body {
  font-family: Arial, sans-serif;
  background-color: #f2f2f2;
  margin: 0;
  padding: 20px;
}

h1 {
  text-align: center;
  color: #333;
}

.calculator {
  background-color: #fff;
  border-radius: 5px;
  padding: 20px;
  margin-bottom: 20px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

label {
  display: block;
  margin-bottom: 5px;
  font-weight: bold;
  color: #333;
}

input[type="number"] {
  width: 100%;
  padding: 8px;
  border: 1px solid #ccc;
  border-radius: 3px;
}

button {
  padding: 10px 20px;
  background-color: #4caf50;
  color: #fff;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#summary-table, #amortization-table {
  background-color: #fff;
  border-radius: 5px;
  padding: 20px;
  margin-bottom: 20px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

h2 {
  color: #333;
  margin-bottom: 10px;
}

table {
 /*在给出的HTML代码基础上，我为你添加了一些CSS样式来使页面更美观且富有色彩。以下是优化后的CSS代码：

```css*/
body {
  font-family: Arial, sans-serif;
  background-color: #f2f2f2;
  margin: 0;
  padding: 20px;
}

h1 {
  text-align: center;
  color: #333;
}

.calculator {
  background-color: #fff;
  border-radius: 5px;
  padding: 20px;
  margin-bottom: 20px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

label {
  display: block;
  margin-bottom: 5px;
  font-weight: bold;
  color: #333;
}

input[type="number"] {
  width: 100%;
  padding: 8px;
  border: 1px solid #ccc;
  border-radius: 3px;
}

button {
  padding: 10px 20px;
  background-color: #4caf50;
  color: #fff;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#summary-table, #amortization-table {
  background-color: #fff;
  border-radius: 5px;
  padding: 20px;
  margin-bottom: 20px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

h2 {
  color: #333;
  margin-bottom: 10px;
}

table {
  width: 100%;
  border-collapse: collapse;
}

th, td {
  padding: 8px;
  border-bottom: 1px solid #ddd;
  text-align: left;
}

tr:hover {
  background-color: #f5f5f5;
}

#summary {
  margin-bottom: 20px;
}

#summary td:first-child {
  font-weight: bold;
  color: #333;
}

#amortization th {
  background-color: #f2f2f2;
  font-weight: bold;
  color: #333;
}
}