タブメニュー：メタリック｜Tab Menu: Metallic

<div class="container">
    <h1>Design 18: メタリック風</h1>
    
    <div class="tab-container tab-design">
        <ul>
            <li class="selected" data-id="tab-18-1">Tab 1</li>
            <li data-id="tab-18-2">Tab 2</li>
            <li data-id="tab-18-3">Tab 3</li>
        </ul>
        <div class="tab-content selected" id="tab-18-1">
            Good morning. This is the content of Tab 1.
        </div>
        <div class="tab-content" id="tab-18-2">
            Hello. This is the content of Tab 2.
        </div>
        <div class="tab-content" id="tab-18-3">
            Good evening. This is the content of Tab 3.
        </div>
    </div>
</div>

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

h1 {
    text-align: center;
    color: #fff;
    margin-bottom: 40px;
    font-size: 2.5em;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

/* ===== デザイン: メタリック風 ===== */
.tab-design {
    overflow: hidden;
    border-radius: 12px;
    position: relative;
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
    border: 2px solid #95a5a6;
    box-shadow: 
        0 8px 32px rgba(0, 0, 0, 0.4),
        inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.tab-design::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        repeating-linear-gradient(
            45deg,
            transparent,
            transparent 10px,
            rgba(255, 255, 255, 0.03) 10px,
            rgba(255, 255, 255, 0.03) 20px
        );
    pointer-events: none;
}

.tab-design ul {
    margin: 0;
    padding: 0;
    list-style: none;
    display: flex;
    background: linear-gradient(135deg, #34495e 0%, #2c3e50 100%);
    border-radius: 12px 12px 0 0;
    overflow: hidden;
    position: relative;
    border-bottom: 2px solid #95a5a6;
}

.tab-design ul::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, 
        transparent 0%, 
        #ecf0f1 50%, 
        transparent 100%);
    animation: metallicShine 3s ease-in-out infinite;
}

@keyframes metallicShine {
    0%, 100% { opacity: 0.3; }
    50% { opacity: 1; }
}

.tab-design ul li {
    flex: 1;
    padding: 18px 24px;
    text-align: center;
    cursor: pointer;
    transition: all 0.4s ease;
    position: relative;
    color: #bdc3c7;
    font-weight: 600;
    font-family: 'Arial', sans-serif;
    font-size: 14px;
    text-transform: uppercase;
    letter-spacing: 1px;
    border-right: 1px solid #7f8c8d;
    background: linear-gradient(135deg, #34495e 0%, #2c3e50 100%);
    overflow: hidden;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
}

.tab-design ul li:last-child {
    border-right: none;
}

.tab-design ul li::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, 
        rgba(255, 255, 255, 0.1) 0%, 
        rgba(255, 255, 255, 0.05) 50%, 
        rgba(255, 255, 255, 0.1) 100%);
    opacity: 0;
    transition: opacity 0.4s ease;
}

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

.tab-design ul li.selected {
    color: #ecf0f1;
    background: linear-gradient(135deg, #e74c3c 0%, #c0392b 100%);
    box-shadow: 
        0 4px 16px rgba(231, 76, 60, 0.5),
        inset 0 2px 4px rgba(255, 255, 255, 0.2),
        inset 0 -2px 4px rgba(0, 0, 0, 0.3);
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.8);
    font-weight: 700;
    animation: metallicPulse 2s ease-in-out infinite alternate;
}

@keyframes metallicPulse {
    from { 
        box-shadow: 
            0 4px 16px rgba(231, 76, 60, 0.5),
            inset 0 2px 4px rgba(255, 255, 255, 0.2),
            inset 0 -2px 4px rgba(0, 0, 0, 0.3);
    }
    to { 
        box-shadow: 
            0 6px 20px rgba(231, 76, 60, 0.7),
            inset 0 2px 4px rgba(255, 255, 255, 0.3),
            inset 0 -2px 4px rgba(0, 0, 0, 0.4);
    }
}

.tab-design ul li.selected::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, #e74c3c, #c0392b);
    box-shadow: 0 0 10px rgba(231, 76, 60, 0.8);
}

.tab-design ul li:not(.selected):hover {
    background: linear-gradient(135deg, #3d4852 0%, #2c3e50 100%);
    color: #ecf0f1;
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.7);
    transform: translateY(-1px);
    box-shadow: 
        0 2px 8px rgba(0, 0, 0, 0.3),
        inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.tab-design .tab-content {
    display: none;
    padding: 30px;
    min-height: 180px;
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
    color: #ecf0f1;
    border-radius: 0 0 12px 12px;
    box-shadow: 
        0 4px 16px rgba(0, 0, 0, 0.4),
        inset 0 1px 0 rgba(255, 255, 255, 0.1);
    border: 1px solid #95a5a6;
    border-top: none;
    position: relative;
    overflow: hidden;
}

.tab-design .tab-content::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        repeating-linear-gradient(
            90deg,
            transparent,
            transparent 30px,
            rgba(255, 255, 255, 0.02) 30px,
            rgba(255, 255, 255, 0.02) 32px
        );
    pointer-events: none;
}

.tab-design .tab-content.selected {
    display: block;
    animation: metallicFadeIn 0.5s ease;
}

@keyframes metallicFadeIn {
    from { 
        opacity: 0; 
        transform: translateY(-15px);
        box-shadow: 
            0 2px 8px rgba(0, 0, 0, 0.4),
            inset 0 1px 0 rgba(255, 255, 255, 0.05);
    }
    to { 
        opacity: 1; 
        transform: translateY(0);
        box-shadow: 
            0 4px 16px rgba(0, 0, 0, 0.4),
            inset 0 1px 0 rgba(255, 255, 255, 0.1);
    }
}

// タブコンテナを取得
const tabContainer = document.querySelector('.tab-design');
const tabMenuItems = tabContainer.querySelectorAll('ul li');
const tabContents = tabContainer.querySelectorAll('.tab-content');

tabMenuItems.forEach(tabMenuItem => {
    tabMenuItem.addEventListener('click', () => {
        // 全てのタブからselectedクラスを外す
        tabMenuItems.forEach(item => {
            item.classList.remove('selected');
        });
        
        // クリックされたタブのみselectedクラスを付ける
        tabMenuItem.classList.add('selected');
        
        // 全てのタブのコンテンツからselectedクラスを外す
        tabContents.forEach(tabContent => {
            tabContent.classList.remove('selected');
        });

        // クリックされたタブのカスタムデータ属性と同じIDを持つコンテンツに、selectedクラスを付ける
        document.getElementById(tabMenuItem.dataset.id).classList.add('selected');
    });
});