* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  background-color: #f2f2f2;
  display: flex;
  justify-content: center;
  padding: 1rem;
  margin-top: 5rem;
}
#calculator_box {
  background-color: #ffffff;
  border-radius: 10px;
  box-shadow: 3px 4px 5px 1px rgb(195, 195, 189);
  padding: 2rem;
  font-size: 18px;
}
#calculator_box h1 {
  text-align: center;
  margin: 0.5rem 0;
}
.input_item {
  margin: 1rem 0;
}
.input_item input {
  width: 100%;
  padding: 0.5rem 0;
  margin-top: 0.2rem;
}
#calculate_btn {
  background-color: #45a049;
  border: none;
  font-size: 18px;
  font-weight: bold;
  padding: 0.5rem;
  color: #ffffff;
  width: 100%;
}
#total_amount {
  font-size: 30px;
  font-weight: bolder;
}