body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f5f5f5;
    color: #333;
    display: flex;
    justify-content: center;
    padding: 30px;
}

.container {
    background-color: #fff;
    padding: 20px 40px;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0,0,0,0.2);
    width: 500px;
}

h1, h2 {
    text-align: center;
}

.input-section, .student-list-section, .group-result-section {
    margin-bottom: 20px;
}

input, select, button {
    padding: 8px;
    margin: 5px 0;
    font-size: 14px;
}

button {
    cursor: pointer;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 5px;
}

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

ul {
    list-style-type: none;
    padding-left: 0;
}

li {
    padding: 5px 0;
    border-bottom: 1px solid #ddd;
}

.group {
    margin-bottom: 15px;
    padding: 10px;
    border: 1px solid #4CAF50;
    border-radius: 5px;
    background-color: #e8f5e9;
}