body {
  font-family: Arial, sans-serif;
  background-color: #0f0f0f;
  color: #f5f5f5;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.calculator-container {
  background: #1c1c1c;
  padding: 25px;
  border-radius: 12px;
  box-shadow: 0 0 12px rgba(0, 0, 0, 0.8);
  width: 350px;
}

h1 {
  text-align: center;
  margin-bottom: 20px;
  color: #00bcd4;
}

.calculator-box label {
  display: block;
  margin-top: 12px;
  font-size: 14px;
}

.calculator-box input, 
.calculator-box select {
  width: 100%;
  padding: 10px;
  margin-top: 6px;
  border-radius: 8px;
  border: none;
  outline: none;
  font-size: 14px;
  background: #2c2c2c;
  color: #fff;
}

button {
  width: 100%;
  padding: 12px;
  margin-top: 18px;
  border: none;
  border-radius: 8px;
  background: #00bcd4;
  color: #fff;
  font-size: 16px;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background: #0097a7;
}

.result-box {
  margin-top: 20px;
  padding: 15px;
  border-radius: 8px;
  background: #2c2c2c;
  text-align: center;
  font-size: 15px;
  color: #e0e0e0;
}