body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
}

/* 入力欄のフォントサイズ(iOS対策) */
input[type="number"], select {
    font-size: 16px !important;
}

.transition-all {
    transition: all 0.3s ease;
}

/* 背幅の視覚イメージ */
.spine-visual-container {
    height: 100px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: #f8f9fa;
    border-radius: 8px;
    overflow: hidden;
    perspective: 500px;
    max-width: 100%; /* スマホでの横スクロール防止 */
}

.spine-visual {
    width: 20px; /* JSで可変にする */
    height: 80px;
    background: linear-gradient(90deg, #dee2e6 0%, #ffffff 50%, #dee2e6 100%);
    border: 1px solid #ced4da;
    border-radius: 2px;
    transition: width 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 2px 2px 5px rgba(0,0,0,0.1);
}

.spine-text {
    writing-mode: vertical-rl;
    font-size: 10px;
    color: #adb5bd;
    white-space: nowrap;
    opacity: 0; /* 細いときは消す */
    transition: opacity 0.2s;
}