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

:root {
  --bg: #fafaf9;
  --bg-alt: #f5f5f4;
  --text: #1c1917;
  --text-muted: #78716c;
  --text-light: #a8a29e;
  --accent: #0c4a6e;
  --accent-light: #0369a1;
  --border: #e7e5e4;
  --radius: 6px;
  --max-width: 820px;
}

html {
  scroll-behavior: smooth;
  font-size: 17px;
}

body {
  font-family: 'Source Serif 4', 'Noto Serif SC', Georgia, 'Times New Roman', serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(250,250,249,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}

.site-logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
  text-decoration: none;
}

nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.15s;
}
nav a:hover { color: var(--text); text-decoration: none; }

.lang-switch a {
  padding: 0.25rem 0.625rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.8rem;
}
.lang-switch a:hover { border-color: var(--text-muted); }

/* Hero */
.hero {
  padding: 5rem 0 3.5rem;
  text-align: center;
}

.hero h1 {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
}

.subtitle {
  font-size: 1.15rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
  font-weight: 400;
}

.contact-info {
  display: flex;
  justify-content: center;
  gap: 2rem;
  flex-wrap: wrap;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.contact-item svg { flex-shrink: 0; }

/* Sections */
.section {
  padding: 4rem 0;
}

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

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 2rem;
  letter-spacing: -0.01em;
  font-variant: small-caps;
  position: relative;
  padding-bottom: 0.75rem;
}
.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 3rem;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
}

/* Entries */
.entry {
  margin-bottom: 2.5rem;
}
.entry:last-child { margin-bottom: 0; }

.entry-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  margin-bottom: 0.5rem;
}
.entry-header h3 {
  font-size: 1.1rem;
  font-weight: 600;
}
.entry-sub {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-top: 0.15rem;
}
.entry-detail {
  font-size: 0.875rem;
  color: var(--text-muted);
}
.entry-date {
  font-size: 0.85rem;
  color: var(--text-light);
  white-space: nowrap;
  padding-top: 0.15rem;
}

.entry ul {
  list-style: none;
  padding: 0;
}
.entry ul li {
  position: relative;
  padding-left: 1.25rem;
  margin-bottom: 0.35rem;
  font-size: 0.95rem;
  color: #44403c;
}
.entry ul li::before {
  content: '–';
  position: absolute;
  left: 0;
  color: var(--text-light);
}

.entry h4 {
  font-size: 0.95rem;
  font-weight: 600;
  margin: 1rem 0 0.5rem;
}

.doi-link {
  font-size: 0.85rem;
  color: var(--text-muted);
  word-break: break-all;
}
.doi-link:hover { color: var(--accent-light); }

.citation {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-style: italic;
  margin-top: 0.25rem;
}

/* Skills Grid */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 1.5rem;
}

.skill-category h4 {
  font-size: 0.9rem;
  font-weight: 600;
  font-variant: small-caps;
  color: var(--accent);
  margin-bottom: 0.4rem;
}
.skill-category p {
  font-size: 0.95rem;
  color: #44403c;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 2rem 0;
  text-align: center;
}
.footer-inner p {
  font-size: 0.8rem;
  color: var(--text-light);
  line-height: 1.8;
}

/* Responsive */
@media (max-width: 640px) {
  html { font-size: 16px; }
  .hero { padding: 3rem 0 2rem; }
  .hero h1 { font-size: 2rem; }
  nav { gap: 0.75rem; }
  nav a { font-size: 0.8rem; }
  .entry-header { flex-direction: column; }
  .entry-date { padding-top: 0; }
  .skills-grid { grid-template-columns: 1fr; }
  .section { padding: 2.5rem 0; }
}