タブメニュー：アウトライン（モダン）｜Tab Menu: Outlined Tabs (Modern)

<div class="container">        
    <div class="tab-container">
        <ul>
            <li class="selected" data-id="tab-1">Tab 1</li>
            <li data-id="tab-2">Tab 2</li>
            <li data-id="tab-3">Tab 3</li>
        </ul>
        <div class="tab-content selected" id="tab-1">
            Good morning. This is the content of Tab 1.
        </div>
        <div class="tab-content" id="tab-2">
            Hello. This is the content of Tab 2.
        </div>
        <div class="tab-content" id="tab-3">
            Good evening. This is the content of Tab 3.
        </div>
    </div>
</div>

.container {
    max-width: 800px;
    width: 100%;
}

.tab-container {
    position: relative;
}

.tab-container ul {
    margin: 0;
    padding: 0;
    list-style: none;
    display: flex;
    border-bottom: none;
    position: relative;
    z-index: 2;
}

.tab-container ul li {
    flex: 1;
    padding: 18px 24px;
    text-align: center;
    cursor: pointer;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    color: #6c757d;
    font-weight: 500;
    letter-spacing: 0.5px;
    border: 3px solid transparent;
    border-radius: 12px 12px 0 0;
    margin: 0 2px;
    background: rgba(255, 255, 255, 0.6);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    overflow: hidden;
}

.tab-container ul li::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, 
        rgba(102, 126, 234, 0.1) 0%, 
        rgba(118, 75, 162, 0.1) 100%);
    opacity: 0;
    transition: opacity 0.4s ease;
    border-radius: 12px 12px 0 0;
}

.tab-container ul li:hover::before {
    opacity: 1;
}

.tab-container ul li.selected {
    color: #fff;
    font-weight: 600;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border: 3px solid #667eea;
    border-bottom: none;
    box-shadow: 
        0 -4px 16px rgba(102, 126, 234, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.2);
    transform: translateY(-2px);
    z-index: 3;
}

.tab-container ul li.selected::after {
    content: '';
    position: absolute;
    bottom: -3px;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, #667eea, #764ba2);
    border-radius: 0 0 3px 3px;
    box-shadow: 0 2px 8px rgba(102, 126, 234, 0.4);
}

.tab-container ul li:not(.selected):hover {
    color: #667eea;
    background: rgba(255, 255, 255, 0.9);
    border-color: rgba(102, 126, 234, 0.3);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.15);
}

.tab-content {
    display: none;
    padding: 32px;
    min-height: 180px;
    color: #495057;
    line-height: 1.7;
    border: 3px solid #667eea;
    border-top: none;
    border-radius: 0 0 16px 16px;
    background: #fff;
    position: relative;
    z-index: 2;
    margin-top: -3px;
    margin-left: 2px;
    margin-right: 2px;
}

.tab-content::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, #667eea, #764ba2, #667eea);
    border-radius: 0 0 4px 4px;
    animation: gradientFlow 3s ease-in-out infinite;
}

@keyframes gradientFlow {
    0%, 100% { 
        background: linear-gradient(90deg, #667eea, #764ba2, #667eea);
    }
    50% { 
        background: linear-gradient(90deg, #764ba2, #667eea, #764ba2);
    }
}

.tab-content.selected {
    display: block;
    animation: outlineFadeIn 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes outlineFadeIn {
    from { 
        opacity: 0; 
        transform: translateY(-15px) scale(0.98);
        filter: blur(2px);
    }
    to { 
        opacity: 1; 
        transform: translateY(0) scale(1);
        filter: blur(0);
    }
}

/* レスポンシブデザイン */
@media (max-width: 768px) {
    .tab-container ul li {
        padding: 14px 16px;
        font-size: 14px;
    }
    
    .tab-content {
        padding: 24px;
        min-height: 150px;
    }
}

document.addEventListener('DOMContentLoaded', function() {
    const tabs = document.querySelectorAll('.tab-container ul li');
    const contents = document.querySelectorAll('.tab-content');

    tabs.forEach(tab => {
        tab.addEventListener('click', function() {
            const targetId = this.getAttribute('data-id');

            // すべてのタブからselectedクラスを削除
            tabs.forEach(t => t.classList.remove('selected'));
            contents.forEach(c => c.classList.remove('selected'));

            // クリックされたタブと対応するコンテンツにselectedクラスを追加
            this.classList.add('selected');
            document.getElementById(targetId).classList.add('selected');
        });
    });
});