モーダルウィンドウ：ダーク｜Modal Window: Dark

<div class="container">
    <button class="modal-button">Dark Modal</button>
    <div class="mask"></div>
    <div class="modal">
      <div class="modal-content">
          <p>【Dark Modal】</p>
          <p>A dark-themed modal window. Easy on the eyes and suitable for nighttime use.</p>
          <div class="close-btn-container">
              <button class="close-btn">Close</button>
          </div>
      </div>
    </div>
</div>

body {
    font-family: Arial, sans-serif;
    padding: 20px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}
        
.modal-button {
    padding: 15px 30px;
    background: #1a1a1a;
    color: #fff;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.modal-button:hover {
    background: #333;
    transform: translateY(-1px);
}

.mask {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
}

.mask.appear {
    opacity: 1;
    visibility: visible;
}

.modal {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0.9);
    background: #2a2a2a;
    padding: 40px;
    border-radius: 12px;
    z-index: 1001;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    max-width: 500px;
    width: 90%;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
    border: 1px solid #444;
}

.modal.appear {
    opacity: 1;
    visibility: visible;
    transform: translate(-50%, -50%) scale(1);
}

.modal p {
    color: #ccc;
    line-height: 1.7;
    margin-bottom: 30px;
    font-size: 16px;
    text-align: center;
}

.modal .close-btn {
    padding: 12px 24px;
    background: #444;
    color: #fff;
    border: none;
    border-radius: 6px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    display: block;
    margin: 0 auto;
}

.modal .close-btn:hover {
    background: #555;
}
        
/* レスポンシブ対応 */
@media (max-width: 768px) {
    .modal {
        width: 95%;
        padding: 15px;
    }
    
    .modal p {
        font-size: 13px;
    }
    
    .modal-button {
        font-size: 13px;
        padding: 8px 16px;
    }
}

document.addEventListener('DOMContentLoaded', function() {
    const modalBtn = document.querySelector('.modal-button');
    const mask = document.querySelector('.mask');
    const modal = document.querySelector('.modal');
    const closeBtn = document.querySelector('.close-btn');
    
    // モーダルを開く
    modalBtn.addEventListener('click', () => {
        mask.classList.add('appear');
        modal.classList.add('appear');
    });
    
    // マスクをクリックして閉じる
    mask.addEventListener('click', () => {
        mask.classList.remove('appear');
        modal.classList.remove('appear');
    });
    
    // 閉じるボタンをクリックして閉じる
    closeBtn.addEventListener('click', () => {
        mask.classList.remove('appear');
        modal.classList.remove('appear');
    });
});