body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: #f5f7fb;
  margin: 0;
  padding: 20px;
}

.container {
  max-width: 520px;
  margin: auto;
  background: #ffffff;
  padding: 25px;
  border-radius: 14px;
  box-shadow: 0 15px 40px rgba(0,0,0,0.08);
  animation: fadeIn 0.5s ease;
}

.nav {
  margin-bottom: 25px;
  font-size: 14px;
}

.nav a {
  text-decoration: none;
  color: #007BFF;
  margin-right: 12px;
}

.field {
  margin-bottom: 20px;
}

label {
  font-weight: 600;
  display: block;
  margin-bottom: 6px;
}

input[type="range"] {
  width: 100%;
}

.value-display {
  font-size: 14px;
  color: #555;
  margin-top: 5px;
}

.result-box {
  background: #f0f4ff;
  padding: 18px;
  border-radius: 12px;
  margin-top: 20px;
  transition: all 0.3s ease;
}

.result {
  font-size: 26px;
  font-weight: bold;
  transition: all 0.3s ease;
}

.cta {
  margin-top: 20px;
  text-align: center;
}

button {
  width: 100%;
  padding: 14px;
  background: linear-gradient(135deg, #007BFF, #0056d2);
  color: white;
  border: none;
  border-radius: 10px;
  font-size: 16px;
  cursor: pointer;
}

@keyframes fadeIn {
  from {opacity:0; transform: translateY(10px);}
  to {opacity:1; transform: translateY(0);}
}