body {
    font-family: 'Arial', sans-serif;
    background-color: #f0f0f0;
    color: #333;
    margin: 0;
    padding: 0;
}

.container {
    width: 90%;
    margin: 20px auto;
    padding: 20px;
    background-color: #fff;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    color: #555;
}

.controls {
    margin-bottom: 20px;
}

.controls button {
    margin-right: 10px;
    padding: 10px;
    background-color: #4CAF50;
    color: white;
    border: none;
    cursor: pointer;
}

.controls button:hover {
    background-color: #45a049;
}

.class-selector {
    margin-bottom: 20px;
}

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

table, th, td {
    border: 1px solid #ddd;
}

th, td {
    padding: 10px;
    text-align: left;
}

th {
    background-color: #4CAF50;
    color: white;
}

tr:nth-child(even) {
    background-color: #f2f2f2;
}

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

button {
    padding: 5px 10px;
    margin: 2px;
    cursor: pointer;
}