:root {
  --bg-color: #0b0f19;
  --bg-card: #131b2e;
  --bg-card-hover: #19243d;
  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  --border-color: #24324f;
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --accent-cyan: #06b6d4;
  --accent-green: #10b981;
  --accent-amber: #f59e0b;
  --accent-purple: #8b5cf6;
  --card-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg-color: #f8fafc;
    --bg-card: #ffffff;
    --bg-card-hover: #f1f5f9;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --card-shadow: 0 4px 20px -4px rgba(0, 0, 0, 0.08);
  }
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container {
  max-width: 1040px;
  margin: 0 auto;
  padding: 0 1.25rem;
  width: 100%;
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--border-color);
  background: var(--bg-card);
  padding: 0.85rem 1.25rem;
}

.header-content {
  max-width: 1040px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand-link {
  text-decoration: none;
}

.brand-badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  transition: color 0.2s;
}

.brand-badge:hover {
  color: var(--primary);
}

.header-badges {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.source-tag {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent-cyan);
  background: rgba(6, 182, 212, 0.12);
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  border: 1px solid rgba(6, 182, 212, 0.3);
}

.year-badge {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent-green);
  background: rgba(16, 185, 129, 0.12);
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  border: 1px solid rgba(16, 185, 129, 0.3);
}

/* Hero */
.hero-section {
  text-align: center;
  padding: 3rem 0 2rem;
}

.hero-title {
  font-size: clamp(1.8rem, 4vw, 2.75rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 1rem;
}

.hero-title span {
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent-cyan) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-description {
  color: var(--text-muted);
  font-size: 1.1rem;
  max-width: 680px;
  margin: 0 auto 1.5rem;
}

/* Index Switcher Tabs */
.index-tabs {
  display: inline-flex;
  background: var(--bg-card);
  padding: 0.35rem;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  margin-bottom: 2rem;
  gap: 0.35rem;
}

.tab-btn {
  background: none;
  border: none;
  padding: 0.6rem 1.4rem;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: 8px;
  transition: all 0.2s ease;
}

.tab-btn.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.35);
}

/* Main Calculator Grid */
.calc-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.75rem;
  margin-bottom: 3rem;
}

@media (min-width: 900px) {
  .calc-grid {
    grid-template-columns: 1.1fr 1fr;
    align-items: start;
  }
}

.calc-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 1.75rem;
  box-shadow: var(--card-shadow);
}

.card-header-badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent-cyan);
  margin-bottom: 0.5rem;
}

.card-title {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 1.25rem;
}

/* Form Groups */
.form-group {
  margin-bottom: 1.25rem;
}

.form-label {
  display: block;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 0.45rem;
}

.input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.input-prefix {
  position: absolute;
  left: 1rem;
  font-weight: 700;
  color: var(--text-muted);
  font-size: 1.1rem;
}

.calc-input {
  width: 100%;
  padding: 0.75rem 1rem;
  font-size: 1.05rem;
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  color: var(--text-main);
  font-family: var(--font-mono);
  outline: none;
  transition: border-color 0.2s;
}

.calc-input.with-prefix {
  padding-left: 2.2rem;
}

.calc-input:focus {
  border-color: var(--primary);
}

/* Quick Period Buttons */
.quick-presets {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
  margin-top: 0.5rem;
}

.preset-btn {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.45rem 0.25rem;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s;
  text-align: center;
}

.preset-btn:hover, .preset-btn.active {
  background: rgba(59, 130, 246, 0.15);
  border-color: var(--primary);
  color: var(--primary);
}

/* Date Info Hint */
.date-hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.35rem;
}

/* Results Panel */
.results-card {
  background: linear-gradient(145deg, var(--bg-card) 0%, rgba(30, 41, 59, 0.6) 100%);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 1.75rem;
  box-shadow: var(--card-shadow);
  position: relative;
  overflow: hidden;
}

.results-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--primary), var(--accent-cyan));
}

.result-hero {
  margin-bottom: 1.5rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-color);
}

.result-label {
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.25rem;
}

.result-value {
  font-family: var(--font-mono);
  font-size: clamp(2rem, 5vw, 2.75rem);
  font-weight: 800;
  color: var(--accent-green);
  line-height: 1.1;
  font-variant-numeric: tabular-nums;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.stat-box {
  background: var(--bg-color);
  padding: 0.85rem 1rem;
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.stat-title {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 0.2rem;
}

.stat-num {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  font-variant-numeric: tabular-nums;
}

.stat-num.highlight {
  color: var(--accent-cyan);
}

/* Breakdown Formula Box */
.breakdown-box {
  background: var(--bg-color);
  border: 1px dashed var(--border-color);
  border-radius: 10px;
  padding: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.breakdown-title {
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.4rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.formula-code {
  font-family: var(--font-mono);
  background: rgba(0, 0, 0, 0.3);
  padding: 0.4rem 0.6rem;
  border-radius: 6px;
  margin: 0.4rem 0;
  color: var(--accent-amber);
  word-break: break-all;
}

/* Actions Buttons */
.action-buttons {
  display: flex;
  gap: 0.75rem;
}

.action-btn {
  flex: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: 10px;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all 0.2s ease;
  text-decoration: none;
}

.btn-whatsapp {
  background: #25D366;
  color: #0b0f19;
}

.btn-whatsapp:hover {
  background: #20bd5a;
}

.btn-copy {
  background: var(--bg-color);
  border-color: var(--border-color);
  color: var(--text-main);
}

.btn-copy:hover {
  border-color: var(--primary);
  color: var(--primary);
}

/* Reference Benchmark Table */
.benchmark-section {
  margin-bottom: 3rem;
}

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.table-wrapper {
  overflow-x: auto;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 14px;
}

.benchmark-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  text-align: left;
}

.benchmark-table th, .benchmark-table td {
  padding: 0.85rem 1.25rem;
  border-bottom: 1px solid var(--border-color);
}

.benchmark-table th {
  background: rgba(0, 0, 0, 0.2);
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
}

.benchmark-table tr:last-child td {
  border-bottom: none;
}

.val-pct {
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--accent-cyan);
}

/* FAQ */
.faq-section {
  margin-bottom: 3rem;
}

.faq-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 768px) {
  .faq-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.faq-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 1.25rem;
}

.faq-card h3 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.faq-card p {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.5;
}

/* Cross Promo */
.cross-promo-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 2rem;
  text-align: center;
  margin-bottom: 3rem;
}

.cross-promo-badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--primary);
  background: rgba(59, 130, 246, 0.1);
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  margin-bottom: 0.75rem;
}

.cross-promo-card h3 {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.cross-promo-card p {
  color: var(--text-muted);
  margin-bottom: 1.25rem;
  font-size: 0.95rem;
}

.promo-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.6rem;
}

.promo-pill {
  display: inline-flex;
  align-items: center;
  padding: 0.45rem 0.9rem;
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: 999px;
  color: var(--text-main);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
  transition: all 0.2s ease;
}

.promo-pill:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-1px);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border-color);
  background: var(--bg-card);
  padding: 1.5rem 0;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: auto;
}

.site-footer a {
  color: var(--primary);
  text-decoration: none;
}