:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --ink: #111827;
  --muted: #6b7280;
  --bg: #f9fafb;
  --card: #ffffff;
  --border: #e5e7eb;
  --radius: 12px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
}

.container { max-width: 860px; margin: 0 auto; padding: 0 20px; }

/* header */
.site-header {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}
.header-inner { display: flex; align-items: center; justify-content: space-between; min-height: 60px; flex-wrap: wrap; gap: 8px; }
.logo { font-weight: 700; font-size: 1.15rem; color: var(--ink); text-decoration: none; }
.logo:hover { color: var(--primary); }
.nav { display: flex; gap: 18px; flex-wrap: wrap; }
.nav a { color: var(--muted); text-decoration: none; font-size: 0.95rem; }
.nav a:hover { color: var(--primary); }

/* typography */
h1 { font-size: 1.9rem; line-height: 1.25; margin: 28px 0 10px; }
.tagline { color: var(--muted); font-size: 1.05rem; margin: 0 0 22px; }
.prose h2 { font-size: 1.3rem; margin: 32px 0 12px; }

/* breadcrumb */
.breadcrumb { font-size: 0.85rem; color: var(--muted); margin: 20px 0 0; }
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--primary); }

/* cards (home) */
.card-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; margin: 26px 0; }
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  text-decoration: none;
  color: var(--ink);
  transition: transform 0.12s ease, box-shadow 0.12s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 6px 18px rgba(0, 0, 0, 0.08); }
.card h2 { margin: 0 0 8px; font-size: 1.15rem; color: var(--primary); }
.card p { margin: 0; color: var(--muted); font-size: 0.92rem; }

/* tool box */
.tool-box {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin: 18px 0 0;
}
.modes { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 18px; }
.mode-btn {
  font-size: 0.95rem;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--ink);
  cursor: pointer;
  min-height: 44px;
}
.mode-btn.active { background: var(--primary); border-color: var(--primary); color: #fff; }

.fields { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 14px; margin-bottom: 16px; }
.field label { display: block; font-size: 0.9rem; font-weight: 600; margin-bottom: 6px; }
.field input {
  width: 100%;
  font-size: 1.05rem;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  min-height: 48px;
  color: var(--ink);
}
.field input:focus { outline: 2px solid var(--primary); outline-offset: 1px; border-color: transparent; }
.hint { font-size: 0.82rem; color: var(--muted); margin: 6px 0 0; }

.btn {
  font-size: 1.05rem;
  font-weight: 600;
  padding: 13px 26px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  min-height: 48px;
  text-decoration: none;
  display: inline-block;
}
.btn:hover { background: var(--primary-dark); }

.result {
  margin-top: 18px;
  padding: 16px;
  background: #eff6ff;
  border-left: 4px solid var(--primary);
  border-radius: 8px;
}
.result-line { font-size: 1.15rem; margin: 0; }
.result-line strong { color: var(--primary-dark); }
.result-sub { margin: 4px 0 0; color: var(--muted); }
.hidden { display: none; }

/* ad slot */
.ad-slot { min-height: 90px; margin: 20px 0; background: transparent; }

/* faq */
details {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 16px;
  margin: 8px 0;
}
summary { cursor: pointer; font-weight: 600; }
details p { margin: 10px 0 0; color: #374151; }

/* related */
.related a { color: var(--primary); }

/* footer */
.site-footer {
  margin-top: 48px;
  padding: 26px 0;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.9rem;
}
.footer-links a { color: var(--muted); margin: 0 4px; }
.footer-links a:hover { color: var(--primary); }

@media (max-width: 560px) {
  h1 { font-size: 1.55rem; }
  .header-inner { flex-direction: column; align-items: flex-start; padding: 10px 0; }
}