60%, transparent);
  border-radius: 2px;
}

.t-item { position: relative; padding: 0 0 44px 22px; }
.t-item:last-child { padding-bottom: 4px; }
.t-item::before {
  content: "";
  position: absolute;
  left: -26px;
  top: 7px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 2px solid var(--accent-2);
  background: var(--bg);
  transition: background-color 0.35s ease;
}
.t-item:first-child::before {
  background: var(--accent);
  border-color: var(--accent);
  box-shadow: 0 0 0 5px var(--accent-soft);
}

.t-period {
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  color: var(--muted);
}
.t-title { font-size: 17px; font-weight: 600; margin: 6px 0 2px; }
.t-org { font-size: 14px; color: var(--accent-text); font-weight: 500; }
.t-desc {
  margin-top: 8px;
  font-size: 14.8px;
  color: var(--text-2);
  max-width: 66ch;
}
.t-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 12px;
  list-style: none;
}
.t-tags li {
  padding: 3px 11px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-text);
  font-size: 12.5px;
  font-weight: 500;
}

/* ---------- Research ---------- */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
}
.interest { padding: 26px 24px; }
.interest h3 { font-size: 16px; font-weight: 600; margin-bottom: 8px; }
.interest p { font-size: 14.3px; color: var(--muted); }
.interest:hover {
  transform: translateY(-4px);
  border-color: var(--accent-2);
  border-color: color-mix(in oklab, var(--accent-2) 45%, var(--line));
  box-shadow: var(--shadow);
}

.subhead {
  margin: 56px 0 8px;
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.pubs { list-style: none; }
.pub {
  padding: 22px 4px;
  border-bottom: 1px solid var(--line-soft);
}
.pub:last-child { border-bottom: none; }
.pub-title {
  font-size: 16px;
  font-weight: 600;
  background-image: linear-gradient(var(--accent-2), var(--accent-2));
  background-repeat: no-repeat;
  background-position: 0 100%;
  background-size: 0% 2px;
  transition: color 0.25s ease,
    background-size 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  padding-bottom: 2px;
}
.pub-title:hover { color: var(--accent-text); background-size: 100% 2px; }
.pub-authors { margin-top: 6px; font-size: 14px; color: var(--text-2); }
.pub-authors strong { color: var(--text); font-weight: 600; }
.pub-authors .me {
  font-weight: 700;
  border-bottom: 2px solid var(--accent-2);
  padding-bottom: 1px;
}
.pub-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 14px;
  margin-top: 8px;
  font-size: 13px;
}
.venue {
  padding: 3px 11px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 500;
}
.pub-links { display: flex; gap: 12px; }
.pub-links a {
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-size: 12.5px;
  border-bottom: 1px dashed transparent;
  transition: border-color 0.2s;
}
.pub-links a:hover { border-bottom-color: var(--accent-2); }

/* ---------- Projects ---------- */
.grid-projects {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: 18px;
}
.proj {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 26px 24px;
}
.proj:hover {
  transform: translateY(-5px);
  border-color: var(--accent-2);
  border-color: color-mix(in oklab, var(--accent-2) 45%, var(--line));
  box-shadow: var(--shadow-lg);
}
.proj-head h3 { font-size: 16.5px; font-weight: 600; }
.proj > p { font-size: 14.3px; color: var(--muted); flex: 1; }
.proj .t-tags { margin-top: auto; padding-top: 6px; }

.proj-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  padding-top: 14px;
  border-top: 1px dashed var(--line);
}
.proj-links a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-size: 12.5px;
  font-weight: 500;
  transition: color 0.2s;
}
.proj-links a:hover { color: var(--accent); }
.proj-links svg {
  width: 13px;
  height: 13px;
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}
.proj-links a:hover svg { transform: translate(2px, -2px); }

/* ---------- Contact ---------- */
.contact-inner { text-align: center; }
.contact-inner .eyebrow { margin-bottom: 10px; }
.contact-lead {
  margin: 18px auto 36px;
  color: var(--muted);
  max-width: 46ch;
  font-size: 1.02rem;
}
.contact-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 12px;
}
.email-copy .email-text { font-family: var(--font-mono); font-size: 13.5px; }
.email-copy.copied { background: var(--accent-text); }

/* ---------- Footer ---------- */
footer {
  border-top: 1px solid var(--line-soft);
  padding: 30px 0 38px;
  transition: border-color 0.35s ease;
}
.foot-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 8px 24px;
  font-size: 13.5px;
  color: var(--muted);
}

/* ---------- Reveal on scroll (JS only) ---------- */
.js .reveal {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.85s cubic-bezier(0.16, 1, 0.3, 1),
    transform 0.85s cubic-bezier(0.16, 1, 0.3, 1);
  transition-delay: var(--reveal-delay, 0ms);
  will-change: opacity, transform;
}
.js .reveal.visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .js .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
  .scroll-hint { animation: none; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

/* ---------- Responsive ---------- */
@media (max-width: 760px) {
  .nav-links { display: none; }
  .hero { padding: 140px 0 96px; }
  .section { padding: 72px 0; }
  .hero-bio { margin-bottom: 30px; }
  .t-item { padding-bottom: 36px; }
  .scroll-hint { display: none; }
}