:root {
  --bg: #fafafa;
  --bg-panel: #ffffff;
  --fg: #1a1a1a;
  --fg-muted: #666;
  --border: #ddd;
  --accent: #0d6efd;
  --accent-fg: #fff;
  --error: #b00020;
  --success: #2e7d32;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1a1a1a;
    --bg-panel: #242424;
    --fg: #e8e8e8;
    --fg-muted: #999;
    --border: #3a3a3a;
    --accent: #4a9eff;
    --accent-fg: #fff;
    --error: #ff6b6b;
    --success: #66bb6a;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  font-size: 14px;
  line-height: 1.45;
}

main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem;
}

header {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.5rem;
  margin-bottom: 1rem;
}
header h1 { font-size: 1.4rem; margin: 0; }
header .tag { color: var(--fg-muted); font-size: 0.85rem; }

.panels {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
@media (max-width: 800px) {
  .panels { grid-template-columns: 1fr; }
}

.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.75rem;
}
.panel h2 {
  font-size: 1rem;
  margin: 0 0 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.panel .panel-actions {
  margin-left: auto;
  display: flex;
  gap: 0.25rem;
}

textarea {
  width: 100%;
  min-height: 14rem;
  font-family: var(--mono);
  font-size: 12px;
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.5rem;
  resize: vertical;
  tab-size: 8;
}
textarea.dragover {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, var(--bg));
}

input[type="number"], input[type="text"], select {
  font-family: var(--mono);
  font-size: 12px;
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.25rem 0.4rem;
}

button {
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.3rem 0.7rem;
  font-size: 0.85rem;
  cursor: pointer;
}
button:hover { background: color-mix(in srgb, var(--accent) 12%, var(--bg)); }
button.primary {
  background: var(--accent);
  color: var(--accent-fg);
  border-color: var(--accent);
}
button.primary:hover {
  filter: brightness(1.1);
}

.solve-bar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin: 1rem 0;
}
.solve-bar .status { color: var(--fg-muted); font-size: 0.85rem; }
.solve-bar .status.error { color: var(--error); }
.solve-bar .status.ok { color: var(--success); }

.spinner {
  display: inline-block;
  width: 1rem;
  height: 1rem;
  border: 2px solid color-mix(in srgb, var(--accent) 25%, transparent);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  vertical-align: middle;
}
button[disabled] {
  opacity: 0.65;
  cursor: progress;
}
@keyframes spin {
  to { transform: rotate(360deg); }
}

.options {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.75rem;
  margin-bottom: 1rem;
}
.options summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 0.95rem;
}
.options-group {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.4rem 1rem;
  margin-top: 0.6rem;
}
.options-group label {
  display: flex;
  flex-direction: column;
  font-size: 0.8rem;
  color: var(--fg-muted);
}
.options-group label > span:first-child { margin-bottom: 0.15rem; }
.options-group input[type="number"], .options-group select {
  font-size: 12px;
}
.options-group .check {
  flex-direction: row;
  align-items: center;
  gap: 0.4rem;
}
.preset-row {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

table.results {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--mono);
  font-size: 12px;
}
table.results th, table.results td {
  padding: 0.25rem 0.5rem;
  text-align: right;
  border-bottom: 1px solid var(--border);
}
table.results th { text-align: left; cursor: pointer; user-select: none; }
table.results th.num { text-align: right; }
table.results td.name { text-align: left; font-weight: 500; }
table.results tr.monomer { background: color-mix(in srgb, var(--accent) 5%, transparent); }

.diagnostics {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.4rem 1rem;
  font-size: 0.85rem;
  margin-bottom: 0.5rem;
}
.diagnostics .label { color: var(--fg-muted); }
.diagnostics .value { font-family: var(--mono); }

.chart-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin: 1rem 0;
}
@media (max-width: 800px) {
  .chart-row { grid-template-columns: 1fr; }
}
.chart-row .chart {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.5rem;
}

/* Standalone convergence chart (outside .chart-row) — keep compact. */
.convergence-chart {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.5rem;
  margin: 1rem 0;
  max-width: 360px;
}

.table-pagination {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin: 0.4rem 0 0;
  font-size: 0.85rem;
  color: var(--fg-muted);
}
.link-button {
  background: none;
  border: none;
  padding: 0;
  color: var(--accent);
  text-decoration: underline;
  cursor: pointer;
  font: inherit;
}

.error-box {
  border: 1px solid var(--error);
  background: color-mix(in srgb, var(--error) 8%, var(--bg-panel));
  color: var(--error);
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
  font-family: var(--mono);
  font-size: 12px;
  white-space: pre-wrap;
  margin: 1rem 0;
}

footer {
  margin-top: 2rem;
  font-size: 0.8rem;
  color: var(--fg-muted);
  border-top: 1px solid var(--border);
  padding-top: 0.5rem;
}
footer a { color: var(--accent); }