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

:root {
    --primary-color: #4f46e5;
    --primary-dark: #4338ca;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --bg-color: #f9fafb;
    --card-bg: #ffffff;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --border-color: #e5e7eb;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica', 'Arial', sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
}

.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.subtitle {
    opacity: 0.9;
    font-size: 1rem;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

.add-task-section {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.add-task-section h2 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-size: 1.5rem;
}

.task-form {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 1rem;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.input-field {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s;
}

.input-field:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.stats-section {
    margin-bottom: 2rem;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.stat-card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.3s;
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

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

.filter-section {
    margin-bottom: 2rem;
}

.filter-buttons {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 0.5rem 1rem;
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 500;
}

.filter-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.filter-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.tasks-section {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
}

.tasks-section h2 {
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
}

.task-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.empty-state {
    text-align: center;
    color: var(--text-secondary);
    padding: 3rem 1rem;
    font-style: italic;
}

.task-item {
    background: var(--bg-color);
    padding: 1.5rem;
    border-radius: 8px;
    border-left: 4px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 1rem;
    transition: all 0.3s;
    cursor: pointer;
}

.task-item:hover {
    box-shadow: var(--shadow);
    transform: translateX(4px);
}

.task-item.completed {
    opacity: 0.6;
    background: #f3f4f6;
}

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

.task-item.priority-high {
    border-left-color: var(--danger-color);
}

.task-item.priority-medium {
    border-left-color: var(--warning-color);
}

.task-item.priority-low {
    border-left-color: var(--success-color);
}

.task-checkbox {
    width: 24px;
    height: 24px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.task-content {
    flex: 1;
}

.task-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.task-meta {
    display: flex;
    gap: 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.task-priority {
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
}

.task-priority.high {
    background: #fee2e2;
    color: var(--danger-color);
}

.task-priority.medium {
    background: #fef3c7;
    color: var(--warning-color);
}

.task-priority.low {
    background: #d1fae5;
    color: var(--success-color);
}

.task-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-delete {
    padding: 0.5rem 1rem;
    background: var(--danger-color);
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.875rem;
    transition: all 0.3s;
}

.btn-delete:hover {
    background: #dc2626;
    transform: scale(1.05);
}

@media (max-width: 768px) {
    .task-form {
        grid-template-columns: 1fr;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .task-item {
        flex-direction: column;
        align-items: flex-start;
    }

    .task-actions {
        width: 100%;
    }
}