/* ============================================================
   Lea Yanhui Li — Personal Site v2
   Aesthetic: Precision-technical minimalism
   Fonts: Geist Mono (labels) + Newsreader (display) + system sans
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Newsreader:ital,wght@0,300;0,400;1,300;1,400&family=JetBrains+Mono:wght@300;400;500&display=swap');

/* ── Variables ─────────────────────────────────────────────── */
:root {
  /* Light theme */
  --bg:         #fafaf8;
  --surface:    #f4f3ef;
  --border:     #e3e1db;
  --border-2:   #ccc9c0;
  --ink:        #181816;
  --ink-2:      #44443f;
  --muted:      #8a8880;
  --accent:     #2d5016;
  --accent-dim: #3d6b20;
  --tag-bg:     #eceae4;
  --tag-text:   #6b6960;
  --code-bg:    #f0efe9;
  --white:      #ffffff;

  /* Active state */
  --active-dot: #4a7c2f;

  /* Type */
  --serif:  'Newsreader', Georgia, 'Times New Roman', serif;
  --mono:   'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
  --sans:   -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;

  /* Layout */
  --max-w:  780px;
  --nav-h:  56px;

  /* Transitions */
  --t:      0.18s ease;
}

[data-theme="dark"] {
  --bg:         #111110;
  --surface:    #1a1a18;
  --border:     #2a2a27;
  --border-2:   #3a3a36;
  --ink:        #f0efeb;
  --ink-2:      #c8c7c0;
  --muted:      #6a6a65;
  --accent:     #7ab648;
  --accent-dim: #8dc85a;
  --tag-bg:     #222220;
  --tag-text:   #888880;
  --code-bg:    #1e1e1c;
  --white:      #1a1a18;
}

/* ── Reset ──────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: var(--sans);
  background: var(--bg);
  color: var(--ink);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  transition: background var(--t), color var(--t);
}
img { max-width: 100%; display: block; }
a { color: var(--accent); text-decoration: none; transition: opacity var(--t); }
a:hover { opacity: 0.7; }

/* ── Typography ─────────────────────────────────────────────── */
h1, h2 { font-family: var(--serif); font-weight: 300; line-height: 1.15; }
h1 { font-size: clamp(2.2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.4rem, 3vw, 1.9rem); margin-bottom: 0.75rem; }
h3 { font-size: 1rem; font-weight: 500; line-height: 1.4; margin-bottom: 0.35rem; }
p  { color: var(--ink-2); margin-bottom: 1rem; font-size: 0.95rem; line-height: 1.75; }
p:last-child { margin-bottom: 0; }
code {
  font-family: var(--mono);
  font-size: 0.8rem;
  background: var(--code-bg);
  padding: 0.15em 0.4em;
  border-radius: 3px;
  color: var(--ink-2);
}

/* ── Layout ─────────────────────────────────────────────────── */
.container { max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem; }

/* ── Nav ─────────────────────────────────────────────────────── */
nav {
  position: sticky; top: 0; z-index: 200;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  height: var(--nav-h);
  transition: background var(--t), border-color var(--t);
}
.nav-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 100%;
  display: flex;
  align-items: center;
  gap: 1.5rem;
}
.nav-brand {
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 400;
  letter-spacing: 0.06em;
  color: var(--ink);
  text-decoration: none;
  white-space: nowrap;
  flex-shrink: 0;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  list-style: none;
  margin-left: auto;
}
.nav-links a {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  color: var(--muted);
  text-decoration: none;
  transition: color var(--t);
  white-space: nowrap;
}
.nav-links a:hover, .nav-links a.active { color: var(--ink); opacity: 1; }

/* Dark mode toggle */
.dark-toggle {
  background: none;
  border: 1px solid var(--border);
  cursor: pointer;
  padding: 0.3rem 0.55rem;
  border-radius: 4px;
  display: flex;
  align-items: center;
  gap: 0.3rem;
  font-family: var(--mono);
  font-size: 0.68rem;
  color: var(--muted);
  transition: all var(--t);
  flex-shrink: 0;
}
.dark-toggle:hover { color: var(--ink); border-color: var(--border-2); }
.dark-toggle .icon-sun  { display: none; }
.dark-toggle .icon-moon { display: inline; }
[data-theme="dark"] .dark-toggle .icon-sun  { display: inline; }
[data-theme="dark"] .dark-toggle .icon-moon { display: none; }

/* Mobile hamburger */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  flex-direction: column;
  gap: 4px;
  margin-left: auto;
}
.nav-toggle span {
  display: block; width: 20px; height: 1.5px;
  background: var(--ink); transition: all 0.25s;
}

/* ── Scroll reveal ───────────────────────────────────────────── */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}
.reveal.visible {
  opacity: 1;
  transform: none;
}

/* ── Hero ────────────────────────────────────────────────────── */
.hero {
  padding: 6rem 0 4.5rem;
  border-bottom: 1px solid var(--border);
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute;
  top: -60px; right: -80px;
  width: 400px; height: 400px;
  background: radial-gradient(circle, color-mix(in srgb, var(--accent) 8%, transparent) 0%, transparent 70%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 1.25rem;
}
.hero-badge::before {
  content: '';
  display: inline-block;
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--active-dot);
  animation: pulse 2.5s ease-in-out infinite;
}
@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50%       { opacity: 0.4; transform: scale(0.8); }
}

.hero h1 { margin-bottom: 0.6rem; }

.hero-subtitle {
  font-family: var(--mono);
  font-size: 0.82rem;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-wrap: wrap;
}
.hero-subtitle .dot { color: var(--border-2); }

.hero-secondary {
  font-size: 0.97rem;
  color: var(--ink-2);
  max-width: 520px;
  line-height: 1.75;
  margin-bottom: 2.25rem;
  font-weight: 400;
}

.hero-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  align-items: center;
}

/* ── Buttons ─────────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  padding: 0.55rem 1.1rem;
  border: 1px solid var(--border-2);
  color: var(--ink-2);
  background: transparent;
  text-decoration: none;
  transition: all var(--t);
  border-radius: 3px;
}
.btn:hover { background: var(--ink); color: var(--bg); border-color: var(--ink); opacity: 1; }
.btn-primary {
  background: var(--ink);
  color: var(--bg);
  border-color: var(--ink);
}
.btn-primary:hover { background: var(--accent); border-color: var(--accent); color: var(--white); }
.btn-ghost { border-color: transparent; padding-left: 0; color: var(--muted); }
.btn-ghost:hover { background: transparent; color: var(--ink); border-color: transparent; }

/* ── Section base ────────────────────────────────────────────── */
.section { padding: 3.5rem 0; border-bottom: 1px solid var(--border); }
.section:last-child { border-bottom: none; }

.section-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 2rem;
  flex-wrap: wrap;
  gap: 0.5rem;
}
.section-label {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}
.section-link {
  font-family: var(--mono);
  font-size: 0.68rem;
  color: var(--accent);
  letter-spacing: 0.04em;
}

/* ── Focus grid ──────────────────────────────────────────────── */
.focus-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  border-radius: 4px;
  overflow: hidden;
}
.focus-item {
  background: var(--bg);
  padding: 1.4rem 1.25rem;
  transition: background var(--t);
}
.focus-item:hover { background: var(--surface); }
.focus-item h3 {
  font-family: var(--mono);
  font-size: 0.73rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink);
  margin-bottom: 0.45rem;
  font-weight: 500;
}
.focus-item p { font-size: 0.88rem; color: var(--muted); margin: 0; line-height: 1.6; }

/* ── Experiment cards ────────────────────────────────────────── */
.exp-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}
.exp-card {
  border: 1px solid var(--border);
  padding: 1.25rem;
  border-radius: 4px;
  background: var(--surface);
  transition: border-color var(--t), transform var(--t);
  position: relative;
}
.exp-card:hover { border-color: var(--border-2); transform: translateY(-2px); }
.exp-card-num {
  font-family: var(--mono);
  font-size: 0.65rem;
  color: var(--muted);
  letter-spacing: 0.1em;
  margin-bottom: 0.6rem;
}
.exp-card h3 { font-size: 0.9rem; font-weight: 500; margin-bottom: 0.5rem; color: var(--ink); }
.exp-card p  { font-size: 0.83rem; color: var(--muted); line-height: 1.6; margin-bottom: 0.9rem; }
.exp-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.exp-status {
  font-family: var(--mono);
  font-size: 0.63rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.18rem 0.5rem;
  border-radius: 2px;
  background: var(--tag-bg);
  color: var(--tag-text);
}
.exp-status.active { background: color-mix(in srgb, var(--accent) 12%, transparent); color: var(--accent-dim); }
.exp-card-link {
  font-family: var(--mono);
  font-size: 0.68rem;
  color: var(--accent);
  text-decoration: none;
}
.exp-card-link:hover { opacity: 0.7; }

/* ── GitHub repos ────────────────────────────────────────────── */
.github-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
}
.repo-card {
  border: 1px solid var(--border);
  padding: 1.1rem 1.2rem;
  border-radius: 4px;
  background: var(--bg);
  transition: border-color var(--t);
  text-decoration: none;
  display: block;
}
.repo-card:hover { border-color: var(--accent); opacity: 1; }
.repo-name {
  font-family: var(--mono);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 0.35rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.repo-desc { font-size: 0.83rem; color: var(--muted); line-height: 1.55; margin-bottom: 0.75rem; }
.repo-meta {
  display: flex;
  gap: 1rem;
  font-family: var(--mono);
  font-size: 0.67rem;
  color: var(--muted);
  letter-spacing: 0.03em;
}
.repo-meta span { display: flex; align-items: center; gap: 0.25rem; }
.repo-loading, .repo-error {
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--muted);
  padding: 2rem 0;
  text-align: center;
  grid-column: 1/-1;
}
.repo-skeleton {
  border: 1px solid var(--border);
  padding: 1.1rem 1.2rem;
  border-radius: 4px;
  background: var(--surface);
  animation: shimmer 1.4s ease infinite;
}
@keyframes shimmer {
  0%, 100% { opacity: 0.6; }
  50%       { opacity: 1; }
}
.skel-line {
  height: 10px; border-radius: 3px;
  background: var(--border-2);
  margin-bottom: 0.6rem;
}
.skel-line.short { width: 55%; }
.skel-line.long  { width: 90%; }
.skel-line.med   { width: 70%; }

/* ── Projects ─────────────────────────────────────────────────── */
.project-list { display: flex; flex-direction: column; }
.project-card {
  padding: 2.25rem 0;
  border-bottom: 1px solid var(--border);
}
.project-card:first-child { padding-top: 0; }
.project-card:last-child  { border-bottom: none; }

.project-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.75rem;
}
.project-tag {
  font-family: var(--mono);
  font-size: 0.67rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.4rem;
}
.project-card h3 { font-size: 1.05rem; font-weight: 500; color: var(--ink); }
.project-card h3 a { color: inherit; }
.project-card h3 a:hover { color: var(--accent); opacity: 1; }
.project-card > p { font-size: 0.9rem; color: var(--ink-2); margin-bottom: 1.25rem; }

/* Architecture diagram */
.arch-diagram {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1.1rem 1.4rem;
  margin-bottom: 1.1rem;
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--ink-2);
  line-height: 1.8;
  overflow-x: auto;
}
.arch-node {
  display: inline-block;
  border: 1px solid var(--border-2);
  padding: 0.15rem 0.6rem;
  border-radius: 3px;
  background: var(--bg);
  color: var(--ink);
  font-size: 0.73rem;
}
.arch-arrow {
  color: var(--accent);
  margin: 0 0.4rem;
  font-size: 0.8rem;
}
.arch-row { margin-bottom: 0.2rem; display: flex; align-items: center; }

.tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 1rem;
}
.tech-tag {
  font-family: var(--mono);
  font-size: 0.68rem;
  padding: 0.2rem 0.55rem;
  background: var(--tag-bg);
  color: var(--tag-text);
  border-radius: 2px;
  letter-spacing: 0.03em;
}
.project-links { display: flex; gap: 0.6rem; flex-wrap: wrap; }

/* ── Writing posts ────────────────────────────────────────────── */
.post-list { display: flex; flex-direction: column; }
.post-item {
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--border);
  display: grid;
  grid-template-columns: 2.5rem 1fr;
  gap: 1.25rem;
}
.post-item:last-child { border-bottom: none; }
.post-num {
  font-family: var(--mono);
  font-size: 0.67rem;
  color: var(--muted);
  padding-top: 0.2rem;
}
.post-meta {
  font-family: var(--mono);
  font-size: 0.67rem;
  color: var(--muted);
  margin-bottom: 0.3rem;
}
.post-item h3 { font-size: 0.97rem; font-weight: 500; color: var(--ink); margin-bottom: 0.3rem; }
.post-item h3 a { color: inherit; }
.post-item p  { font-size: 0.85rem; color: var(--muted); margin: 0; line-height: 1.6; }

/* ── Experiment log (experiments.html) ───────────────────────── */
.exp-log { display: flex; flex-direction: column; }
.exp-entry {
  padding: 2.5rem 0;
  border-bottom: 1px solid var(--border);
  display: grid;
  grid-template-columns: 5rem 1fr;
  gap: 2rem;
}
.exp-entry:first-child { padding-top: 0; }
.exp-entry:last-child  { border-bottom: none; }
.exp-num {
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--muted);
  letter-spacing: 0.1em;
  padding-top: 0.2rem;
}
.exp-num .num-big {
  font-size: 1.6rem;
  color: var(--border-2);
  display: block;
  line-height: 1;
  margin-bottom: 0.25rem;
}
.exp-body h3 { font-size: 1.05rem; font-weight: 500; margin-bottom: 0.5rem; color: var(--ink); }
.exp-body p  { font-size: 0.88rem; color: var(--ink-2); margin-bottom: 0.75rem; }

.exp-meta-row {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin-bottom: 0.75rem;
}
.exp-meta-item {
  font-family: var(--mono);
  font-size: 0.68rem;
  color: var(--muted);
}
.exp-meta-item strong { color: var(--ink-2); font-weight: 500; }

.result-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 2px solid var(--accent);
  padding: 0.85rem 1.1rem;
  border-radius: 0 3px 3px 0;
  margin-bottom: 1rem;
}
.result-box p { font-size: 0.85rem; color: var(--ink-2); margin: 0; }

/* ── About page ──────────────────────────────────────────────── */
.about-layout {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: 3.5rem;
  padding: 3.5rem 0;
  border-bottom: 1px solid var(--border);
}
.about-photo-wrap { position: relative; }
.about-photo {
  width: 180px; height: 180px;
  object-fit: cover;
  filter: grayscale(15%);
  border: 1px solid var(--border);
  border-radius: 3px;
}
.about-photo-placeholder {
  width: 180px; height: 180px;
  background: var(--surface);
  border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--mono); font-size: 0.68rem;
  color: var(--muted); letter-spacing: 0.08em; text-align: center;
  border-radius: 3px;
}
.focus-list { list-style: none; margin: 1.25rem 0; }
.focus-list li {
  font-size: 0.9rem; color: var(--ink-2);
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 0.65rem;
}
.focus-list li::before { content: '↳'; font-family: var(--mono); color: var(--accent); font-size: 0.8rem; }

/* ── Page header ─────────────────────────────────────────────── */
.page-header {
  padding: 5rem 0 3rem;
  border-bottom: 1px solid var(--border);
}
.page-header h1 { margin-bottom: 0.6rem; }
.page-header p { font-size: 1rem; color: var(--muted); max-width: 460px; margin: 0; font-weight: 300; }

/* ── Footer ──────────────────────────────────────────────────── */
footer {
  padding: 2.5rem 0;
  border-top: 1px solid var(--border);
}
.footer-inner {
  max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem;
  display: flex; justify-content: space-between; align-items: center;
  flex-wrap: wrap; gap: 0.75rem;
}
.footer-copy { font-family: var(--mono); font-size: 0.68rem; color: var(--muted); }
.footer-links { display: flex; gap: 1.25rem; }
.footer-links a { font-family: var(--mono); font-size: 0.68rem; color: var(--muted); }
.footer-links a:hover { color: var(--ink); opacity: 1; }

/* ── Misc helpers ────────────────────────────────────────────── */
.divider { height: 1px; background: var(--border); margin: 2.5rem 0; }
.hero-eyebrow {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 1.5rem;
  display: flex; align-items: center; gap: 0.65rem;
}
.hero-eyebrow::before {
  content: ''; display: block; width: 24px; height: 1px;
  background: var(--accent);
}

/* ── Responsive ──────────────────────────────────────────────── */
@media (max-width: 700px) {
  .nav-links       { display: none; flex-direction: column; gap: 0; }
  .nav-links.open  {
    display: flex;
    position: absolute; top: var(--nav-h); left: 0; right: 0;
    background: var(--bg);
    padding: 0.5rem 1.5rem 1.25rem;
    border-bottom: 1px solid var(--border);
  }
  .nav-links li a  { display: block; padding: 0.65rem 0; border-bottom: 1px solid var(--border); }
  .dark-toggle     { display: none; }
  .nav-toggle      { display: flex; }

  .focus-grid  { grid-template-columns: 1fr 1fr; }
  .exp-cards   { grid-template-columns: 1fr; }
  .github-grid { grid-template-columns: 1fr; }
  .about-layout { grid-template-columns: 1fr; gap: 2rem; }
  .exp-entry   { grid-template-columns: 3.5rem 1fr; gap: 1rem; }
  .post-item   { grid-template-columns: 1fr; gap: 0; }
  .post-num    { display: none; }
  .hero { padding: 3.5rem 0 3rem; }
  .project-header { flex-direction: column; }
}
@media (max-width: 480px) {
  .focus-grid { grid-template-columns: 1fr; }
  h1 { font-size: 2rem; }
}