:root {
  --primary: #004581;
  --primary-dark: #003463;
  --primary-light: #e8f0f7;
  --accent: #1a6bb8;
  --text: #1f2937;
  --text-muted: #6b7280;
  --bg: #f5f7fa;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --pill-bg: #dbe6f0;
  --pill-text: #004581;
  --success: #16a34a;
  --danger: #dc2626;
  --radius: 10px;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

.container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 24px;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Header */
.site-header {
  background: var(--primary);
  color: #fff;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: #fff;
  font-weight: 700;
  font-size: 1.15rem;
}
.brand:hover { text-decoration: none; opacity: 0.9; }
.brand-icon {
  background: rgba(255,255,255,0.15);
  width: 34px;
  height: 34px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
}
.main-nav {
  display: flex;
  gap: 28px;
}
.main-nav a {
  color: #e5edf5;
  font-weight: 500;
  font-size: 0.95rem;
  padding: 6px 0;
  border-bottom: 2px solid transparent;
}
.main-nav a:hover, .main-nav a.active {
  color: #fff;
  text-decoration: none;
  border-bottom-color: #fff;
}
.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: #fff;
  font-size: 1.4rem;
  cursor: pointer;
}

@media (max-width: 720px) {
  .main-nav {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--primary-dark);
    flex-direction: column;
    padding: 12px 24px;
    gap: 4px;
    z-index: 50;
  }
  .main-nav.open { display: flex; }
  .main-nav a { padding: 10px 0; border-bottom: 1px solid rgba(255,255,255,0.1); }
  .nav-toggle { display: block; }
  .site-header { position: relative; }
}

/* Hero */
.hero {
  padding: 64px 0 40px;
}
.hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin: 0 0 16px;
  line-height: 1.15;
  color: #0f172a;
}
.hero h1 .accent { color: var(--primary); }
.hero p.lead {
  color: var(--text-muted);
  font-size: 1.1rem;
  max-width: 640px;
  margin: 0;
}

/* Category cards */
.category-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  padding: 24px 0 64px;
}
@media (max-width: 900px) {
  .category-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 640px) {
  .category-grid { grid-template-columns: 1fr; }
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
}
.card-icon {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  background: var(--primary);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 16px;
}
.card h3 {
  margin: 0 0 10px;
  font-size: 1.25rem;
}
.card p {
  color: var(--text-muted);
  font-size: 0.94rem;
  margin: 0 0 18px;
  flex-grow: 0;
}
.pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}
.pill {
  background: var(--pill-bg);
  color: var(--pill-text);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 5px 12px;
  border-radius: 999px;
}
.open-link {
  margin-top: auto;
  font-weight: 700;
  color: var(--primary);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 28px 0 40px;
  margin-top: 40px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
}
.site-footer p { margin: 4px 0; }
.site-footer a { color: var(--primary); font-weight: 600; }

/* ==== Tool pages ==== */
.tool-header {
  padding: 40px 0 12px;
}
.tool-header h1 {
  font-size: 1.9rem;
  margin: 0 0 8px;
  color: #0f172a;
}
.tool-header p {
  color: var(--text-muted);
  margin: 0;
}
.breadcrumb {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}
.breadcrumb a { color: var(--text-muted); }

.tab-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 24px 0;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0;
}
.tab-btn {
  background: none;
  border: none;
  padding: 10px 16px;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  border-bottom: 3px solid transparent;
  border-radius: 6px 6px 0 0;
}
.tab-btn:hover { background: var(--primary-light); color: var(--primary); }
.tab-btn.active { color: var(--primary); border-bottom-color: var(--primary); }

.tab-panel { display: none; padding: 24px 0 60px; }
.tab-panel.active { display: block; }

.tool-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}
@media (max-width: 800px) {
  .tool-grid { grid-template-columns: 1fr; }
}

.panel-box {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}
.panel-box h4 {
  margin: 0 0 12px;
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.02em;
  color: var(--text-muted);
}

textarea, input[type=text], input[type=number], select {
  width: 100%;
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  font-size: 0.92rem;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fbfcfe;
  color: var(--text);
  resize: vertical;
}
textarea { min-height: 220px; }
input[type=text], input[type=number], select {
  font-family: inherit;
}
select { cursor: pointer; }
label { font-weight: 600; font-size: 0.88rem; display: block; margin-bottom: 6px; }

.field { margin-bottom: 14px; }
.row { display: flex; gap: 12px; flex-wrap: wrap; }
.row > * { flex: 1; min-width: 140px; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--primary);
  color: #fff;
  border: none;
  padding: 10px 18px;
  font-size: 0.92rem;
  font-weight: 600;
  border-radius: 8px;
  cursor: pointer;
  margin: 4px 6px 4px 0;
}
.btn:hover { background: var(--primary-dark); text-decoration: none; }
.btn.secondary {
  background: #fff;
  color: var(--primary);
  border: 1px solid var(--primary);
}
.btn.secondary:hover { background: var(--primary-light); }
.btn.ghost {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
}
.btn.ghost:hover { background: var(--bg); }

.btn-row { margin: 14px 0; }

.status {
  margin-top: 12px;
  padding: 10px 14px;
  border-radius: 8px;
  font-size: 0.88rem;
  font-weight: 600;
  display: none;
}
.status.show { display: block; }
.status.ok { background: #ecfdf3; color: var(--success); border: 1px solid #bbf7d0; }
.status.err { background: #fef2f2; color: var(--danger); border: 1px solid #fecaca; }

.checkbox-row { display: flex; align-items: center; gap: 8px; margin-bottom: 10px; }
.checkbox-row input { width: auto; }
.checkbox-row label { margin: 0; font-weight: 500; }

.result-box {
  white-space: pre-wrap;
  word-break: break-word;
  font-family: 'SFMono-Regular', Consolas, monospace;
  font-size: 0.88rem;
  background: #fbfcfe;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  min-height: 60px;
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
  gap: 10px;
  margin-top: 14px;
}
.stat-card {
  background: var(--primary-light);
  border-radius: 8px;
  padding: 12px;
  text-align: center;
}
.stat-card .num { font-size: 1.4rem; font-weight: 800; color: var(--primary); }
.stat-card .label { font-size: 0.75rem; color: var(--text-muted); text-transform: uppercase; }

.tree-view { font-family: monospace; font-size: 0.85rem; }
.tree-view ul { list-style: none; margin: 0; padding-left: 18px; border-left: 1px dashed var(--border); }
.tree-view li { margin: 3px 0; }
.tree-key { color: var(--primary); font-weight: 700; }
.tree-type { color: var(--text-muted); font-size: 0.75rem; }
.tree-val { color: #b45309; }
.tree-toggle { cursor: pointer; user-select: none; color: var(--text-muted); margin-right: 4px; }

.diff-add { background: #dcfce7; color: #166534; }
.diff-del { background: #fee2e2; color: #991b1b; text-decoration: line-through; }
.diff-same { color: var(--text); }
.diff-line { display: block; padding: 1px 4px; font-family: monospace; font-size: 0.85rem; white-space: pre-wrap; }

.hint { font-size: 0.8rem; color: var(--text-muted); margin-top: 6px; }

.calc-result {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--primary);
  margin-top: 10px;
}

table.simple { width: 100%; border-collapse: collapse; font-size: 0.88rem; }
table.simple th, table.simple td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
table.simple th { color: var(--text-muted); font-size: 0.78rem; text-transform: uppercase; }

/* ==== Number Converter (single-panel, all-results-at-once) ==== */
.nc-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px;
  box-shadow: 0 8px 30px rgba(0, 69, 129, 0.10);
}
.nc-input-section {
  display: grid;
  grid-template-columns: 1fr 230px;
  gap: 20px;
  align-items: end;
}
.nc-actions {
  display: flex;
  gap: 10px;
  margin-top: 18px;
  flex-wrap: wrap;
}
.nc-results { margin-top: 28px; }
.nc-results-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 15px;
}
.nc-results-header h3 {
  color: var(--primary);
  font-size: 1.25rem;
  margin: 0;
}
.nc-result-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}
.nc-result-box {
  border: 1px solid var(--border);
  border-radius: 11px;
  overflow: hidden;
  background: #fff;
}
.nc-result-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 13px;
  background: #f7f9fb;
  border-bottom: 1px solid var(--border);
}
.nc-result-title span {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--primary);
}
.nc-copy-btn {
  padding: 5px 9px;
  font-size: 0.75rem;
  background: #fff;
  color: var(--primary);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
}
.nc-copy-btn:hover { border-color: var(--primary); background: var(--primary-light); }
.nc-result-value {
  padding: 14px;
  min-height: 70px;
  max-height: 180px;
  overflow: auto;
  word-break: break-word;
  white-space: pre-wrap;
  font-family: 'SFMono-Regular', Consolas, monospace;
  font-size: 0.82rem;
  color: #263746;
}
.nc-result-value.nc-empty { color: #9aa6b2; }
.nc-info {
  margin-top: 24px;
  padding: 16px;
  background: var(--primary-light);
  border-left: 4px solid var(--primary);
  border-radius: 8px;
  color: #36536a;
  font-size: 0.83rem;
}
@media (max-width: 750px) {
  .nc-card { padding: 18px; }
  .nc-input-section { grid-template-columns: 1fr; }
  .nc-result-grid { grid-template-columns: 1fr; }
}