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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* 헤더 */
.header {
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-bottom: 30px;
    position: relative;
}

.back-button-container {
    margin-bottom: 15px;
}

.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 15px;
    background: #f8f9fa;
    color: #666;
    text-decoration: none;
    border-radius: 6px;
    font-size: 14px;
    transition: all 0.3s ease;
    border: 1px solid #e9ecef;
}

.back-btn:hover {
    background: #e9ecef;
    color: #333;
    transform: translateX(-2px);
}

.project-title {
    font-size: 28px;
    color: #2c3e50;
    display: flex;
    align-items: center;
    gap: 12px;
}

.project-title i {
    color: #3498db;
}

/* TodoList 앱 */
.todo-app {
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-bottom: 30px;
}

.todo-header {
    text-align: center;
    margin-bottom: 30px;
}

.todo-header h2 {
    color: #2c3e50;
    font-size: 24px;
    margin-bottom: 10px;
}

.todo-header p {
    color: #666;
    font-size: 16px;
}

/* 입력 폼 */
.todo-input-section {
    margin-bottom: 25px;
}

.todo-form {
    display: flex;
    gap: 10px;
}

.input-group {
    display: flex;
    flex: 1;
    gap: 10px;
}

#todoInput {
    flex: 1;
    padding: 12px 15px;
    border: 2px solid #e9ecef;
    border-radius: 6px;
    font-size: 16px;
    transition: border-color 0.3s ease;
}

#todoInput:focus {
    outline: none;
    border-color: #3498db;
}

.add-btn {
    padding: 12px 20px;
    background: #3498db;
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 16px;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.add-btn:hover {
    background: #2980b9;
    transform: translateY(-2px);
}

/* 필터 버튼 */
.todo-filters {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 25px;
}

.filter-btn {
    padding: 8px 16px;
    background: #f8f9fa;
    border: 1px solid #e9ecef;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 14px;
}

.filter-btn.active {
    background: #3498db;
    color: white;
    border-color: #3498db;
}

.filter-btn:hover:not(.active) {
    background: #e9ecef;
}

/* 할 일 목록 */
.todo-list {
    margin-bottom: 25px;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 8px;
    margin-bottom: 10px;
    transition: all 0.3s ease;
    border: 1px solid #e9ecef;
}

.todo-item:hover {
    transform: translateX(5px);
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.todo-item.completed {
    opacity: 0.7;
    background: #e8f5e8;
}

.todo-checkbox {
    margin-right: 15px;
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.todo-text {
    flex: 1;
    font-size: 16px;
    color: #333;
}

.todo-item.completed .todo-text {
    text-decoration: line-through;
    color: #666;
}

.todo-delete {
    background: #e74c3c;
    color: white;
    border: none;
    border-radius: 4px;
    padding: 8px 12px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 14px;
}

.todo-delete:hover {
    background: #c0392b;
    transform: scale(1.1);
}

/* 통계 */
.todo-stats {
    display: flex;
    justify-content: space-around;
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 25px;
}

.stat-item {
    text-align: center;
}

.stat-label {
    display: block;
    font-size: 14px;
    color: #666;
    margin-bottom: 5px;
}

.stat-value {
    display: block;
    font-size: 24px;
    font-weight: bold;
    color: #2c3e50;
}

/* 액션 버튼 */
.todo-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
}

.action-btn {
    padding: 10px 20px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 14px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.clear-completed {
    background: #f39c12;
    color: white;
}

.clear-completed:hover {
    background: #e67e22;
}

.clear-all {
    background: #e74c3c;
    color: white;
}

.clear-all:hover {
    background: #c0392b;
}

/* 섹션 공통 스타일 */
section {
    background: white;
    padding: 25px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-bottom: 25px;
}

section h2 {
    color: #2c3e50;
    margin-bottom: 20px;
    font-size: 22px;
}

/* 프로젝트 정보 */
.info-card {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    border-left: 4px solid #3498db;
}

.info-card h2 {
    color: #2c3e50;
    margin-bottom: 15px;
}

.info-card p {
    color: #666;
    margin-bottom: 20px;
    font-size: 16px;
}

.tech-stack h3 {
    color: #2c3e50;
    margin-bottom: 12px;
    font-size: 18px;
}

.tech-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.tech-tag {
    background: #3498db;
    color: white;
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 500;
}

/* 기능 목록 */
.feature-list {
    display: grid;
    gap: 20px;
}

.feature-item {
    display: flex;
    align-items: flex-start;
    gap: 15px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 8px;
    border: 1px solid #e9ecef;
}

.feature-item i {
    font-size: 24px;
    color: #3498db;
    margin-top: 2px;
}

.feature-content h3 {
    color: #2c3e50;
    margin-bottom: 8px;
    font-size: 16px;
}

.feature-content p {
    color: #666;
    font-size: 14px;
}

/* 반응형 디자인 */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }
    
    .project-title {
        font-size: 24px;
    }
    
    .todo-app {
        padding: 20px;
    }
    
    .todo-form {
        flex-direction: column;
    }
    
    .input-group {
        flex-direction: column;
    }
    
    .todo-filters {
        flex-wrap: wrap;
    }
    
    .todo-stats {
        flex-direction: column;
        gap: 15px;
    }
    
    .todo-actions {
        flex-direction: column;
    }
    
    .feature-item {
        flex-direction: column;
        text-align: center;
    }
}