/* 기본 스타일 리셋 */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
            line-height: 1.6;
            transition: background-color 0.3s ease, color 0.3s ease;
        }

        /* 라이트 테마 (기본) */
        body {
            background-color: #f8fafc;
            color: #1a202c;
        }

        /* 다크 테마 */
        body.dark {
            background-color: #1a202c;
            color: #e2e8f0;
        }

        .container {
            max-width: 700px;
            margin: 0 auto;
            padding: 20px;
            min-height: 100vh;
        }

        /* 헤더 스타일 */
        .header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 2rem;
            padding: 1rem 0;
        }

        .header h1 {
            font-size: 2.5rem;
            font-weight: 700;
            color: #2d3748;
        }

        body.dark .header h1 {
            color: #e2e8f0;
        }

        /* 테마 토글 버튼 */
        .theme-toggle {
            background: none;
            border: 2px solid;
            border-radius: 50%;
            width: 50px;
            height: 50px;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            transition: all 0.3s ease;
            font-size: 1.2rem;
            border-color: #4a5568;
            color: #4a5568;
            background-color: rgba(74, 85, 104, 0.1);
        }

        .theme-toggle:hover {
            background-color: rgba(74, 85, 104, 0.2);
            transform: scale(1.05);
        }

        body.dark .theme-toggle {
            border-color: #a0aec0;
            color: #a0aec0;
            background-color: rgba(160, 174, 192, 0.1);
        }

        body.dark .theme-toggle:hover {
            background-color: rgba(160, 174, 192, 0.2);
        }

        .theme-icon {
            transition: transform 0.3s ease;
        }

        .theme-toggle:hover .theme-icon {
            transform: rotate(180deg);
        }

        /* 할 일 추가 섹션 */
        .add-todo-section {
            margin-bottom: 2rem;
        }

        .add-todo-form {
            background: white;
            padding: 1.5rem;
            border-radius: 16px;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
            border: 1px solid #e2e8f0;
        }

        body.dark .add-todo-form {
            background: #2d3748;
            border-color: #4a5568;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
        }

        .form-row {
            display: flex;
            gap: 0.5rem;
            margin-bottom: 1rem;
            align-items: flex-start;
        }

        .form-row.last {
            margin-bottom: 0;
        }

        .todo-input {
            flex: 1;
            padding: 1rem 1.5rem;
            border: 2px solid #e2e8f0;
            border-radius: 12px;
            font-size: 1rem;
            outline: none;
            transition: all 0.3s ease;
            font-family: inherit;
            background-color: #ffffff;
            color: #1a202c;
        }

        .todo-input:focus {
            border-color: #4a5568;
            box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
        }

        body.dark .todo-input {
            border-color: #4a5568;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        body.dark .todo-input:focus {
            border-color: #a0aec0;
            box-shadow: 0 0 0 3px rgba(160, 174, 192, 0.1);
        }

        .memo-input {
            width: 100%;
            padding: 0.75rem 1rem;
            border: 2px solid #e2e8f0;
            border-radius: 8px;
            font-size: 0.9rem;
            outline: none;
            transition: all 0.3s ease;
            font-family: inherit;
            background-color: #ffffff;
            color: #1a202c;
            resize: vertical;
            min-height: 60px;
        }

        .memo-input:focus {
            border-color: #4a5568;
            box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
        }

        body.dark .memo-input {
            border-color: #4a5568;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        body.dark .memo-input:focus {
            border-color: #a0aec0;
            box-shadow: 0 0 0 3px rgba(160, 174, 192, 0.1);
        }

        .time-input {
            padding: 1rem;
            border: 2px solid #e2e8f0;
            border-radius: 12px;
            font-size: 1rem;
            outline: none;
            transition: all 0.3s ease;
            font-family: inherit;
            background-color: #ffffff;
            color: #1a202c;
            min-width: 140px;
            flex-shrink: 0;
        }

        .time-input:focus {
            border-color: #4a5568;
            box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
        }

        body.dark .time-input {
            border-color: #4a5568;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        body.dark .time-input:focus {
            border-color: #a0aec0;
            box-shadow: 0 0 0 3px rgba(160, 174, 192, 0.1);
        }

        .add-button {
            padding: 1rem;
            border: none;
            border-radius: 12px;
            cursor: pointer;
            font-size: 1.2rem;
            font-weight: bold;
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            justify-content: center;
            min-width: 60px;
            height: 60px;
            flex-shrink: 0;
            background-color: #4a5568;
            color: white;
        }

        .add-button:hover {
            transform: translateY(-2px);
            background-color: #2d3748;
            box-shadow: 0 8px 25px rgba(74, 85, 104, 0.3);
        }

        body.dark .add-button {
            background-color: #a0aec0;
            color: #1a202c;
        }

        body.dark .add-button:hover {
            background-color: #e2e8f0;
            box-shadow: 0 8px 25px rgba(160, 174, 192, 0.3);
        }

        .add-icon {
            font-size: 1.5rem;
            line-height: 1;
        }

        /* 백업 기능 스타일 */
        .backup-section {
            margin-bottom: 2rem;
        }

        .backup-buttons {
            display: flex;
            gap: 1rem;
            justify-content: center;
        }

        .backup-button {
            padding: 0.75rem 1.5rem;
            border: 2px solid;
            border-radius: 12px;
            cursor: pointer;
            font-size: 0.9rem;
            font-weight: 500;
            transition: all 0.3s ease;
            background: none;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .export-btn {
            border-color: #4a5568;
            color: #4a5568;
        }

        .export-btn:hover {
            background-color: rgba(74, 85, 104, 0.1);
            transform: translateY(-1px);
        }

        .import-btn {
            border-color: #38a169;
            color: #38a169;
        }

        .import-btn:hover {
            background-color: rgba(56, 161, 105, 0.1);
            transform: translateY(-1px);
        }

        body.dark .export-btn {
            border-color: #a0aec0;
            color: #a0aec0;
        }

        body.dark .export-btn:hover {
            background-color: rgba(160, 174, 192, 0.1);
        }

        body.dark .import-btn {
            border-color: #68d391;
            color: #68d391;
        }

        .auto-backup-btn {
            border-color: #e53e3e;
            color: #e53e3e;
        }

        .auto-backup-btn:hover {
            background-color: rgba(229, 62, 62, 0.1);
            transform: translateY(-1px);
        }

        .auto-backup-btn.active {
            border-color: #38a169;
            color: #38a169;
            background-color: rgba(56, 161, 105, 0.1);
        }

        body.dark .auto-backup-btn {
            border-color: #fc8181;
            color: #fc8181;
        }

        body.dark .auto-backup-btn.active {
            border-color: #68d391;
            color: #68d391;
            background-color: rgba(104, 211, 145, 0.1);
        }

        .todo-stats {
            display: flex;
            justify-content: space-between;
            padding: 1rem 1.5rem;
            margin-bottom: 1rem;
            border-radius: 12px;
            font-size: 0.9rem;
            font-weight: 500;
            background-color: #f7fafc;
            color: #4a5568;
            border: 1px solid #e2e8f0;
        }

        body.dark .todo-stats {
            background-color: #2d3748;
            color: #a0aec0;
            border: 1px solid #4a5568;
        }

        .stat-item {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 0.25rem;
        }

        .stat-label {
            font-size: 0.8rem;
            opacity: 0.8;
        }

        .stat-value {
            font-size: 1.1rem;
            font-weight: 600;
        }

        /* 할 일 목록 */
        .todo-list {
            display: flex;
            flex-direction: column;
            gap: 1rem;
        }

        .todo-item {
            background-color: #ffffff;
            border: 1px solid #e2e8f0;
            border-radius: 16px;
            padding: 1.5rem;
            transition: all 0.3s ease;
            animation: slideIn 0.3s ease;
        }

        .todo-item:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
        }

        body.dark .todo-item {
            background-color: #2d3748;
            border-color: #4a5568;
        }

        body.dark .todo-item:hover {
            box-shadow: 0 8px 25px rgba(0, 0, 0, 0.3);
        }

        .todo-item.completed {
            opacity: 0.7;
        }

        .todo-item.completed .todo-text {
            text-decoration: line-through;
        }

        .todo-main {
            display: flex;
            align-items: flex-start;
            gap: 1rem;
        }

        .todo-checkbox {
            width: 20px;
            height: 20px;
            cursor: pointer;
            accent-color: #4a5568;
            margin-top: 2px;
        }

        body.dark .todo-checkbox {
            accent-color: #a0aec0;
        }

        .todo-content {
            flex: 1;
        }

        .todo-text {
            font-size: 1.1rem;
            font-weight: 500;
            word-break: break-word;
            margin-bottom: 0.5rem;
        }

        .todo-text.editing {
            background-color: transparent;
            border: 1px solid #4a5568;
            border-radius: 6px;
            padding: 0.5rem;
            outline: none;
            font-family: inherit;
            font-size: inherit;
        }

        body.dark .todo-text.editing {
            border-color: #a0aec0;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        .todo-memo {
            font-size: 0.9rem;
            color: #718096;
            margin-bottom: 0.5rem;
            white-space: pre-wrap;
            line-height: 1.4;
        }

        body.dark .todo-memo {
            color: #a0aec0;
        }

        .todo-memo.editing {
            background-color: transparent;
            border: 1px solid #4a5568;
            border-radius: 6px;
            padding: 0.5rem;
            outline: none;
            font-family: inherit;
            font-size: inherit;
            resize: vertical;
            min-height: 60px;
            width: 100%;
        }

        body.dark .todo-memo.editing {
            border-color: #a0aec0;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        .todo-time {
            display: inline-flex;
            align-items: center;
            gap: 0.5rem;
            font-size: 0.85rem;
            color: #4a5568;
            background-color: rgba(74, 85, 104, 0.1);
            padding: 0.25rem 0.75rem;
            border-radius: 20px;
            font-weight: 500;
        }

        body.dark .todo-time {
            color: #a0aec0;
            background-color: rgba(160, 174, 192, 0.1);
        }

        .todo-time.editing {
            background: none;
            border: 1px solid #4a5568;
            border-radius: 6px;
            padding: 0.5rem;
            outline: none;
            font-family: inherit;
        }

        body.dark .todo-time.editing {
            border-color: #a0aec0;
            background-color: #1a202c;
            color: #e2e8f0;
        }

        .todo-actions {
            display: flex;
            gap: 0.5rem;
            justify-content: flex-end;
            align-items: flex-start;
            flex-shrink: 0;
        }

        .todo-button {
            background: none;
            border: none;
            cursor: pointer;
            padding: 0.5rem 1rem;
            border-radius: 8px;
            transition: all 0.2s ease;
            font-size: 0.9rem;
            font-weight: 500;
        }

        .edit-button {
            color: #4a5568;
            border: 1px solid rgba(74, 85, 104, 0.3);
        }

        .edit-button:hover {
            background-color: rgba(74, 85, 104, 0.1);
        }

        body.dark .edit-button {
            color: #a0aec0;
            border: 1px solid rgba(160, 174, 192, 0.3);
        }

        body.dark .edit-button:hover {
            background-color: rgba(160, 174, 192, 0.1);
        }

        .delete-button {
            color: #e53e3e;
            border: 1px solid rgba(229, 62, 62, 0.3);
        }

        .delete-button:hover {
            background-color: rgba(229, 62, 62, 0.1);
        }

        .save-button {
            color: #38a169;
            border: 1px solid rgba(56, 161, 105, 0.3);
        }

        .save-button:hover {
            background-color: rgba(56, 161, 105, 0.1);
        }

        .cancel-button {
            color: #718096;
            border: 1px solid rgba(113, 128, 150, 0.3);
        }

        .cancel-button:hover {
            background-color: rgba(113, 128, 150, 0.1);
        }

        /* 빈 상태 */
        .empty-state {
            text-align: center;
            padding: 4rem 2rem;
            border-radius: 16px;
            margin-top: 2rem;
            background-color: #f7fafc;
            color: #718096;
            border: 2px dashed #cbd5e0;
        }

        body.dark .empty-state {
            background-color: #2d3748;
            color: #a0aec0;
            border: 2px dashed #4a5568;
        }

        .empty-icon {
            font-size: 4rem;
            margin-bottom: 1rem;
            opacity: 0.6;
        }

        .empty-state p {
            font-size: 1.1rem;
            margin-bottom: 0.5rem;
        }

        .empty-subtitle {
            font-size: 0.9rem;
            opacity: 0.8;
        }

        /* 애니메이션 */
        @keyframes slideIn {
            from {
                opacity: 0;
                transform: translateY(-10px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        /* 반응형 디자인 */
        @media (max-width: 768px) {
            .container {
                padding: 15px;
            }
            
            .header h1 {
                font-size: 2rem;
            }
            
            .todo-stats {
                flex-direction: column;
                gap: 0.5rem;
                text-align: center;
            }
            
            .stat-item {
                flex-direction: row;
                justify-content: space-between;
            }
            
            .form-row {
                flex-wrap: wrap;
            }
            
            .todo-input {
                min-width: 0;
                width: 100%;
                order: 1;
            }
            
            .time-input {
                flex: 1;
                min-width: 120px;
                order: 2;
            }
            
            .add-button {
                order: 3;
            }
            
            .memo-input {
                order: 4;
                width: 100%;
            }
            
            .todo-actions {
                flex-direction: column;
                gap: 0.25rem;
                min-width: 80px;
            }
            
            .todo-main {
                flex-direction: column;
                gap: 0.5rem;
            }
        }

        @media (max-width: 480px) {
            .form-row {
                flex-direction: column;
            }
            
            .todo-input,
            .time-input,
            .add-button {
                width: 100%;
                order: initial;
            }
        }