:root {
  --bg: #f7f8fa;
  --card: #ffffff;
  --text: #1a202c;
  --muted: #64748b;
  --accent: #0f766e;
  --accent-dark: #115e59;
  --border: #e2e8f0;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(16, 24, 40, 0.08), 0 1px 2px rgba(16, 24, 40, 0.04);
}

* { box-sizing: border-box; }

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

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 960px; margin: 0 auto; padding: 0 20px; }

header {
  background: var(--card);
  border-bottom: 1px solid var(--border);
}

header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
}
.logo:hover { text-decoration: none; }
.logo span { color: var(--accent); }

nav a {
  margin-left: 18px;
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--muted);
}
nav a:hover { color: var(--text); }

main { padding: 40px 0 60px; }

.hero { text-align: center; padding: 20px 0 32px; }
.hero h1 { font-size: 2rem; margin: 0 0 12px; letter-spacing: -0.02em; }
.hero p { color: var(--muted); max-width: 620px; margin: 0 auto; font-size: 1.05rem; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 18px;
  margin-top: 28px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
  transition: transform 0.12s ease, box-shadow 0.12s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(16, 24, 40, 0.1); }
.card h2 { font-size: 1.1rem; margin: 0 0 8px; }
.card p { color: var(--muted); font-size: 0.92rem; margin: 0 0 14px; }
.card a { font-weight: 600; font-size: 0.92rem; }

.breadcrumb { font-size: 0.9rem; color: var(--muted); margin-bottom: 16px; }
.breadcrumb a { color: var(--muted); }

.calc-wrap {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
}
@media (min-width: 720px) {
  .calc-wrap { grid-template-columns: 380px 1fr; }
}

.panel {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}
.panel h2 { margin: 0 0 18px; font-size: 1.2rem; }

.field { margin-bottom: 16px; }
.field label { display: block; font-weight: 600; font-size: 0.9rem; margin-bottom: 6px; }
.field .hint { font-weight: 400; color: var(--muted); }
.field input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  font-family: inherit;
}
.field input:focus { outline: 2px solid var(--accent); border-color: var(--accent); }
.field select {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  font-family: inherit;
  background: #fff;
  color: var(--text);
}
.field select:focus { outline: 2px solid var(--accent); border-color: var(--accent); }

.units { display: flex; gap: 8px; margin-bottom: 20px; }
.unit-btn {
  flex: 1;
  padding: 9px 12px;
  border: 1px solid var(--border);
  background: #fff;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--muted);
  font-family: inherit;
}
.unit-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }

button.cta {
  width: 100%;
  padding: 12px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
}
button.cta:hover { background: var(--accent-dark); }

.results { font-size: 1rem; }
.result-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}
.result-row:last-child { border-bottom: none; }
.result-row .label { color: var(--muted); }
.result-row .value { font-weight: 700; font-size: 1.15rem; }
.result-row.primary .value { color: var(--accent); font-size: 1.4rem; }

.article { margin-top: 32px; }
.article h2 { font-size: 1.35rem; margin-top: 28px; }
.article p, .article li { color: var(--muted); }
.article ul { padding-left: 20px; }

footer {
  border-top: 1px solid var(--border);
  background: var(--card);
  padding: 28px 0;
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
}