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

body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    color: #333;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
}

header {
    background: #0056b3;
    color: #fff;
    padding: 20px;
    text-align: center;
    border-radius: 5px;
    margin-bottom: 20px;
}

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

form {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

input {
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
}

button {
    padding: 10px;
    background: #28a745;
    color: #fff;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

button:hover {
    background: #218838;
}

.book-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
    border-bottom: 1px solid #eee;
}

.book-item:last-child {
    border-bottom: none;
}

.book-info {
    flex-grow: 1;
}

.action-btn {
    background: #007bff;
    margin-left: 10px;
}

.action-btn.return {
    background: #ffc107;
    color: #000;
}