/* ============================================================
   Design tokens
   ============================================================ */
:root {
  /* Light-mode colours */
  --color-bg:        #ffffff;
  --color-surface:   #f7f7f7;
  --color-text:      #1a1a1a;
  --color-text-muted:#5f5f5f;
  --color-accent:    #0055cc;
  --color-accent-hover: #0044aa;
  --color-border:    #e0e0e0;
  --color-tag-bg:    #e8f0fd;
  --color-tag-text:  #0055cc;

  /* Typography */
  --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
          Helvetica, Arial, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;

  /* Layout */
  --max-width:   760px;
  --nav-height:  56px;
  --radius:      6px;

  /* Transitions */
  --t-theme: background-color 0.18s ease, color 0.18s ease,
             border-color 0.18s ease;
}

/* Dark via OS preference (applies when not explicitly forced to light) */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg:        #0d0d0d;
    --color-surface:   #181818;
    --color-text:      #e6e6e6;
    --color-text-muted:#8a8a8a;
    --color-accent:    #5b9cf6;
    --color-accent-hover: #7ab3ff;
    --color-border:    #2a2a2a;
    --color-tag-bg:    #1a2640;
    --color-tag-text:  #5b9cf6;
  }
}

/* Dark forced by user toggle */
[data-theme="dark"] {
  --color-bg:        #0d0d0d;
  --color-surface:   #181818;
  --color-text:      #e6e6e6;
  --color-text-muted:#8a8a8a;
  --color-accent:    #5b9cf6;
  --color-accent-hover: #7ab3ff;
  --color-border:    #2a2a2a;
  --color-tag-bg:    #1a2640;
  --color-tag-text:  #5b9cf6;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.65;
  transition: var(--t-theme);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.15s ease;
}

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

/* ============================================================
   Navigation
   ============================================================ */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  transition: var(--t-theme);
}

/* Slight blur glass effect where supported */
@supports (backdrop-filter: blur(8px)) {
  header {
    background-color: color-mix(in srgb, var(--color-bg) 85%, transparent);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
  }
}

#main-nav {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  height: var(--nav-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.nav-name {
  font-weight: 600;
  font-size: 1rem;
  color: var(--color-text);
  white-space: nowrap;
  flex-shrink: 0;
}
.nav-name:hover { text-decoration: none; color: var(--color-accent); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: nowrap;
}

.nav-links a {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}
.nav-links a:hover { color: var(--color-accent); text-decoration: none; }

/* Theme toggle button */
#theme-toggle {
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  cursor: pointer;
  padding: 0.25rem 0.55rem;
  font-size: 0.85rem;
  line-height: 1;
  color: var(--color-text-muted);
  transition: border-color 0.15s ease, color 0.15s ease;
  flex-shrink: 0;
}
#theme-toggle:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

/* Show sun in dark mode, moon in light mode */
.icon-sun { display: none; }
.icon-moon { display: inline; }

[data-theme="dark"] .icon-sun,
:root:not([data-theme="light"]) .icon-sun {
  display: inline;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .icon-moon { display: none; }
}

[data-theme="dark"] .icon-moon { display: none; }

/* ============================================================
   Main content wrapper
   ============================================================ */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

section {
  padding: 3.5rem 0;
}

section + section {
  border-top: 1px solid var(--color-border);
}

/* ============================================================
   About section
   ============================================================ */
.about-header {
  margin-bottom: 1.25rem;
}

.about-header h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
}

.about-title {
  font-size: 1rem;
  color: var(--color-text-muted);
  margin-top: 0.25rem;
}

.about-institution {
  font-size: 1rem;
  margin-top: 0.15rem;
}

.about-bio {
  margin-top: 1.25rem;
  font-size: 1rem;
  line-height: 1.75;
  color: var(--color-text);
  max-width: 62ch;
}

.about-bio p + p {
  margin-top: 0.75rem;
}

/* Research interest tags */
.research-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 1.25rem;
}

.tag {
  background-color: var(--color-tag-bg);
  color: var(--color-tag-text);
  border-radius: 999px;
  padding: 0.2rem 0.75rem;
  font-size: 0.8125rem;
  font-weight: 500;
  white-space: nowrap;
  transition: var(--t-theme);
}

/* Social / contact links */
.contact-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.5rem;
  align-items: center;
}

.contact-links a {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}
.contact-links a:hover { color: var(--color-accent); text-decoration: none; }

.contact-links .contact-sep {
  color: var(--color-border);
  user-select: none;
}

/* ============================================================
   Publications section
   ============================================================ */
#publications h2 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 2rem;
}

.pub-year-group {
  margin-bottom: 2.25rem;
}

.pub-year-heading {
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 0.4rem;
  margin-bottom: 1rem;
}

.pub-item {
  margin-bottom: 1.25rem;
  padding-left: 0.875rem;
  border-left: 2px solid transparent;
  transition: border-color 0.15s ease;
}
.pub-item:hover {
  border-left-color: var(--color-accent);
}

.pub-title {
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1.45;
}

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

.pub-meta {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-top: 0.2rem;
  line-height: 1.5;
}

/* Loading / error states */
.pub-loading,
.pub-error {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

/* ============================================================
   Footer
   ============================================================ */
footer {
  border-top: 1px solid var(--color-border);
  padding: 2rem 1.5rem;
  text-align: center;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  transition: var(--t-theme);
}

footer p + p {
  margin-top: 0.25rem;
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 600px) {
  #main-nav {
    padding: 0 1rem;
  }

  .nav-links { gap: 0.6rem; }
  .nav-links a { font-size: 0.8rem; }

  main { padding: 0 1rem; }

  .about-header h1 { font-size: 1.6rem; }

  footer { padding: 1.5rem 1rem; }
}