* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    background-color: #fff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    margin-bottom: 20px;
}

h1 {
    color: #2c3e50;
    margin-bottom: 20px;
    text-align: center;
}

nav {
    display: flex;
    gap: 10px;
    justify-content: center;
}

button {
    background-color: #3498db;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #2980b9;
}

.section {
    background-color: #fff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    margin-bottom: 20px;
}

.hidden {
    display: none;
}

.form-group {
    margin-bottom: 15px;
}

label {
    display: block;
    margin-bottom: 5px;
    color: #2c3e50;
}

input, select {
    width: 100%;
    padding: 8px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}

input:focus, select:focus {
    outline: none;
    border-color: #3498db;
}

.search-bar {
    margin-bottom: 20px;
}

#studentsList {
    display: grid;
    gap: 15px;
}

.student-card {
    background-color: #f8f9fa;
    padding: 15px;
    border-radius: 5px;
    border: 1px solid #ddd;
}

.student-card h3 {
    color: #2c3e50;
    margin-bottom: 10px;
}

.payment-history {
    margin-top: 10px;
    font-size: 0.9em;
    color: #666;
}

@media (max-width: 768px) {
    .container {
        padding: 10px;
    }

    nav {
        flex-direction: column;
    }

    button {
        width: 100%;
    }
}