.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 44px;
  width: 44px;
  height: 44px;
  padding: 10px;
  border: 0;
  border-radius: 50%;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
}
.theme-toggle[hidden] { display: none; }
.theme-toggle:hover { background: var(--hover); }
.theme-toggle svg { width: 21px; height: 21px; fill: none; stroke: currentColor; stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }
.theme-sun { display: none; }
[data-theme="dark"] .theme-sun { display: block; }
[data-theme="dark"] .theme-moon { display: none; }

@media screen {
  :root[data-theme="dark"] {
    color-scheme: dark;
    --paper: #191e24;
    --grid: #252b33;
    --ink: #ede9e2;
    --muted: #b4bbc4;
    --line: #3b434d;
    --rule: #596675;
    --surface: #222830;
    --shadow: #12171c;
    --hover: #303b48;
    --plum: #a9cde8;
    --link: #a9cde8;
    --highlight: #354352;
    --highlight-edge: #8bacc8;
  }
  [data-theme="dark"] #research .paper { background: var(--surface); border-color: var(--line); }
  [data-theme="dark"] #research .paper-meta .venue-detail { background: #303943; }
  [data-theme="dark"] #research .paper-resources { border-color: var(--line); }
  [data-theme="dark"] .opportunity { background: #443b22; border-left-color: #d1aa48; }
  [data-theme="dark"] .institution-logo.hkust { background: #fdfdfc; }
}
@media print { .theme-toggle { display: none; } }