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

:root {
    /* Color Palette*/
    --primary-color: #4a90e2;
    --primary-hover: #357abd;
    --success-color: #27ae60;
    --danger-color: #e74c3c;
    --warning-color: #f39c12;
    --dark-bg: #1e1e2e;
    --card-bg: #2a2a3e;
    --text-primary: #ffffff;
    --text-secondary: #b0b0c3;
    --border-color: #3a3a4e;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    
    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.3);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #1e1e2e 0%, #2a2a3e 100%);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    padding: var(--spacing-sm);
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

header {
    text-align: center;
    margin-bottom: var(--spacing-lg);
    animation: fadeInDown 0.6s ease-out;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-xs);
    background: linear-gradient(135deg, #4a90e2, #27ae60);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

.task-input-section {
    margin-bottom: var(--spacing-lg);
    animation: fadeIn 0.8s ease-out;
}

.input-wrapper {
    display: flex;
    gap: var(--spacing-sm);
    background: var(--card-bg);
    padding: var(--spacing-sm);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
}

#taskInput {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--dark-bg);
    color: var(--text-primary);
    font-size: 1rem;
    transition: all 0.3s ease;
}

#taskInput:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 144, 226, 0.2);
}

#taskInput::placeholder {
    color: var(--text-secondary);
}

.btn-primary {
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    white-space: nowrap;
}

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

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

.task-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    animation: fadeIn 1s ease-out;
}

.stat-card {
    background: var(--card-bg);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: transform 0.3s ease;
}

.stat-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: var(--spacing-xs);
}

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

.filter-section {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    justify-content: center;
    flex-wrap: wrap;
}

.filter-btn {
    padding: var(--spacing-xs) var(--spacing-md);
    background: var(--card-bg);
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.95rem;
    transition: all 0.3s ease;
}

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

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

.task-list-section {
    min-height: 300px;
}

.task-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.task-item {
    background: var(--card-bg);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    animation: slideIn 0.4s ease-out;
    border-left: 4px solid var(--primary-color);
}

.task-item:hover {
    box-shadow: var(--shadow-md);
    transform: translateX(5px);
}

.task-item.completed {
    opacity: 0.7;
    border-left-color: var(--success-color);
}

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

.task-text {
    flex: 1;
    font-size: 1rem;
    color: var(--text-primary);
    transition: all 0.3s ease;
}

.task-item.completed .task-text {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.task-time {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-right: var(--spacing-sm);
}

.delete-btn {
    background: var(--danger-color);
    color: white;
    border: none;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s ease;
}

.delete-btn:hover {
    background: #c0392b;
    transform: scale(1.05);
}

.empty-state {
    text-align: center;
    padding: var(--spacing-lg);
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.empty-state.hidden {
    display: none;
}

footer {
    text-align: center;
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.footer-info {
    margin-top: var(--spacing-xs);
    font-size: 0.85rem;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

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

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@media (max-width: 768px) {
    .container {
        padding: var(--spacing-sm);
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    .input-wrapper {
        flex-direction: column;
    }
    
    .task-stats {
        grid-template-columns: 1fr;
    }
    
    .task-item {
        flex-wrap: wrap;
    }
    
    .task-time {
        width: 100%;
        margin-top: var(--spacing-xs);
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.5rem;
    }
    
    .subtitle {
        font-size: 0.95rem;
    }
    
    .filter-section {
        flex-direction: column;
    }
    
    .filter-btn {
        width: 100%;
    }

}