body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f4f7f6;
    margin: 0;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    background: #ffffff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    color: #007bff;
    margin-bottom: 20px;
}

/* 入力セクション */
.input-section {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    align-items: center;
}

#isbnInput {
    flex-grow: 1;
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    font-size: 16px;
}

button {
    padding: 10px 15px;
    background-color: #28a745;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #218838;
}

/* リスト表示エリア */
#bookList {
    list-style: none;
    padding: 0;
}

#bookList li {
    background-color: #e9f7ff;
    border-left: 5px solid #007bff;
    padding: 15px;
    margin-bottom: 10px;
    border-radius: 5px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

#bookList li strong {
    display: block;
    font-size: 1.1em;
    color: #0056b3;
}

.sort-indicator {
    float: right;
    font-size: 0.8em;
    color: #6c757d;
}