:root {
  --bg: #f6f7f9;
  --card: #ffffff;
  --ink: #1f2430;
  --muted: #5b6472;
  --accent: #2456d6;
  --border: #e2e6ee;
}

* { box-sizing: border-box; }

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

.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px 22px;
  background: var(--card);
  border-bottom: 1px solid var(--border);
}

.brand {
  font-size: 20px;
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
}

.site-header nav a {
  margin-left: 16px;
  color: var(--muted);
  text-decoration: none;
}

.site-header nav a:hover { color: var(--accent); }

main {
  max-width: 940px;
  margin: 0 auto;
  padding: 28px 20px 48px;
}

.hero h1 {
  font-size: clamp(26px, 4vw, 38px);
  line-height: 1.2;
  margin-bottom: 10px;
}

.hero p {
  color: var(--muted);
  font-size: 17px;
  max-width: 720px;
}

.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin: 28px 0;
}

.tool-card {
  display: block;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px;
  text-decoration: none;
  color: var(--ink);
  transition: box-shadow 0.15s ease, transform 0.15s ease;
}

.tool-card:hover {
  box-shadow: 0 6px 18px rgba(31, 36, 48, 0.08);
  transform: translateY(-2px);
}

.tool-card h2 {
  margin: 0 0 8px;
  font-size: 18px;
  color: var(--accent);
}

.tool-card p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.note {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

section { margin-bottom: 28px; }

h1 { font-size: 30px; line-height: 1.25; }
h2 { font-size: 20px; margin-top: 26px; }

.tool-body {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

.tool-body label {
  display: block;
  font-weight: 600;
  margin: 14px 0 5px;
  font-size: 14px;
}

.tool-body input[type="number"],
.tool-body input[type="text"],
.tool-body select {
  width: 100%;
  max-width: 360px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 15px;
  background: #fff;
}

.btn-row { margin: 18px 0 8px; }

button {
  background: var(--accent);
  color: #fff;
  border: 0;
  border-radius: 8px;
  padding: 11px 18px;
  font-size: 15px;
  cursor: pointer;
  margin-right: 8px;
}

button.secondary {
  background: #eef1f7;
  color: var(--ink);
}

button:hover { filter: brightness(1.05); }

.result {
  background: #f0f5ff;
  border: 1px solid #d5e2ff;
  border-radius: 10px;
  padding: 16px;
  margin-top: 16px;
  min-height: 30px;
}

.result strong { font-size: 22px; color: var(--accent); }

.result p { margin: 6px 0; }

table {
  width: 100%;
  border-collapse: collapse;
  background: var(--card);
  margin: 16px 0;
  font-size: 14px;
}

th, td {
  text-align: left;
  padding: 9px 11px;
  border-bottom: 1px solid var(--border);
}

th { background: #f0f2f7; }

.small { color: var(--muted); font-size: 13px; }

.faq { border-top: 1px solid var(--border); margin-top: 22px; }

.faq details {
  border-bottom: 1px solid var(--border);
  padding: 12px 2px;
}

.faq summary {
  font-weight: 600;
  cursor: pointer;
}

.site-footer {
  border-top: 1px solid var(--border);
  background: var(--card);
  padding: 18px 22px;
  text-align: center;
  color: var(--muted);
  font-size: 14px;
}

@media (max-width: 600px) {
  .site-header { flex-wrap: wrap; gap: 8px; }
}