/* ToolsHub — Global Design System */
:root {
  --bg: #ffffff;
  --bg-secondary: #f7f8fa;
  --bg-tool: #f0f4f8;
  --text: #1a1a2e;
  --text-secondary: #5a5a7a;
  --text-muted: #8a8aa0;
  --brand: #2563eb;
  --brand-dark: #1d4ed8;
  --brand-light: #dbeafe;
  --accent: #f59e0b;
  --accent-dark: #d97706;
  --success: #10b981;
  --danger: #ef4444;
  --border: #e2e8f0;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-lg: 0 4px 12px rgba(0,0,0,0.1);
  --radius: 8px;
  --radius-lg: 12px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; height: auto; }
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── HEADER ── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  height: 48px;
  display: flex;
  align-items: center;
  padding: 0 16px;
}

.site-header .logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 6px;
}

.site-header .logo span { color: var(--brand); }

.site-header nav {
  margin-left: auto;
  display: flex;
  gap: 20px;
  font-size: 0.85rem;
}

.site-header nav a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.2s;
}
.site-header nav a:hover { color: var(--brand); }

/* ── BREADCRUMB ── */
.breadcrumb {
  font-size: 0.8rem;
  color: var(--text-muted);
  padding: 12px 0 0;
}
.breadcrumb a { color: var(--text-secondary); }
.breadcrumb a:hover { color: var(--brand); }

/* ── CONTAINER ── */
.container {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 16px;
}

/* ── TOOL CARD ── */
.tool-box {
  background: var(--bg-tool);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  margin: 20px 0;
}

/* ── FORM ELEMENTS ── */
.form-group {
  margin-bottom: 16px;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.form-group input,
.form-group select {
  width: 100%;
  height: 44px;
  padding: 0 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 1rem;
  color: var(--text);
  background: var(--bg);
  transition: border-color 0.2s;
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--brand);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.input-prefix {
  position: relative;
}
.input-prefix::before {
  content: '\20B9';
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  font-weight: 600;
}
.input-prefix input {
  padding-left: 28px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

/* ── RANGE SLIDER ── */
.range-group input[type="range"] {
  width: 100%;
  height: 6px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--border);
  border-radius: 3px;
  outline: none;
  margin-top: 8px;
}
.range-group input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  background: var(--brand);
  border-radius: 50%;
  cursor: pointer;
}

/* ── BUTTON ── */
.btn-calculate {
  width: 100%;
  height: 48px;
  background: var(--brand);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
  margin-top: 8px;
}
.btn-calculate:hover { background: var(--brand-dark); }

/* ── RESULTS ── */
.result-box {
  text-align: center;
  padding: 24px;
  margin-top: 20px;
  background: var(--bg);
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.result-main {
  font-size: 2rem;
  font-weight: 700;
  color: var(--brand);
  line-height: 1.2;
}

.result-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.result-item {
  padding: 12px;
  background: var(--bg-secondary);
  border-radius: var(--radius);
  text-align: center;
}

.result-item .val {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
}

.result-item .lbl {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.result-item.positive .val { color: var(--success); }
.result-item.negative .val { color: var(--danger); }

/* ── CONTENT SECTIONS ── */
.content-section {
  margin: 32px 0;
}

.content-section h2 {
  font-size: 1.35rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text);
}

.content-section h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 16px 0 8px;
}

.content-section p {
  margin-bottom: 12px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.content-section ul, .content-section ol {
  padding-left: 20px;
  margin-bottom: 12px;
  color: var(--text-secondary);
}

.content-section li { margin-bottom: 6px; }

/* ── FAQ ── */
.faq-item {
  border-bottom: 1px solid var(--border);
  padding: 16px 0;
}

.faq-item summary {
  font-weight: 600;
  cursor: pointer;
  color: var(--text);
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.faq-item summary::after {
  content: '+';
  font-size: 1.2rem;
  color: var(--brand);
  transition: transform 0.2s;
}

.faq-item[open] summary::after {
  content: '\2212';
}

.faq-item .faq-answer {
  padding-top: 8px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ── RELATED TOOLS ── */
.related-tools {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.related-tool-card {
  display: block;
  padding: 16px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--text);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.related-tool-card:hover {
  border-color: var(--brand);
  box-shadow: var(--shadow);
  text-decoration: none;
}

.related-tool-card .rtc-title {
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 4px;
}

.related-tool-card .rtc-desc {
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* ── FOOTER ── */
.site-footer {
  margin-top: 48px;
  padding: 24px 16px;
  border-top: 1px solid var(--border);
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.site-footer a { color: var(--text-secondary); }
.site-footer .footer-links { margin-bottom: 8px; }
.site-footer .footer-links a { margin: 0 8px; }

/* ── FORMULA TABLE ── */
.formula-table {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: 0.9rem;
}

.formula-table th, .formula-table td {
  padding: 10px 12px;
  border: 1px solid var(--border);
  text-align: left;
}

.formula-table th {
  background: var(--bg-secondary);
  font-weight: 600;
  color: var(--text);
}

.formula-table td { color: var(--text-secondary); }

/* ── LAST UPDATED ── */
.last-updated {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 4px;
}

/* ── HOMEPAGE ── */
.hero {
  text-align: center;
  padding: 48px 16px 32px;
}

.hero h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.hero p {
  color: var(--text-secondary);
  max-width: 480px;
  margin: 0 auto;
}

.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
  padding: 0 16px;
  max-width: 960px;
  margin: 0 auto;
}

.tool-card {
  display: block;
  padding: 20px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  text-decoration: none;
  color: var(--text);
  transition: border-color 0.2s, box-shadow 0.2s, transform 0.2s;
}

.tool-card:hover {
  border-color: var(--brand);
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
  text-decoration: none;
}

.tool-card .tc-icon { font-size: 1.5rem; margin-bottom: 8px; }
.tool-card .tc-title { font-weight: 600; font-size: 0.95rem; margin-bottom: 4px; }
.tool-card .tc-desc { font-size: 0.8rem; color: var(--text-muted); }

/* ── RESPONSIVE ── */
@media (min-width: 768px) {
  .container { padding: 0 24px; }
  .tool-box { padding: 32px; }
  .hero { padding: 64px 24px 40px; }
  .hero h1 { font-size: 2.2rem; }
}

@media (min-width: 1024px) {
  .container { padding: 0 32px; }
}

@media (max-width: 480px) {
  .form-row { grid-template-columns: 1fr; }
  .result-main { font-size: 1.6rem; }
}