/* =================================
   TEACHER EXEMPLAR - CSS STYLESHEET
   Computing Technology Year 10
   Demonstrates: Responsive design, accessibility, CSS Grid, Flexbox
   ================================= */

/* CSS VARIABLES - Makes colors and spacing easy to maintain */
:root {
    --primary-color: #2E7D32;
    --secondary-color: #FFA000;
    --accent-color: #1976D2;
    --text-dark: #212121;
    --text-light: #757575;
    --background: #FAFAFA;
    --card-background: #FFFFFF;
    --border-color: #E0E0E0;
    --success: #4CAF50;
    --warning: #FF9800;
    --info: #2196F3;
    
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    --border-radius: 8px;
    --box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --box-shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.15);
    
    --max-width: 1200px;
}

/* RESET & BASE STYLES */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--background);
}

/* ACCESSIBILITY - Skip link for keyboard users */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: white;
    padding: 8px 16px;
    text-decoration: none;
    border-radius: 0 0 4px 0;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

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

/* CONTAINER - Centers content and adds padding */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
}

/* HEADER */
header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #1B5E20 100%);
    color: white;
    padding: var(--spacing-xl) var(--spacing-sm);
    text-align: center;
    box-shadow: var(--box-shadow);
}

header h1 {
    font-size: clamp(1.75rem, 5vw, 2.5rem);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    line-height: 1.2;
}

.subtitle {
    font-size: clamp(1rem, 2.5vw, 1.25rem);
    opacity: 0.95;
    font-weight: 400;
    max-width: 800px;
    margin: 0 auto;
}

/* NAVIGATION CONTROLS */
.controls-nav {
    background: var(--card-background);
    border-bottom: 2px solid var(--border-color);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 50;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.controls-nav .container {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    align-items: center;
}

.filter-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
    flex: 1 1 200px;
}

.filter-group label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.filter-group select {
    padding: 0.625rem var(--spacing-sm);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: inherit;
    background: white;
    cursor: pointer;
    transition: all 0.2s ease;
}

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

.filter-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(46, 125, 50, 0.1);
}

/* BUTTONS */
.btn-secondary {
    padding: 0.625rem 1.5rem;
    background: var(--text-light);
    color: white;
    border: none;
    border-radius: var(--border-radius);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.btn-secondary:hover {
    background: var(--text-dark);
    transform: translateY(-1px);
    box-shadow: var(--box-shadow);
}

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

/* SECTIONS */
section {
    padding: var(--spacing-xl) 0;
}

section h2 {
    font-size: clamp(1.5rem, 4vw, 2rem);
    color: var(--text-dark);
    margin-bottom: var(--spacing-md);
    font-weight: 700;
}

section p {
    color: var(--text-light);
    margin-bottom: var(--spacing-md);
    max-width: 800px;
}

.lead {
    font-size: 1.125rem;
    line-height: 1.7;
    color: var(--text-dark);
}

/* INTRO SECTION WITH KEY STATS */
.intro-section {
    background: var(--card-background);
    padding: var(--spacing-xl) var(--spacing-md);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    margin: var(--spacing-lg) 0;
}

.key-stat-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.stat-card {
    background: linear-gradient(135deg, var(--primary-color), #388E3C);
    color: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    text-align: center;
    box-shadow: var(--box-shadow);
    transition: transform 0.2s ease;
}

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

.stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
    line-height: 1;
}

.stat-label {
    display: block;
    font-size: 0.875rem;
    opacity: 0.9;
    font-weight: 500;
}

/* CHART SECTIONS */
.chart-section,
.comparison-section,
.pie-section {
    background: var(--card-background);
    padding: var(--spacing-xl) var(--spacing-md);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    margin: var(--spacing-lg) 0;
}

.chart-container {
    position: relative;
    width: 100%;
    height: 400px;
    margin: var(--spacing-lg) 0;
    padding: var(--spacing-md);
    background: white;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
}

.chart-container.small {
    height: 300px;
    max-width: 500px;
    margin: var(--spacing-lg) auto;
}

/* Chart description toggle */
.chart-description {
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    background: #F5F5F5;
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-color);
}

.chart-description summary {
    cursor: pointer;
    font-weight: 600;
    color: var(--primary-color);
    user-select: none;
    list-style: none;
}

.chart-description summary::-webkit-details-marker {
    display: none;
}

.chart-description summary::before {
    content: '▶ ';
    display: inline-block;
    transition: transform 0.2s;
}

.chart-description[open] summary::before {
    transform: rotate(90deg);
}

.chart-description p {
    margin-top: var(--spacing-sm);
    color: var(--text-dark);
    line-height: 1.7;
}

/* INSIGHTS SECTION */
.insights-section {
    padding: var(--spacing-xl) var(--spacing-md);
}

.insights-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.insight-card {
    background: var(--card-background);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    border-top: 4px solid var(--primary-color);
    transition: all 0.3s ease;
}

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

.insight-card h3 {
    font-size: 1.25rem;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
}

.insight-card p {
    color: var(--text-light);
    margin-bottom: var(--spacing-md);
    font-size: 0.9375rem;
}

.insight-tag {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: rgba(46, 125, 50, 0.1);
    color: var(--primary-color);
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* TIMELINE SECTION */
.timeline-section {
    padding: var(--spacing-xl) var(--spacing-md);
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    margin: var(--spacing-lg) 0;
}

.timeline {
    position: relative;
    margin-top: var(--spacing-xl);
    padding-left: var(--spacing-lg);
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: var(--primary-color);
}

.timeline-item {
    position: relative;
    margin-bottom: var(--spacing-xl);
    padding-left: var(--spacing-lg);
}

.timeline-marker {
    position: absolute;
    left: -10px;
    top: 0;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    border: 3px solid var(--card-background);
    box-shadow: 0 0 0 3px var(--primary-color);
}

.timeline-content h3 {
    font-size: 1.125rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-xs);
}

.timeline-content p {
    color: var(--text-light);
    margin: 0;
}

/* METHODOLOGY SECTION */
.methodology-section {
    background: #F5F5F5;
    padding: var(--spacing-xl) var(--spacing-md);
    margin-top: var(--spacing-xl);
}

.methodology-details {
    background: var(--card-background);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    max-width: 800px;
    margin: var(--spacing-lg) auto 0;
}

.methodology-details dt {
    font-weight: 700;
    color: var(--text-dark);
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-xs);
}

.methodology-details dt:first-child {
    margin-top: 0;
}

.methodology-details dd {
    color: var(--text-light);
    margin-left: 0;
    padding-left: var(--spacing-md);
    border-left: 3px solid var(--primary-color);
}

/* FOOTER */
footer {
    background: var(--text-dark);
    color: white;
    padding: var(--spacing-lg) var(--spacing-sm);
    text-align: center;
    margin-top: var(--spacing-xl);
}

footer p {
    margin: var(--spacing-xs) 0;
    color: rgba(255, 255, 255, 0.8);
}

footer a {
    color: white;
    text-decoration: underline;
    transition: opacity 0.2s;
}

footer a:hover {
    opacity: 0.8;
}

/* ==============================
   RESPONSIVE DESIGN - Mobile First
   ============================== */

/* Tablet (768px and up) */
@media (min-width: 768px) {
    .container {
        padding: 0 var(--spacing-lg);
    }
    
    header {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
    
    .chart-container {
        height: 450px;
        padding: var(--spacing-lg);
    }
    
    .controls-nav .container {
        flex-wrap: nowrap;
    }
    
    .filter-group {
        flex: 0 1 auto;
    }
}

/* Desktop (1024px and up) */
@media (min-width: 1024px) {
    .chart-container {
        height: 500px;
    }
    
    .insights-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    section {
        padding: var(--spacing-xl) 0;
    }
}

/* Large Desktop (1200px and up) */
@media (min-width: 1200px) {
    :root {
        font-size: 18px;
    }
    
    .insights-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* ==============================
   PRINT STYLES
   ============================== */

@media print {
    .controls-nav,
    .skip-link,
    footer a {
        display: none;
    }
    
    body {
        background: white;
    }
    
    .chart-container {
        break-inside: avoid;
        page-break-inside: avoid;
    }
    
    .insight-card,
    .timeline-item {
        break-inside: avoid;
        page-break-inside: avoid;
    }
}

/* ==============================
   REDUCED MOTION
   ============================== */

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* ==============================
   DARK MODE SUPPORT (Optional)
   ============================== */

@media (prefers-color-scheme: dark) {
    :root {
        --text-dark: #E0E0E0;
        --text-light: #B0B0B0;
        --background: #121212;
        --card-background: #1E1E1E;
        --border-color: #333333;
    }
    
    .filter-group select {
        background: var(--card-background);
        color: var(--text-dark);
    }
    
    .chart-description {
        background: #2A2A2A;
    }
}