/* リセットとベーススタイル */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* カラーパレット - ライトモード */
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --success-hover: #059669;
    --danger-color: #ef4444;
    --danger-hover: #dc2626;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    
    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

/* ヘッダー */
.header {
    text-align: center;
    margin-bottom: 40px;
    padding: 30px 20px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    backdrop-filter: blur(10px);
}

.title {
    font-size: 2.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 8px;
    letter-spacing: -0.5px;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-weight: 400;
}

/* メインコンテンツ */
.main-content {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 30px;
    box-shadow: var(--shadow-xl);
    backdrop-filter: blur(10px);
}

/* ドロップエリア */
.drop-area {
    border: 3px dashed var(--border-color);
    border-radius: var(--radius-md);
    padding: 60px 20px;
    text-align: center;
    margin-bottom: 30px;
    cursor: pointer;
    background: var(--bg-secondary);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.drop-area::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.1), transparent);
    transition: left 0.5s;
}

.drop-area:hover::before {
    left: 100%;
}

.drop-area:hover {
    border-color: var(--primary-color);
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.05) 0%, rgba(139, 92, 246, 0.05) 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.drop-area.drag-over {
    border-color: var(--primary-color);
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, rgba(139, 92, 246, 0.1) 100%);
    transform: scale(1.02);
    box-shadow: var(--shadow-lg);
}

.drop-area-content {
    position: relative;
    z-index: 1;
}

.drop-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    color: var(--primary-color);
    transition: var(--transition);
}

.drop-area:hover .drop-icon {
    transform: translateY(-5px) scale(1.1);
    color: var(--primary-hover);
}

.drop-text {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.drop-hint {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* コントロールエリア */
.controls {
    margin-bottom: 30px;
}

.input-group {
    margin-bottom: 20px;
}

.filename-input {
    width: 100%;
    padding: 14px 18px;
    font-size: 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-primary);
    color: var(--text-primary);
    transition: var(--transition);
    outline: none;
}

.filename-input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
    transform: translateY(-1px);
}

.filename-input::placeholder {
    color: var(--text-light);
}

.button-group {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

/* ボタン */
.btn {
    flex: 1;
    min-width: 140px;
    padding: 14px 24px;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
    color: white;
    text-transform: none;
    letter-spacing: 0.3px;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.3);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn span {
    position: relative;
    z-index: 1;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-hover) 100%);
    box-shadow: 0 4px 14px 0 rgba(99, 102, 241, 0.39);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px 0 rgba(99, 102, 241, 0.5);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-success {
    background: linear-gradient(135deg, var(--success-color) 0%, var(--success-hover) 100%);
    box-shadow: 0 4px 14px 0 rgba(16, 185, 129, 0.39);
}

.btn-success:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px 0 rgba(16, 185, 129, 0.5);
}

.btn-success:active {
    transform: translateY(0);
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger-color) 0%, var(--danger-hover) 100%);
    box-shadow: 0 4px 14px 0 rgba(239, 68, 68, 0.39);
}

.btn-danger:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px 0 rgba(239, 68, 68, 0.5);
}

.btn-danger:active {
    transform: translateY(0);
}

/* ファイルリスト */
.file-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.file-item {
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
    animation: fadeInUp 0.4s ease-out;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.file-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    transform: scaleX(0);
    transition: transform 0.3s;
}

.file-item:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.file-item:hover::before {
    transform: scaleX(1);
}

.thumbnail {
    width: 100%;
    height: 150px;
    object-fit: cover;
    border-radius: var(--radius-sm);
    margin-bottom: 12px;
    background: var(--bg-tertiary);
    transition: var(--transition);
}

.file-item:hover .thumbnail {
    transform: scale(1.05);
}

.file-item p {
    font-size: 0.875rem;
    color: var(--text-primary);
    font-weight: 500;
    word-break: break-all;
    text-align: center;
    line-height: 1.4;
    margin: 0;
}

/* レスポンシブデザイン */
@media (max-width: 768px) {
    body {
        padding: 10px;
    }
    
    .title {
        font-size: 2rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .main-content {
        padding: 20px;
    }
    
    .drop-area {
        padding: 40px 15px;
    }
    
    .drop-text {
        font-size: 1.1rem;
    }
    
    .button-group {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
    
    .file-list {
        grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
        gap: 15px;
    }
}

@media (max-width: 480px) {
    .file-list {
        grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
        gap: 12px;
    }
    
    .thumbnail {
        height: 120px;
    }
}