アコーディオン：カスケード｜Accordion: Cascade

<div class="container">
    <div class="btn-box">
        <button data-default-text="Simple Cascade Accordion" data-open-text="Close">Simple Cascade Accordion</button>
    </div>
    <div class="more">
        <ul>
            <li>Simple cascade animation from top</li>
            <li>Items appear sequentially</li>
            <li>Clean and minimal design</li>
            <li>Triangle icons for open/close</li>
            <li>Smooth cascade effect</li>
        </ul>
    </div>
</div>

.container {
    margin: 20px 0;
    position: relative;
}

.btn-box button {
    width: 100%;
    padding: 15px 0;
    background: transparent;
    border: none;
    font-size: 16px;
    font-weight: 400;
    color: #333;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: left;
    position: relative;
    font-family: 'Arial', sans-serif;
}

.btn-box button::after {
    content: '▼';
    position: absolute;
    right: 0;
    top: 50%;
    transform: translateY(-50%);
    font-size: 20px;
    font-weight: 300;
    color: #666;
    transition: all 0.3s ease;
    width: 20px;
    height: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn-box button:hover {
    color: #000;
}

.btn-box button:hover::after {
    color: #000;
}

.more {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease;
    background: transparent;
}

.more.appear {
    max-height: 400px;
}

.container:has(.more.appear) .btn-box button::after {
    content: '▲';
    transform: translateY(-50%);
    color: #000;
}

.more ul {
    list-style: none;
    padding: 15px 0;
    margin: 0;
}

.more li {
    padding: 8px 0;
    color: #666;
    font-size: 14px;
    line-height: 1.6;
    opacity: 0;
    transform: translateY(-10px);
    transition: all 0.3s ease;
}

.more.appear li {
    opacity: 1;
    transform: translateY(0);
}

.more.appear li:nth-child(1) { 
    transition-delay: 0.1s; 
}
.more.appear li:nth-child(2) { 
    transition-delay: 0.2s; 
}
.more.appear li:nth-child(3) { 
    transition-delay: 0.3s; 
}
.more.appear li:nth-child(4) { 
    transition-delay: 0.4s; 
}
.more.appear li:nth-child(5) { 
    transition-delay: 0.5s; 
}

/* レスポンシブ対応 */
@media (max-width: 768px) {
    .btn-box button {
        font-size: 14px;
        padding: 12px 0;
    }
    
    .more ul {
        padding: 10px 0;
    }
    
    .more.appear {
        max-height: 300px;
    }
}

document.addEventListener('DOMContentLoaded', function() {
    const button = document.querySelector('.btn-box button');
    const more = document.querySelector('.more');
    
    button.addEventListener('click', function() {
        const isOpen = more.classList.contains('appear');
        
        more.classList.toggle('appear');
        
        // Change button text
        if (this.dataset.defaultText) {
            if (isOpen) {
                this.textContent = this.dataset.defaultText;
            } else {
                this.textContent = this.dataset.openText || 'Close';
            }
        }
    });
});