/* ============================================
   Compound Interest Calculators — Shared Styles
   ============================================ */

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #dbeafe;
  --success: #16a34a;
  --success-light: #dcfce7;
  --warning: #ea580c;
  --bg: #f8fafc;
  --card: #ffffff;
  --text: #1e293b;
  --text-muted: #64748b;
  --border: #e2e8f0;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --shadow-lg: 0 10px 25px rgba(0,0,0,.08);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

/* Navigation */
.nav {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav-inner {
  max-width: 1120px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}
.nav-logo {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
}
.nav-links { display: flex; gap: 20px; list-style: none; }
.nav-links a {
  text-decoration: none;
  color: var(--text-muted);
  font-size: .9rem;
  font-weight: 500;
  transition: color .15s;
}
.nav-links a:hover { color: var(--primary); }

/* Layout */
.container { max-width: 1120px; margin: 0 auto; padding: 32px 24px; }

/* Hero */
.hero { text-align: center; padding: 56px 0 40px; }
.hero h1 { font-size: 2.2rem; font-weight: 800; letter-spacing: -.02em; margin-bottom: 12px; }
.hero p { color: var(--text-muted); font-size: 1.1rem; max-width: 560px; margin: 0 auto; }

/* Tool Cards */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
  margin-top: 32px;
}
.tool-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
  transition: box-shadow .2s, transform .2s;
  text-decoration: none;
  color: inherit;
  display: block;
}
.tool-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}
.tool-card h3 { font-size: 1.2rem; margin-bottom: 8px; color: var(--primary); }
.tool-card p { color: var(--text-muted); font-size: .93rem; }
.tool-card .badge {
  display: inline-block;
  background: var(--success-light);
  color: var(--success);
  font-size: .75rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 20px;
  margin-top: 12px;
}
.tool-card.coming-soon {
  opacity: .6;
  pointer-events: none;
}
.tool-card.coming-soon .badge {
  background: #fef3c7;
  color: #b45309;
}

/* Calculator Pages */
.calc-form {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: var(--shadow);
  margin-bottom: 28px;
}
.calc-form h2 { font-size: 1.3rem; margin-bottom: 24px; }

.form-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin-bottom: 20px;
}
.form-group { display: flex; flex-direction: column; }
.form-group label {
  font-size: .85rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.form-group input, .form-group select {
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  transition: border-color .15s;
  background: var(--bg);
}
.form-group input:focus, .form-group select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}
.form-group .hint {
  font-size: .78rem;
  color: var(--text-muted);
  margin-top: 4px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background .15s, transform .1s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn:active { transform: scale(.98); }

/* Results */
.results {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: var(--shadow);
}
.results h2 { font-size: 1.3rem; margin-bottom: 20px; }
.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 16px;
  margin-bottom: 28px;
}
.result-item {
  background: var(--primary-light);
  border-radius: 10px;
  padding: 20px;
  text-align: center;
}
.result-item .label {
  font-size: .78rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: .04em;
  margin-bottom: 4px;
}
.result-item .value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-dark);
}

/* Table */
table {
  width: 100%;
  border-collapse: collapse;
  font-size: .9rem;
}
th, td {
  padding: 10px 14px;
  text-align: right;
  border-bottom: 1px solid var(--border);
}
th {
  background: var(--bg);
  font-weight: 600;
  color: var(--text-muted);
  font-size: .8rem;
  text-transform: uppercase;
}
tr:hover td { background: #f1f5f9; }
.table-wrap { overflow-x: auto; }

/* Algorithm info box */
.algo-info {
  margin-top: 28px;
  padding: 20px;
  background: #fffbeb;
  border: 1px solid #fde68a;
  border-radius: var(--radius);
  font-size: .88rem;
}
.algo-info h4 { font-size: .95rem; margin-bottom: 6px; color: var(--warning); }
.algo-info .time { font-weight: 600; color: var(--text); }
.algo-info .comparison { color: var(--text-muted); font-size: .83rem; margin-top: 4px; }

/* Tabs */
.tab-nav { display: flex; gap: 0; margin-bottom: 28px; border-bottom: 2px solid var(--border); }
.tab-nav button {
  padding: 12px 24px;
  background: none;
  border: none;
  font-size: .95rem;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: color .15s, border-color .15s;
}
.tab-nav button.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
  font-weight: 600;
}
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* Footer */
.footer {
  text-align: center;
  padding: 32px 24px;
  color: var(--text-muted);
  font-size: .85rem;
  border-top: 1px solid var(--border);
  margin-top: 56px;
}
.footer a { color: var(--primary); text-decoration: none; }

/* About page */
.about-section { max-width: 720px; margin: 0 auto; }
.about-section h2 { font-size: 1.3rem; margin: 28px 0 12px; }
.about-section p { color: var(--text-muted); margin-bottom: 12px; }

/* Responsive */
@media (max-width: 640px) {
  .hero h1 { font-size: 1.6rem; }
  .tool-grid { grid-template-columns: 1fr; }
  .form-row { grid-template-columns: 1fr; }
  .nav-links { gap: 12px; }
  .nav-links a { font-size: .82rem; }
}

/* Utility */
.text-center { text-align: center; }
.mt-20 { margin-top: 20px; }
.hidden { display: none; }

/* Info icon + tooltip */
.formula-info-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  border: 1px solid var(--text-muted);
  background: none;
  color: var(--text-muted);
  font-size: .65rem;
  font-weight: 700;
  cursor: pointer;
  margin-left: 4px;
  vertical-align: middle;
  transition: all .15s;
  line-height: 1;
}
.formula-info-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-light);
}
.formula-tooltip {
  display: none;
  background: #1e293b;
  color: #e2e8f0;
  padding: 14px 18px;
  border-radius: 8px;
  font-size: .82rem;
  line-height: 1.7;
  margin-top: 10px;
  max-width: 600px;
}
.formula-tooltip.show {
  display: block;
}
.formula-tooltip .param-line {
  color: #94a3b8;
  font-size: .78rem;
  margin-bottom: 6px;
}
.formula-tooltip .formula-line {
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: .8rem;
}

/* Function annotation label */
.fn-label {
  font-size: .7rem;
  color: var(--text-muted);
  margin-top: 6px;
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  opacity: .7;
}

/* Language select dropdown */
.lang-select {
  background: none;
  border: 1px solid var(--border);
  padding: 4px 8px;
  border-radius: 6px;
  font-size: .82rem;
  color: var(--text);
  cursor: pointer;
  outline: none;
}
.lang-select:focus { border-color: var(--primary); }

/* Tools dropdown menu */
.nav-dropdown {
  position: relative;
  display: inline-block;
}
.nav-dropdown > a {
  cursor: pointer;
}
.nav-dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  min-width: 240px;
  z-index: 200;
  padding: 8px 0;
}
.nav-dropdown:hover .nav-dropdown-menu {
  display: block;
}
.nav-dropdown-menu a {
  display: block;
  padding: 8px 16px;
  text-decoration: none;
  color: var(--text);
  font-size: .88rem;
}
.nav-dropdown-menu a:hover {
  background: var(--primary-light);
  color: var(--primary);
}
.nav-dropdown-menu a.disabled {
  color: var(--text-muted);
  pointer-events: none;
  opacity: .5;
}

/* nav alignment */
.nav-links { align-items: center; }