/* ===== CSS Variables ===== */
:root {
  --bg-primary: #0f1219;
  --bg-secondary: #141820;
  --bg-card: #1a1f2b;
  --bg-card-hover: #1f2535;
  --blue: #3b82f6;
  --blue-dim: rgba(59, 130, 246, 0.12);
  --blue-glow: rgba(59, 130, 246, 0.3);
  --cyan: #06b6d4;
  --cyan-dim: rgba(6, 182, 212, 0.1);
  --text-primary: #e8eaf0;
  --text-secondary: #8892a4;
  --text-muted: #4f5a6e;
  --border-color: rgba(255, 255, 255, 0.06);
  --border-blue: rgba(59, 130, 246, 0.2);
  --font-display: 'Space Grotesk', sans-serif;
  --font-body: 'Noto Sans JP', sans-serif;
  --radius: 12px;
  --radius-lg: 16px;
}

/* ===== Reset & Base ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.8;
  -webkit-text-size-adjust: 100%;
  overflow-x: hidden;
}
a { color: var(--blue); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--cyan); text-decoration: none; }
img { max-width: 100%; }

/* ===== Scroll Reveal ===== */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Layout ===== */
.container { max-width: 880px; margin: 0 auto; padding: 0 24px; }

/* ===== Header ===== */
header {
  background: rgba(15, 18, 25, 0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  padding: 14px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}
header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
header a {
  color: var(--text-primary);
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: -0.3px;
}
header nav a {
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 400;
  color: var(--text-secondary);
  margin-left: 20px;
}
header nav a:hover { color: var(--blue); }

/* ===== Hero ===== */
.hero {
  background: linear-gradient(160deg, var(--bg-primary) 0%, #111827 40%, #0f1f3d 100%);
  padding: 56px 0 44px;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute;
  top: -120px;
  left: 50%;
  transform: translateX(-50%);
  width: 600px;
  height: 400px;
  background: radial-gradient(ellipse, var(--blue-dim) 0%, transparent 70%);
  pointer-events: none;
}
.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 4vw, 2.4rem);
  font-weight: 700;
  margin-bottom: 12px;
  letter-spacing: -0.5px;
  position: relative;
}
.hero p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  max-width: 540px;
  margin: 0 auto;
  line-height: 1.8;
  position: relative;
}

/* ===== Breadcrumb ===== */
.breadcrumb { font-size: .85rem; color: var(--text-muted); padding: 14px 0; }
.breadcrumb a { color: var(--blue); }

/* ===== Calculator Card ===== */
.calc-card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
  padding: 32px;
  margin: 24px 0;
}
.calc-card h2 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin-bottom: 18px;
  display: flex;
  align-items: center;
  gap: 8px;
}

/* ===== Form Elements ===== */
.form-group { margin-bottom: 18px; }
.form-group label {
  display: block;
  font-weight: 500;
  margin-bottom: 7px;
  font-size: 0.88rem;
  color: var(--text-secondary);
}
.form-group input, .form-group select {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  font-size: 0.95rem;
  transition: border-color .2s, box-shadow .2s;
  font-family: var(--font-body);
  background: var(--bg-secondary);
  color: var(--text-primary);
  -webkit-appearance: none;
  appearance: none;
  outline: none;
}
.form-group input:focus, .form-group select:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 3px var(--blue-dim);
}
.form-group input::placeholder { color: var(--text-muted); }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }

.btn {
  display: inline-block;
  background: var(--blue);
  color: #fff;
  padding: 12px 32px;
  border: none;
  border-radius: 10px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: box-shadow .2s, transform .2s;
  font-family: var(--font-body);
}
.btn:hover {
  box-shadow: 0 4px 20px var(--blue-glow);
  transform: translateY(-1px);
  text-decoration: none;
}
.btn:active { transform: translateY(0); }
.btn-block { display: block; width: 100%; text-align: center; }

/* ===== Result ===== */
.result-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-blue);
  border-radius: var(--radius);
  padding: 24px;
  margin-top: 20px;
  display: none;
}
.result-box.show { display: block; animation: fadeIn .4s ease; }
.result-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 4px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 500;
}
.result-value {
  font-family: var(--font-display);
  font-size: 1.8rem;
  font-weight: 700;
  letter-spacing: -0.5px;
}
.result-sub {
  font-size: 0.88rem;
  color: var(--text-secondary);
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--border-color);
}
@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }

/* ===== Section headings ===== */
.section-heading {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 600;
  margin: 24px 0 8px;
  padding-left: 12px;
  border-left: 3px solid var(--blue);
  letter-spacing: -0.3px;
}

/* ===== Content Sections ===== */
.content-section {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  padding: 28px;
  margin: 20px 0;
}
.content-section h2 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin-bottom: 14px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border-color);
}
.content-section h3 { font-size: 1rem; margin: 14px 0 8px; }
.content-section p { margin-bottom: 12px; color: var(--text-secondary); font-size: 0.9rem; }
.content-section ul, .content-section ol { margin: 8px 0 14px 22px; color: var(--text-secondary); }
.content-section li { margin-bottom: 6px; font-size: 0.9rem; }
.formula {
  background: var(--bg-secondary);
  border-left: 3px solid var(--blue);
  padding: 16px;
  border-radius: 0 10px 10px 0;
  font-family: 'Courier New', monospace;
  margin: 12px 0;
  font-size: 0.88rem;
  line-height: 1.8;
  color: var(--text-secondary);
}

/* ===== FAQ ===== */
.faq-item { border-bottom: 1px solid var(--border-color); padding: 16px 0; }
.faq-item:last-child { border-bottom: none; }
.faq-q { font-weight: 600; margin-bottom: 8px; }
.faq-q::before { content: 'Q. '; color: var(--blue); }
.faq-a { color: var(--text-secondary); padding-left: 22px; line-height: 1.8; font-size: 0.9rem; }
.faq-a::before { content: 'A. '; color: var(--blue); font-weight: 600; }

/* ===== Tool Grid (Index) ===== */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin: 12px 0 8px;
}
.tool-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--border-color);
  padding: 22px;
  transition: transform .25s, box-shadow .25s, border-color .25s;
  position: relative;
  overflow: hidden;
}
.tool-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--blue), var(--cyan));
  opacity: 0;
  transition: opacity 0.3s;
}
.tool-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 28px rgba(0,0,0,0.3);
  border-color: var(--border-blue);
}
.tool-card:hover::before { opacity: 1; }
.tool-card h3 {
  font-family: var(--font-display);
  font-size: 0.98rem;
  font-weight: 600;
  margin-bottom: 8px;
}
.tool-card h3 a { color: var(--text-primary); transition: color 0.2s; }
.tool-card h3 a:hover { color: var(--blue); }
.tool-card p {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-bottom: 12px;
  line-height: 1.65;
}
.tool-card .tag {
  display: inline-block;
  background: var(--blue-dim);
  color: var(--blue);
  font-size: 0.68rem;
  padding: 3px 10px;
  border-radius: 100px;
  font-weight: 600;
  letter-spacing: 0.2px;
}

/* ===== Internal Links ===== */
.internal-links {
  background: var(--bg-secondary);
  border-radius: var(--radius);
  padding: 20px;
  margin: 20px 0;
  border: 1px solid var(--border-color);
}
.internal-links h3 { font-size: 0.95rem; margin-bottom: 12px; }
.internal-links ul { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 8px; }
.internal-links li a {
  display: inline-block;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 6px 14px;
  border-radius: 100px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  transition: all .2s;
}
.internal-links li a:hover {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}

/* ===== Ad Placeholder ===== */
.ad-placeholder {
  background: var(--bg-secondary);
  border: 1px dashed var(--border-color);
  border-radius: 8px;
  padding: 36px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.8rem;
  margin: 20px 0;
  min-height: 90px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ===== Ad Unit ===== */
.ad-unit { margin: 20px 0; min-height: 90px; text-align: center; overflow: hidden; }
.ad-unit ins { display: block; }

/* ===== Footer ===== */
footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 32px 0;
  margin-top: 28px;
  text-align: center;
  font-size: 0.82rem;
}
footer a { color: var(--blue); }
footer a:hover { color: var(--cyan); }
footer .footer-links { margin-bottom: 10px; }
footer .footer-links a { margin: 0 10px; color: var(--text-secondary); }
footer p { color: var(--text-muted); }

/* ===== Utility ===== */
.mt-2 { margin-top: 16px; }
.mb-2 { margin-bottom: 16px; }
.text-center { text-align: center; }
.text-sm { font-size: .9rem; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero { padding: 40px 0 32px; }
  .hero h1 { font-size: 1.5rem; }
  .hero p { font-size: 0.88rem; padding: 0 8px; }
  .content-section { padding: 22px 18px; }
  .calc-card { padding: 22px 18px; }
  .tool-grid { grid-template-columns: 1fr; gap: 12px; }
  .form-row { grid-template-columns: 1fr; }
  header nav a { margin-left: 12px; font-size: 0.8rem; }
}

@media (max-width: 480px) {
  .form-group input, .form-group select { font-size: 16px; padding: 12px 12px; }
  .result-value { font-size: 1.4rem; }
  .btn { padding: 12px 20px; font-size: 0.92rem; }
  header .container { padding: 0 16px; }
  .internal-links ul { gap: 6px; }
  .internal-links li a { padding: 5px 10px; font-size: 0.75rem; }
}

@media (pointer: coarse) {
  .btn { min-height: 48px; }
  .form-group input, .form-group select { min-height: 48px; }
}