モーダルウィンドウ：メルヘン｜Modal Window: Fairy Tale

<div class="container">
    <h1>Fairy Tale Modal</h1>
    <button id="modal-btn">Open Fairy Tale Modal</button>
</div>

<div id="mask" class="mask"></div>
<div id="modal" class="modal">
    <div class="modal-content">
        <p>【Fairy Tale Modal】</p>
        <p>A magical and dreamy modal window with pastel colors and floating particles. Perfect for creating a whimsical and enchanting atmosphere.</p>
        <div class="close-btn-container">
            <button class="close-btn">Close</button>
        </div>
    </div>
</div>

body {
    font-family: 'Arial', sans-serif;
    margin: 0;
    padding: 20px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    text-align: center;
    color: white;
}

h1 {
    margin-bottom: 30px;
    font-size: 2.5em;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

/* メルヘンモーダル */
#modal-btn {
    padding: 15px 30px;
    background: linear-gradient(45deg, #ff9a9e, #fecfef, #fecfef, #ff9a9e);
    background-size: 300% 300%;
    color: #fff;
    border: none;
    border-radius: 25px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    animation: gradientShift 3s ease infinite;
    box-shadow: 0 4px 15px rgba(255, 154, 158, 0.4);
}

@keyframes gradientShift {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

#modal-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 154, 158, 0.6);
}

#mask {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 154, 158, 0.8);
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
}

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

#modal {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0.9);
    background: linear-gradient(135deg, #ff9a9e 0%, #fecfef 50%, #fad0c4 100%);
    padding: 40px;
    border-radius: 20px;
    z-index: 1001;
    opacity: 0;
    visibility: hidden;
    transition: all 0.4s ease;
    max-width: 500px;
    width: 90%;
    box-shadow: 
        0 20px 40px rgba(255, 154, 158, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.2);
}

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

#modal p {
    color: #fff;
    line-height: 1.7;
    margin-bottom: 30px;
    font-size: 16px;
    text-align: center;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

#modal .close-btn {
    padding: 12px 24px;
    background: rgba(255, 255, 255, 0.2);
    color: #fff;
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 25px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: block;
    margin: 0 auto;
    backdrop-filter: blur(10px);
}

#modal .close-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    border-color: rgba(255, 255, 255, 0.5);
    transform: translateY(-2px);
}

/* パーティクルアニメーション */
@keyframes float {
    0%, 100% { transform: translateY(0px) rotate(0deg); opacity: 0.6; }
    50% { transform: translateY(-20px) rotate(180deg); opacity: 1; }
}

document.addEventListener('DOMContentLoaded', function() {
    const modalBtn = document.getElementById('modal-btn');
    const mask = document.getElementById('mask');
    const modal = document.getElementById('modal');
    const closeBtn = modal.querySelector('.close-btn');
    
    // モーダルを開く
    modalBtn.addEventListener('click', () => {
        mask.classList.add('appear');
        modal.classList.add('appear');
        
        // パーティクルエフェクトを追加
        createParticles(modal);
    });
    
    // マスクをクリックして閉じる
    mask.addEventListener('click', () => {
        closeModal();
    });
    
    // 閉じるボタンをクリックして閉じる
    closeBtn.addEventListener('click', () => {
        closeModal();
    });
    
    // ESCキーで閉じる
    document.addEventListener('keydown', function(e) {
        if (e.key === 'Escape') {
            closeModal();
        }
    });
    
    function closeModal() {
        mask.classList.remove('appear');
        modal.classList.remove('appear');
        clearParticles();
    }
    
    // パーティクルエフェクト作成関数
    function createParticles(modal) {
        const particlesContainer = document.createElement('div');
        particlesContainer.className = 'particles-container';
        particlesContainer.style.cssText = `
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            pointer-events: none;
            overflow: hidden;
            border-radius: 20px;
        `;
        
        for (let i = 0; i < 20; i++) {
            const particle = document.createElement('div');
            particle.className = 'particle';
            particle.style.cssText = `
                position: absolute;
                width: 4px;
                height: 4px;
                background: rgba(255, 255, 255, 0.6);
                border-radius: 50%;
                animation: float 3s ease-in-out infinite;
                animation-delay: ${Math.random() * 3}s;
            `;
            
            particle.style.left = Math.random() * 100 + '%';
            particle.style.top = Math.random() * 100 + '%';
            
            particlesContainer.appendChild(particle);
        }
        
        modal.appendChild(particlesContainer);
    }
    
    // パーティクルクリア関数
    function clearParticles() {
        const particlesContainer = document.querySelector('.particles-container');
        if (particlesContainer) {
            particlesContainer.remove();
        }
    }
});