/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --primary:      #1c3d5a;
  --primary-light:#2a5a82;
  --accent:       #c9611f;
  --accent-light: #e8834a;
  --bg:           #f5f4f0;
  --card:         #ffffff;
  --border:       #ddd9d2;
  --text:         #222;
  --text-muted:   #666;
  --shaku-bg:     #eef4fb;
  --metric-bg:    #faf4ee;
  --radius:       10px;
  --shadow:       0 2px 8px rgba(0,0,0,0.08);
}

body {
  font-family: 'Hiragino Sans', 'Meiryo', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Header ===== */
header {
  background: var(--primary);
  color: #fff;
  padding: 20px 16px 18px;
  text-align: center;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}

header p {
  font-size: 0.85rem;
  opacity: 0.8;
  margin-top: 4px;
}

/* ===== Tabs ===== */
.tabs {
  display: flex;
  background: var(--primary);
  border-bottom: 3px solid var(--accent);
  padding: 0 8px;
  gap: 4px;
}

.tab {
  flex: 1;
  padding: 10px 8px;
  background: transparent;
  border: none;
  color: rgba(255,255,255,0.65);
  font-size: 0.95rem;
  font-family: inherit;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  margin-bottom: -3px;
  transition: color 0.15s, border-color 0.15s;
}

.tab:hover {
  color: rgba(255,255,255,0.9);
}

.tab.active {
  color: #fff;
  border-bottom-color: var(--accent);
  font-weight: 600;
}

/* ===== Main layout ===== */
main {
  max-width: 860px;
  margin: 0 auto;
  padding: 16px 12px 40px;
}

.tab-content {
  display: none;
  flex-direction: column;
  gap: 16px;
}

.tab-content.active {
  display: flex;
}

/* ===== Card ===== */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 16px;
  box-shadow: var(--shadow);
}

.card h2 {
  font-size: 1rem;
  color: var(--primary);
  margin-bottom: 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

/* ===== Converter ===== */
.input-row {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.input-row input[type="number"] {
  flex: 1;
  padding: 10px 12px;
  font-size: 1.1rem;
  border: 2px solid var(--border);
  border-radius: 6px;
  font-family: inherit;
  transition: border-color 0.15s;
}

.input-row input[type="number"]:focus {
  outline: none;
  border-color: var(--primary-light);
}

.input-row select {
  padding: 10px 10px;
  font-size: 1rem;
  border: 2px solid var(--border);
  border-radius: 6px;
  font-family: inherit;
  background: #fff;
  cursor: pointer;
  min-width: 80px;
  transition: border-color 0.15s;
}

.input-row select:focus {
  outline: none;
  border-color: var(--primary-light);
}

/* ===== Results Grid ===== */
.results-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 8px;
}

.result-item {
  padding: 10px 12px;
  border-radius: 6px;
  border: 1px solid var(--border);
}

.result-item.shaku {
  background: var(--shaku-bg);
  border-color: #b8d0e8;
}

.result-item.metric {
  background: var(--metric-bg);
  border-color: #e0c9b0;
}

.result-item.active-unit {
  border-color: var(--primary-light);
  outline: 2px solid var(--primary-light);
}

.result-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 2px;
}

.result-value {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
  word-break: break-all;
}

.result-hint {
  font-size: 0.72rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.legend {
  display: flex;
  gap: 12px;
  margin-top: 10px;
  font-size: 0.78rem;
  color: var(--text-muted);
}

.legend-dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  margin-right: 4px;
  vertical-align: middle;
}

/* ===== Reference Table ===== */
.table-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.ref-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  min-width: 400px;
}

.ref-table th,
.ref-table td {
  padding: 8px 10px;
  text-align: right;
  border: 1px solid var(--border);
  white-space: nowrap;
}

.ref-table th {
  background: var(--primary);
  color: #fff;
  font-weight: 600;
  text-align: center;
}

.ref-table th.shaku-header {
  background: var(--primary-light);
}

.ref-table th.metric-header {
  background: var(--accent);
}

.ref-table td:first-child {
  font-weight: 600;
  text-align: center;
  background: #f0f4f8;
}

.ref-table tr:nth-child(even) td {
  background: #fafaf8;
}

.ref-table tr:nth-child(even) td:first-child {
  background: #e8edf2;
}

.ref-table .divider th {
  background: #e8edf2;
  color: var(--text-muted);
  font-size: 0.78rem;
  padding: 4px;
}

/* ===== Tips ===== */
.tip-card {
  background: #fffbf5;
  border-color: #e8d5b8;
}

.tip-card h2 {
  color: var(--accent);
  border-bottom-color: #e8d5b8;
}

.tips {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.tips li {
  padding: 8px 10px;
  background: #fff;
  border-radius: 6px;
  border: 1px solid #e8d5b8;
  font-size: 0.9rem;
  line-height: 1.5;
}

.tips li strong {
  color: var(--primary);
}

.tips li span {
  color: var(--accent);
  font-weight: 600;
}

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 16px;
  font-size: 0.78rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
}

/* ===== Empty state ===== */
.empty-state {
  color: var(--text-muted);
  font-size: 0.9rem;
  text-align: center;
  padding: 16px 0;
  grid-column: 1 / -1;
}

/* ===== Print ===== */
@media print {
  header, .tabs, .converter, .tip-card, footer {
    display: none;
  }

  .tab-content {
    display: flex !important;
    break-inside: avoid;
  }

  .card {
    box-shadow: none;
    border: 1px solid #ccc;
    break-inside: avoid;
  }

  .ref-table {
    min-width: unset;
  }
}

/* ===== Responsive ===== */
@media (max-width: 480px) {
  header h1 {
    font-size: 1.25rem;
  }

  .results-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .input-row input[type="number"] {
    font-size: 1rem;
  }
}