:root {
  --bg: #0b0c0e;
  --bg-elevated: #12141a;
  --surface: #181b22;
  --surface-h: #22262f;
  --fg: #e8e6e1;
  --muted: #8b8d93;
  --subtle: #5c5e66;
  --accent: #7eb8da;
  --accent-fg: #0b0c0e;
  --border: #2a2d36;
  --border-s: #3d424e;
  --exception: #c4a574;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  min-height: 100vh;
}

header {
  padding: 1.5rem 1.5rem 0.5rem;
  text-align: center;
}
header h1 { margin: 0 0 0.25rem; font-size: 1.8rem; letter-spacing: 0.02em; }
.subtitle { margin: 0; color: var(--muted); font-size: 0.9rem; }

.loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  padding: 4rem 1rem;
  color: var(--muted);
}
.spinner {
  width: 36px; height: 36px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.9s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

main {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 1rem 2rem;
}

.controls {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.9rem;
  margin-bottom: 1rem;
}
.control-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.6rem;
}
.control-row:last-child { margin-bottom: 0; }

input[type="text"] {
  flex: 1 1 260px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--fg);
  padding: 0.5rem 0.7rem;
  border-radius: 6px;
  font-size: 0.95rem;
}
input[type="range"] { flex: 1 1 160px; accent-color: var(--accent); }

button {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--fg);
  padding: 0.5rem 0.8rem;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.9rem;
}
button:hover { background: var(--surface-h); border-color: var(--border-s); }
button:disabled { opacity: 0.5; cursor: not-allowed; }

.seg { display: flex; border: 1px solid var(--border); border-radius: 6px; overflow: hidden; }
.seg-btn { border: none; border-right: 1px solid var(--border); border-radius: 0; }
.seg-btn:last-child { border-right: none; }
.seg-btn.active { background: var(--accent); color: var(--accent-fg); font-weight: 600; }

#sliderLabel { color: var(--muted); font-size: 0.85rem; min-width: 70px; text-align: right; }

.info {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem;
  margin-bottom: 1rem;
}
.info-main { display: flex; gap: 1rem; align-items: center; }
.symbol {
  font-size: 2.6rem;
  font-weight: 700;
  width: 84px; height: 84px;
  display: flex; align-items: center; justify-content: center;
  background: var(--surface);
  border: 1px solid var(--border-s);
  border-radius: 10px;
  flex-shrink: 0;
}
.name-row { display: flex; gap: 0.6rem; align-items: baseline; flex-wrap: wrap; }
.name-row #infoName { font-size: 1.2rem; font-weight: 600; }
.name-row #infoZ, .name-row #infoCategory { color: var(--muted); font-size: 0.85rem; }
.config { font-size: 1.1rem; margin-top: 0.3rem; letter-spacing: 0.02em; }
.condensed { color: var(--accent); margin-top: 0.15rem; }
.stats { margin-top: 0.3rem; color: var(--muted); font-size: 0.85rem; display: flex; gap: 0.6rem; align-items: center; }
.exception-badge {
  background: var(--exception);
  color: var(--accent-fg);
  padding: 0.1rem 0.5rem;
  border-radius: 4px;
  font-weight: 600;
  font-size: 0.75rem;
}
.description { margin: 0.8rem 0 0; color: var(--fg); font-size: 0.9rem; line-height: 1.4; }
.diff { margin: 0.5rem 0 0; color: var(--exception); font-size: 0.85rem; }

.views {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem;
  min-height: 420px;
}
.view-panel { display: none; }
.view-panel.active { display: block; }

#atomCanvas { display: block; margin: 0 auto; max-width: 100%; height: auto; }

.fill-order-list { display: flex; flex-direction: column; gap: 0.5rem; }
.fill-row { display: flex; align-items: center; gap: 0.6rem; }
.fill-label { width: 44px; font-weight: 600; }
.fill-bar-track { flex: 1; background: var(--surface); border: 1px solid var(--border); border-radius: 4px; height: 18px; overflow: hidden; }
.fill-bar-fill { height: 100%; background: var(--accent); }
.fill-count { width: 60px; text-align: right; color: var(--muted); font-size: 0.85rem; }

.orbital-boxes { display: flex; flex-direction: column; gap: 0.7rem; }
.orbital-row { display: flex; align-items: center; gap: 0.6rem; flex-wrap: wrap; }
.orbital-row .fill-label { width: 44px; }
.orbital-box {
  width: 34px; height: 34px;
  border: 1px solid var(--border-s);
  border-radius: 4px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem;
  background: var(--surface);
  gap: 1px;
}
.orbital-box span { line-height: 1; }
.orbital-box.active { border-color: var(--accent); }

.periodic-table {
  display: grid;
  grid-template-columns: repeat(18, minmax(26px, 1fr));
  gap: 2px;
  font-size: 0.65rem;
}
.pt-cell {
  aspect-ratio: 1;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 3px;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  cursor: pointer;
  color: var(--fg);
  padding: 1px;
}
.pt-cell:hover { background: var(--surface-h); }
.pt-cell.selected { outline: 2px solid var(--accent); background: var(--surface-h); }
.pt-cell.exception { color: var(--exception); }
.pt-cell .pt-z { font-size: 0.55rem; color: var(--muted); }
.pt-cell.selected .pt-z { color: var(--accent-fg); }
.pt-blank { visibility: hidden; }

footer { text-align: center; color: var(--subtle); font-size: 0.8rem; padding: 1rem; }
footer a { color: var(--accent); }

@media (max-width: 640px) {
  .periodic-table { grid-template-columns: repeat(18, minmax(18px, 1fr)); font-size: 0.5rem; }
}