:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --border: #dde3ea;
  --text: #1a2233;
  --text-muted: #5b6577;
  --accent: #2f6fed;
  --accent-hover: #2559c7;
  --error: #d1373f;
  --radius: 10px;
  --shadow: 0 1px 3px rgba(20, 30, 50, 0.08), 0 1px 2px rgba(20, 30, 50, 0.06);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12151c;
    --surface: #1a1e28;
    --border: #2b3140;
    --text: #e7ebf3;
    --text-muted: #9aa4b8;
    --accent: #5b8dff;
    --accent-hover: #7ba0ff;
    --error: #ff6b6f;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(0, 0, 0, 0.3);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

.page {
  max-width: 860px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

.site-header {
  text-align: center;
  margin-bottom: 24px;
}

.site-header h1 {
  margin: 0 0 6px;
  font-size: 1.9rem;
  font-weight: 700;
}

.subtitle {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.tabs {
  display: flex;
  gap: 4px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 4px;
  margin-bottom: 20px;
  max-width: 320px;
  margin-left: auto;
  margin-right: auto;
}

.tab-btn {
  flex: 1;
  padding: 10px 16px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 7px;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.tab-btn:hover {
  color: var(--text);
}

.tab-btn.active {
  background: var(--accent);
  color: #fff;
}

.tab-panel {
  display: none;
}

.tab-panel.active {
  display: block;
}

.calc-form {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: flex-end;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}

.field {
  flex: 1 1 260px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.field-narrow {
  flex: 1 1 160px;
}

.field label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
}

.field input, .splitter select {
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 0.95rem;
  font-family: "SF Mono", "Cascadia Code", Consolas, monospace;
}

.field input:focus, .splitter select:focus {
  outline: none;
  border-color: var(--accent);
}

.calc-btn {
  padding: 10px 22px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
  height: 42px;
}

.calc-btn:hover {
  background: var(--accent-hover);
}

.calc-btn.secondary {
  background: var(--surface);
  color: var(--accent);
  border: 1px solid var(--border);
}

.calc-btn.secondary:hover {
  background: var(--bg);
}

.error-msg {
  color: var(--error);
  font-size: 0.9rem;
  margin: 12px 4px 0;
  font-weight: 600;
}

.results {
  margin-top: 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
}

.results-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px 20px;
}

.result {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
}

.result.wide {
  grid-column: 1 / -1;
}

.result .label {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--text-muted);
  font-weight: 600;
}

.result .value {
  font-size: 1rem;
  font-weight: 600;
  word-break: break-all;
}

.mono {
  font-family: "SF Mono", "Cascadia Code", Consolas, monospace;
  font-weight: 500;
  font-size: 0.92rem;
}

.splitter {
  margin-top: 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 4px 20px;
  box-shadow: var(--shadow);
}

.splitter summary {
  cursor: pointer;
  padding: 14px 0;
  font-weight: 600;
  font-size: 0.95rem;
}

.splitter-body {
  padding-bottom: 18px;
}

.splitter-controls {
  display: flex;
  gap: 10px;
  margin: 10px 0 16px;
}

.splitter select {
  flex: 1;
}

.table-wrap {
  overflow-x: auto;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-family: "SF Mono", "Cascadia Code", Consolas, monospace;
  font-size: 0.85rem;
}

th, td {
  text-align: left;
  padding: 8px 10px;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}

th {
  color: var(--text-muted);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.note {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin: 8px 0 0;
}

.site-footer {
  text-align: center;
  margin-top: 40px;
  color: var(--text-muted);
  font-size: 0.82rem;
}

@media (max-width: 480px) {
  .results-grid {
    grid-template-columns: 1fr;
  }
  .calc-btn {
    width: 100%;
  }
}