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

:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --success: #10b981;
    --danger: #ef4444;
    --text: #1f2937;
    --text-light: #6b7280;
    --border: #e5e7eb;
    --bg: #ffffff;
    --bg-secondary: #f9fafb;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
}

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

#fireworks {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 1;
}

header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem;
    box-shadow: var(--shadow-lg);
    position: relative;
    z-index: 10;
}

.header-content {
    max-width: 600px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

h1 {
    font-size: 1.75rem;
    color: var(--primary);
    font-weight: 700;
}

.built-with {
    font-size: 0.75rem;
    color: var(--text-light);
    text-decoration: none;
    transition: color 0.2s;
}

.built-with:hover {
    color: var(--primary);
}

.container {
    max-width: 600px;
    margin: 2rem auto;
    padding: 0 1rem;
    position: relative;
    z-index: 5;
}

.input-section {
    background: var(--bg);
    border-radius: 1rem;
    padding: 1.5rem;
    box-shadow: var(--shadow-lg);
    margin-bottom: 1.5rem;
}

.input-group {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

#taskInput {
    flex: 1;
    padding: 0.875rem 1rem;
    border: 2px solid var(--border);
    border-radius: 0.75rem;
    font-size: 1rem;
    transition: all 0.2s;
    background: var(--bg-secondary);
}

#taskInput:focus {
    outline: none;
    border-color: var(--primary);
    background: var(--bg);
}

#addBtn {
    padding: 0.875rem 1.25rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 0.75rem;
    font-size: 1.25rem;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 50px;
}

#addBtn:hover {
    background: var(--primary-dark);
    transform: scale(1.05);
}

#addBtn:active {
    transform: scale(0.95);
}

.stats {
    display: flex;
    gap: 1.5rem;
    font-size: 0.875rem;
    color: var(--text-light);
}

.filter-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    background: rgba(255, 255, 255, 0.9);
    padding: 0.5rem;
    border-radius: 0.75rem;
}

.filter-btn {
    flex: 1;
    padding: 0.625rem;
    border: none;
    background: transparent;
    color: var(--text-light);
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.2s;
    font-weight: 500;
}

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

.filter-btn:hover:not(.active) {
    background: var(--bg-secondary);
}

.task-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

.task-item {
    background: rgba(255, 255, 255, 0.95);
    padding: 1rem;
    border-radius: 0.75rem;
    display: flex;
    align-items: flex-start;
    gap: 0.875rem;
    transition: all 0.2s;
    animation: slideIn 0.3s ease-out;
}

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

.task-item:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.task-checkbox {
    width: 1.5rem;
    height: 1.5rem;
    border: 2px solid var(--border);
    border-radius: 0.375rem;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
    flex-shrink: 0;
    margin-top: 0.125rem;
}

.task-checkbox:hover {
    border-color: var(--primary);
}

.task-checkbox.checked {
    background: var(--success);
    border-color: var(--success);
}

.task-checkbox.checked::after {
    content: '✓';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 1rem;
}

.task-content {
    flex: 1;
}

.task-text {
    font-size: 1rem;
    margin-bottom: 0.25rem;
    word-break: break-word;
}

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

.task-timestamps {
    font-size: 0.75rem;
    color: var(--text-light);
    display: flex;
    flex-direction: column;
    gap: 0.125rem;
}

.timestamp {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.delete-btn {
    background: var(--danger);
    color: white;
    border: none;
    padding: 0.375rem 0.75rem;
    border-radius: 0.375rem;
    cursor: pointer;
    font-size: 0.875rem;
    transition: all 0.2s;
    opacity: 0.8;
}

.delete-btn:hover {
    opacity: 1;
    transform: scale(1.05);
}

.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: white;
    display: none;
}

.empty-state.show {
    display: block;
}

.empty-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.actions {
    display: flex;
    justify-content: center;
    margin-top: 2rem;
}

.clear-btn {
    background: rgba(255, 255, 255, 0.9);
    color: var(--danger);
    border: 2px solid var(--danger);
    padding: 0.75rem 1.5rem;
    border-radius: 0.75rem;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.2s;
}

.clear-btn:hover {
    background: var(--danger);
    color: white;
}

footer {
    text-align: center;
    padding: 2rem 1rem;
    color: white;
    font-size: 0.875rem;
}

@media (max-width: 480px) {
    h1 {
        font-size: 1.5rem;
    }
    
    .built-with {
        display: none;
    }
    
    .input-section {
        padding: 1rem;
    }
    
    .stats {
        font-size: 0.75rem;
    }
}