body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: linear-gradient(135deg, #0f172a, #1e293b);
  color: white;
}

header {
  background: #111827;
  padding: 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

header h1 {
  color: #22c55e;
}

header a {
  color: white;
  text-decoration: none;
}

.container {
  text-align: center;
  padding: 60px 20px;
}

.calculator-card {
  background: #1e293b;
  max-width: 400px;
  margin: auto;
  padding: 30px;
  border-radius: 20px;
  box-shadow: 0 20px 40px rgba(0,0,0,0.4);
}

.calculator-card label {
  display: block;
  margin-top: 15px;
  text-align: left;
}

.calculator-card input {
  width: 100%;
  padding: 10px;
  margin-top: 5px;
  border-radius: 8px;
  border: none;
  outline: none;
}

.calculator-card button {
  margin-top: 20px;
  width: 100%;
  padding: 12px;
  background: #22c55e;
  border: none;
  border-radius: 25px;
  font-weight: bold;
  cursor: pointer;
  transition: 0.3s;
}

.calculator-card button:hover {
  background: #16a34a;
}

#result {
  margin-top: 20px;
  font-size: 18px;
  font-weight: bold;
  color: #22c55e;
}