:root {
  color-scheme: light;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f4f7fb;
  color: #1f2937;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
}

body, input, button {
  font: 16px inherit;
}

.hero {
  background: linear-gradient(135deg, #0f172a 0%, #1e3a8a 100%);
  color: #fff;
  padding: 3rem 1.5rem;
  text-align: center;
}

.hero h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(2.5rem, 5vw, 4rem);
}

.hero p {
  margin: 0 1rem auto 1rem;
  max-width: 720px;
  line-height: 1.7;
  opacity: 0.88;
}

.calculator-nav {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  justify-content: center;
}

.calculator-nav a {
  color: #e0f2fe;
  text-decoration: none;
  border: 1px solid rgba(226, 232, 240, 0.32);
  padding: 0.75rem 1.1rem;
  border-radius: 999px;
  transition: transform 0.2s ease, background 0.2s ease;
}

.calculator-nav a:hover {
  transform: translateY(-1px);
  background: rgba(255, 255, 255, 0.12);
}

.container {
  max-width: 1100px;
  margin: -2rem auto 2rem;
  padding: 0 1.5rem 2rem;
}

.card {
  background: #ffffff;
  border-radius: 24px;
  box-shadow: 0 18px 50px rgba(15, 23, 42, 0.08);
  padding: 2rem;
  margin-bottom: 1.75rem;
}

.card h2 {
  margin-top: 0;
}

.grid-form {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  margin-top: 1.25rem;
}

label {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  color: #334155;
}

input {
  width: 100%;
  border: 1px solid #cbd5e1;
  border-radius: 0.75rem;
  padding: 0.9rem 1rem;
  outline: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

input:focus {
  border-color: #2563eb;
  box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.12);
}

.action-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-top: 1.5rem;
  padding: 0.95rem 1.5rem;
  border: none;
  border-radius: 999px;
  background: #2563eb;
  color: #fff;
  cursor: pointer;
  transition: transform 0.2s ease, background 0.2s ease;
}

.action-btn:hover {
  transform: translateY(-1px);
  background: #1d4ed8;
}

..results {
  margin-top: 1.5rem;
  padding: 1.25rem;
  background: #f8fafc;
  border-radius: 1rem;
  border: 1px solid #e2e8f0;
  min-height: 4.5rem;
}

.formula {
  margin-bottom: 1rem;
  padding: 0.85rem 1rem;
  border-radius: 1rem;
  background: #eef2ff;
  border: 1px solid #c7d2fe;
  color: #1e3a8a;
  font-size: 0.95rem;
}

.conversion-box {
  padding: 1.5rem 0 0;
}

.conversion-box .grid-form {
  gap: 1rem;
  margin-bottom: 1rem;
}

#conv-to {
  background: #f8fafc;
}

.conversion-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.conversion-grid div {
  background: #f8fafc;
  border: 1px solid #e2e8f0;
  border-radius: 1rem;
  padding: 1rem;
}

.conversion-grid strong {
  display: block;
  margin-bottom: 0.5rem;
}

.footer {
  text-align: center;
  padding: 1rem 1.5rem 2rem;
  color: #94a3b8;
}


@media (max-width: 640px) {
  .hero {
    padding: 2rem 1rem;
  }
  .container {
    margin-top: 0;
  }
}