/* ==========================================================================
   Vu Nguyen — personal academic site
   Dependency-free stylesheet (no Bootstrap / no jQuery). Light + dark themes.
   ========================================================================== */

:root {
  --bg: #ffffff;
  --bg-soft: #f6f8fa;
  --bg-card: #ffffff;
  --text: #1f2328;
  --text-soft: #57606a;
  --border: #d9dee3;
  --accent: #0b69c7;
  --accent-soft: #e7f0fb;
  --accent-contrast: #ffffff;
  --danger: #b42318;
  --danger-soft: #fdecea;
  --success: #1a7f37;
  --success-soft: #e7f4ea;
  --warning: #9a6700;
  --warning-soft: #fcf3da;
  --shadow: 0 1px 3px rgba(27, 31, 36, 0.08), 0 1px 2px rgba(27, 31, 36, 0.06);
  --radius: 10px;
  --maxw: 980px;
}

html[data-theme="dark"] {
  --bg: #0d1117;
  --bg-soft: #161b22;
  --bg-card: #161b22;
  --text: #e6edf3;
  --text-soft: #9aa6b2;
  --border: #2d333b;
  --accent: #58a6ff;
  --accent-soft: #16263d;
  --accent-contrast: #0d1117;
  --danger: #ff7b72;
  --danger-soft: #2d1b1a;
  --success: #3fb950;
  --success-soft: #16261b;
  --warning: #d29922;
  --warning-soft: #2a2113;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica,
    Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  transition: background 0.2s ease, color 0.2s ease;
}

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

img { max-width: 100%; }

/* -------- Top navigation ------------------------------------------------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-nav .nav-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1.2rem;
}
.nav-brand {
  font-weight: 700;
  color: var(--text);
  margin-right: auto;
  font-size: 1.05rem;
}
.nav-brand:hover { text-decoration: none; color: var(--accent); }
.nav-links { display: flex; gap: 0.25rem; align-items: center; }
.nav-links a {
  color: var(--text-soft);
  padding: 0.4rem 0.7rem;
  border-radius: 6px;
  font-weight: 500;
}
.nav-links a:hover { background: var(--bg-soft); color: var(--text); text-decoration: none; }
.nav-links a.active { color: var(--accent); background: var(--accent-soft); }

.theme-toggle {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  width: 36px; height: 36px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 1.05rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s ease;
}
.theme-toggle:hover { background: var(--bg-soft); }

.nav-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  width: 36px; height: 36px;
  border-radius: 8px;
  cursor: pointer;
}

/* -------- Layout --------------------------------------------------------- */
.container {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 2rem 1.2rem 4rem;
}

h1, h2, h3, h4, h5 { line-height: 1.25; color: var(--text); }
h2 {
  font-size: 1.5rem;
  margin-top: 2.5rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border);
}
h3 { font-size: 1.2rem; margin-top: 1.8rem; color: var(--accent); }
h4 { font-size: 1.1rem; margin-top: 1.6rem; }

/* -------- Profile header ------------------------------------------------- */
.profile {
  display: flex;
  gap: 1.8rem;
  align-items: center;
  flex-wrap: wrap;
}
.profile-photo {
  width: 168px;
  height: 168px;
  object-fit: cover;
  border-radius: 50%;
  border: 3px solid var(--border);
  box-shadow: var(--shadow);
  flex-shrink: 0;
}
.profile-body { flex: 1; min-width: 260px; }
.profile-body h1 { margin: 0 0 0.2rem; font-size: 2rem; }
.profile-role { color: var(--text-soft); font-size: 1.05rem; margin: 0 0 0.8rem; }

.social-row { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.6rem; }
.social-row a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text);
  font-size: 0.9rem;
  background: var(--bg-card);
}
.social-row a:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }
.social-row svg { width: 16px; height: 16px; fill: currentColor; }

/* -------- Generic prose lists ------------------------------------------- */
.container ul { padding-left: 1.3rem; }
.container li { margin: 0.35rem 0; }

/* -------- News feed ------------------------------------------------------ */
.news {
  max-height: 560px;
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-soft);
  padding: 0.5rem 1.2rem;
}
.news ul { list-style: none; padding-left: 0; }
.news li {
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--border);
}
.news li:last-child { border-bottom: none; }
.news .date {
  display: inline-block;
  font-weight: 600;
  color: var(--accent);
  margin-right: 0.4rem;
}

/* -------- Publications (legacy bootstrap-class compatibility) ------------ */
.media {
  display: flex;
  gap: 1.2rem;
  padding: 1.1rem;
  margin: 1rem 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-card);
  box-shadow: var(--shadow);
}
.media:hover { border-color: var(--accent); }
.pull-left { flex-shrink: 0; }
.media .thumbnail,
.media a.pull-left {
  display: block;
  width: 96px;
}
.media img {
  width: 96px;
  height: 96px;
  object-fit: contain;
  border-radius: 14px;
}
.media-body { flex: 1; min-width: 0; }
.media-body strong { color: var(--text); }

/* Labels / badges (replaces Bootstrap .label) */
.label {
  display: inline-block;
  padding: 0.18em 0.6em;
  margin: 0.15rem 0.15rem 0.15rem 0;
  font-size: 0.78rem;
  font-weight: 600;
  border-radius: 999px;
  white-space: nowrap;
  border: 1px solid transparent;
}
.label:hover { text-decoration: none; opacity: 0.9; }
.label-default { background: var(--bg-soft); color: var(--text-soft); border-color: var(--border); cursor: pointer; }
.label-info    { background: var(--accent-soft); color: var(--accent); }
.label-success { background: var(--success-soft); color: var(--success); }
.label-danger  { background: var(--danger-soft); color: var(--danger); }
.label-warning { background: var(--warning-soft); color: var(--warning); }

/* -------- Modal (abstract pop-ups), Bootstrap-free ----------------------- */
.modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 100;
  background: rgba(0, 0, 0, 0.55);
  padding: 1.5rem;
  overflow-y: auto;
}
.modal.open { display: flex; align-items: flex-start; justify-content: center; }
.modal-dialog { width: 100%; max-width: 680px; margin: 4vh auto; }
.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
  overflow: hidden;
}
.modal-header {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1rem 1.2rem;
  border-bottom: 1px solid var(--border);
}
.modal-title { margin: 0; font-size: 1.15rem; }
.modal-body { padding: 1.2rem; color: var(--text); text-align: justify; }
.modal .close {
  margin-left: auto;
  background: transparent;
  border: none;
  font-size: 1.6rem;
  line-height: 1;
  color: var(--text-soft);
  cursor: pointer;
}
.modal .close:hover { color: var(--text); }

/* -------- Footer --------------------------------------------------------- */
.site-footer {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 2rem 1.2rem 3rem;
  border-top: 1px solid var(--border);
  color: var(--text-soft);
  font-size: 0.9rem;
  text-align: center;
}

/* -------- Responsive ----------------------------------------------------- */
@media (max-width: 720px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    right: 0.8rem;
    flex-direction: column;
    align-items: stretch;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 0.4rem;
    min-width: 180px;
    box-shadow: var(--shadow);
  }
  .nav-links.open { display: flex; }
  .nav-toggle { display: inline-flex; align-items: center; justify-content: center; }
  .profile { justify-content: center; text-align: center; }
  .social-row { justify-content: center; }
  .media { flex-direction: row; }
}