/* Math Tables Performance & SEO Optimized CSS */

/* CSS Variables for consistent theming and performance */
:root {
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
    --info-color: #17a2b8;
    --light-color: #f8f9fa;
    --dark-color: #343a40;
    --white: #ffffff;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    --box-shadow: 0 4px 15px rgba(0,0,0,0.1);
    --box-shadow-hover: 0 8px 25px rgba(0,0,0,0.15);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-size-base: 1rem;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.5rem;
    --font-size-xxl: 2rem;
    --line-height-base: 1.6;
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-xxl: 3rem;
}

/* Performance optimizations */
*,
*::before,
*::after {
    box-sizing: border-box;
}

/* Reduce layout shifts */
img {
    height: auto;
    max-width: 100%;
    display: block;
}

/* GPU acceleration for smooth animations */
.range-card,
.table-card,
.popular-table-card,
.study-tip-card,
.resource-card {
    will-change: transform;
    backface-visibility: hidden;
    transform: translateZ(0);
}

/* Enhanced Range Cards */
.range-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
}

.range-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    box-shadow: var(--box-shadow);
    transition: var(--transition);
    border: 1px solid #e8ecef;
    position: relative;
    overflow: hidden;
}

.range-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--info-color));
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

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

.range-card:hover::before {
    transform: scaleX(1);
}

.range-card-header {
    display: flex;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.range-icon {
    font-size: 2.5rem;
    margin-right: var(--spacing-md);
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.1));
}

.range-title {
    color: var(--dark-color);
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin: 0;
    line-height: 1.3;
}

.range-description {
    color: var(--secondary-color);
    margin-bottom: var(--spacing-md);
    line-height: var(--line-height-base);
}

.range-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.table-count {
    background: var(--light-color);
    color: var(--dark-color);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
}

.difficulty-badge {
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.difficulty-easy {
    background: #d4edda;
    color: #155724;
}

.difficulty-medium {
    background: #fff3cd;
    color: #856404;
}

.difficulty-hard {
    background: #f8d7da;
    color: #721c24;
}

/* Enhanced Popular Tables Section */
.popular-tables-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}

.popular-table-card {
    background: var(--white);
    border: 2px solid #e9ecef;
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.popular-table-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.4), transparent);
    transition: left 0.5s;
}

.popular-table-card:hover::before {
    left: 100%;
}

.popular-table-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,123,255,0.15);
}

.table-number {
    font-size: var(--font-size-lg);
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: var(--spacing-xs);
}

.table-label {
    font-size: 0.875rem;
    color: var(--secondary-color);
    margin: 0;
}

/* Enhanced Study Tips Section */
.study-tips-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
}

.study-tip-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--white);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    position: relative;
    overflow: hidden;
}

.study-tip-card::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 70%);
    transform: scale(0);
    transition: transform 0.3s ease;
}

.study-tip-card:hover::before {
    transform: scale(1);
}

.tip-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-md);
    opacity: 0.9;
}

.tip-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.tip-description {
    line-height: var(--line-height-base);
    opacity: 0.9;
}

/* Enhanced Resource Cards */
.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
}

.resource-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    text-align: center;
    box-shadow: var(--box-shadow);
    transition: var(--transition);
    border: 1px solid #e8ecef;
}

.resource-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--box-shadow-hover);
}

.resource-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
    background: linear-gradient(45deg, var(--primary-color), var(--info-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.resource-title {
    color: var(--dark-color);
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.resource-description {
    color: var(--secondary-color);
    line-height: var(--line-height-base);
    margin-bottom: var(--spacing-md);
}

/* Enhanced Buttons */
.btn-math-table {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--primary-color);
    color: var(--white);
    text-decoration: none;
    border-radius: var(--border-radius-sm);
    font-weight: 500;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.btn-math-table::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
    transition: left 0.5s;
}

.btn-math-table:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(0,123,255,0.3);
}

.btn-math-table:hover::before {
    left: 100%;
}

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

.btn-secondary:hover {
    background: #545b62;
}

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

.btn-success:hover {
    background: #1e7e34;
}

/* Interactive Table Display */
.table-display {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    box-shadow: var(--box-shadow);
    margin: var(--spacing-lg) 0;
}

.multiplication-table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-lg) 0;
}

.multiplication-table th,
.multiplication-table td {
    padding: var(--spacing-sm) var(--spacing-md);
    text-align: center;
    border: 1px solid #dee2e6;
    transition: var(--transition);
}

.multiplication-table th {
    background: var(--primary-color);
    color: var(--white);
    font-weight: 600;
}

.multiplication-table td {
    background: var(--white);
    cursor: pointer;
}

.multiplication-table td:hover {
    background: #e3f2fd;
    transform: scale(1.05);
}

.multiplication-table .highlight {
    background: #fff3e0 !important;
    font-weight: 600;
    color: var(--primary-color);
}

/* Progress Indicators */
.progress-bar {
    width: 100%;
    height: 8px;
    background: #e9ecef;
    border-radius: 4px;
    overflow: hidden;
    margin: var(--spacing-md) 0;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--success-color), var(--primary-color));
    border-radius: 4px;
    transition: width 0.3s ease;
}

/* Loading States */
.loading-skeleton {
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: loading 1.5s infinite;
}

@keyframes loading {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* Accessibility Enhancements */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Focus styles for keyboard navigation */
.range-card:focus,
.popular-table-card:focus,
.btn-math-table:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --white: #ffffff;
        --light-color: #2d2d2d;
        --dark-color: #ffffff;
        --secondary-color: #b0b0b0;
    }
    
    .range-card,
    .popular-table-card,
    .resource-card,
    .table-display {
        background: var(--white);
        border-color: #404040;
    }
    
    .multiplication-table td {
        background: var(--white);
        border-color: #404040;
    }
    
    .multiplication-table td:hover {
        background: #2d2d2d;
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --font-size-xxl: 1.75rem;
        --font-size-xl: 1.25rem;
        --spacing-xl: 1.5rem;
        --spacing-xxl: 2rem;
    }
    
    .range-grid,
    .popular-tables-grid,
    .study-tips-grid,
    .resources-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
    
    .popular-tables-grid {
        grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    }
    
    .range-card,
    .study-tip-card,
    .resource-card {
        padding: var(--spacing-lg);
    }
    
    .range-icon {
        font-size: 2rem;
    }
    
    .resource-icon {
        font-size: 2.5rem;
    }
}

@media (max-width: 480px) {
    .range-card-header {
        flex-direction: column;
        text-align: center;
    }
    
    .range-icon {
        margin-right: 0;
        margin-bottom: var(--spacing-sm);
    }
    
    .range-meta {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .multiplication-table th,
    .multiplication-table td {
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: 0.875rem;
    }
}

/* Print Styles */
@media print {
    .btn-math-table,
    .resource-card .btn-math-table {
        display: none !important;
    }
    
    .range-card,
    .popular-table-card,
    .study-tip-card,
    .resource-card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ddd;
    }
    
    .multiplication-table {
        break-inside: avoid;
    }
    
    * {
        color: #000 !important;
        background: #fff !important;
    }
}

/* Performance: Reduce motion for users who prefer it */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    .range-card,
    .popular-table-card,
    .resource-card {
        border: 2px solid;
    }
    
    .btn-math-table {
        border: 2px solid;
    }
}