/* ========================================
   CSS Variables & Reset
   ======================================== */
:root {
    --primary-color: #1a1a2e;
    --secondary-color: #16213e;
    --accent-color: #0f3460;
    --highlight-color: #e94560;
    --text-color: #f1f1f1;
    --text-dark: #333;
    --background-light: #f8f9fa;
    --background-dark: #0a0a0a;
    --chart-bg: rgba(255, 255, 255, 0.95);
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-large: 0 10px 30px rgba(0, 0, 0, 0.2);
}

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

html {
    scroll-behavior: smooth;
}

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

h1, h2, h3, h4, h5, h6 {
    font-family: 'Playfair Display', serif;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 1rem;
}

a {
    color: var(--highlight-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

a:hover {
    color: var(--accent-color);
}

/* ========================================
   Hero Section
   ======================================== */
#hero {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 50%, var(--accent-color) 100%);
    color: var(--text-color);
    position: relative;
    overflow: hidden;
}

#hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(233, 69, 96, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(15, 52, 96, 0.1) 0%, transparent 50%);
    animation: pulse 8s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 0.5; }
    50% { opacity: 1; }
}

.hero-content {
    text-align: center;
    z-index: 1;
    max-width: 1200px;
    padding: 2rem;
}

.hero-title {
    font-size: clamp(3rem, 10vw, 7rem);
    font-weight: 900;
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: -0.02em;
    background: linear-gradient(to right, #fff, #e94560);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: fadeInUp 1s ease-out;
}

.hero-subtitle {
    font-size: clamp(1.2rem, 3vw, 2rem);
    font-weight: 300;
    margin-bottom: 3rem;
    opacity: 0.9;
    animation: fadeInUp 1s ease-out 0.2s both;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 4rem;
    margin: 3rem 0;
    flex-wrap: wrap;
    animation: fadeInUp 1s ease-out 0.4s both;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-number {
    font-size: clamp(2rem, 4vw, 3.5rem);
    font-weight: 900;
    color: var(--highlight-color);
    display: block;
}

.stat-label {
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    opacity: 0.8;
    margin-top: 0.5rem;
}

.scroll-indicator {
    position: absolute;
    bottom: 3rem;
    left: 50%;
    transform: translateX(-50%);
    text-align: center;
    animation: fadeInUp 1s ease-out 0.6s both;
}

.scroll-indicator span {
    display: block;
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    margin-bottom: 1rem;
    opacity: 0.8;
}

.scroll-arrow {
    font-size: 2rem;
    animation: bounce 2s infinite;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-10px);
    }
    60% {
        transform: translateY(-5px);
    }
}

/* ========================================
   Scrollytelling Section
   ======================================== */
#scrolly {
    position: relative;
    display: flex;
    background-color: var(--background-light);
    padding: 1rem;
}

.sticky-container {
    position: sticky;
    top: 0;
    width: 50%;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

#visualization {
    width: 100%;
    height: 90vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--chart-bg);
    border-radius: 20px;
    box-shadow: var(--shadow-large);
    padding: 2rem;
}

#chart-container {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}

article {
    width: 50%;
    padding: 0 2rem;
}

.step {
    min-height: 100vh;
    display: flex;
    align-items: center;
    opacity: 0.3;
    transition: opacity 0.5s ease;
    margin-bottom: 2rem;
}

.step.active {
    opacity: 1;
}

.step-content {
    background: white;
    padding: 3rem;
    border-radius: 15px;
    box-shadow: var(--shadow);
    max-width: 600px;
    transition: all 0.3s ease;
}

.step.active .step-content {
    box-shadow: var(--shadow-large);
    transform: scale(1.02);
}

.step-content h2 {
    font-size: clamp(1.8rem, 3vw, 2.5rem);
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.step-content h3 {
    font-size: 1.5rem;
    color: var(--secondary-color);
    margin-top: 2rem;
    margin-bottom: 1rem;
}

.step-content p {
    font-size: 1.1rem;
    margin-bottom: 1rem;
    color: #555;
    line-height: 1.8;
}

.step-content ul, .step-content ol {
    margin-left: 2rem;
    margin-bottom: 1rem;
}

.step-content li {
    margin-bottom: 0.75rem;
    line-height: 1.8;
    color: #555;
}

.step-content strong {
    color: var(--accent-color);
    font-weight: 600;
}

/* Result Boxes */
.result-box {
    background: linear-gradient(135deg, var(--accent-color), var(--highlight-color));
    color: white;
    padding: 2rem;
    border-radius: 10px;
    margin: 2rem 0;
    box-shadow: var(--shadow);
}

.result-box p {
    color: white;
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

.result-box strong {
    color: white;
    font-weight: 700;
}

/* Insight Cards */
.insight-card {
    background: linear-gradient(135deg, rgba(15, 52, 96, 0.05), rgba(233, 69, 96, 0.05));
    border-left: 4px solid var(--highlight-color);
    padding: 1.5rem;
    margin: 1.5rem 0;
    border-radius: 8px;
    transition: transform 0.3s ease;
}

.insight-card:hover {
    transform: translateX(10px);
}

.insight-card h3 {
    font-size: 1.3rem;
    color: var(--highlight-color);
    margin-bottom: 0.5rem;
}

.insight-card p {
    color: #555;
}

/* CTA Buttons */
.cta-section {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
    flex-wrap: wrap;
}

.btn-primary, .btn-secondary {
    padding: 1rem 2rem;
    border-radius: 50px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: all 0.3s ease;
    display: inline-block;
    text-align: center;
    cursor: pointer;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-color), var(--highlight-color));
    color: white;
    box-shadow: var(--shadow);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 20px rgba(233, 69, 96, 0.4);
}

.btn-secondary {
    background: transparent;
    color: var(--accent-color);
    border: 2px solid var(--accent-color);
}

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

/* ========================================
   D3 Chart Styles
   ======================================== */
.chart-title {
    font-size: 1.8rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.axis {
    font-size: 12px;
}

.axis path,
.axis line {
    stroke: #ccc;
    stroke-width: 1px;
}

.axis text {
    fill: #666;
}

.grid line {
    stroke: #e0e0e0;
    stroke-opacity: 0.5;
    shape-rendering: crispEdges;
}

.grid path {
    stroke-width: 0;
}

.dot {
    transition: all 0.3s ease;
    cursor: pointer;
}

.dot:hover {
    stroke: var(--highlight-color);
    stroke-width: 3px;
    r: 8;
}

.regression-line {
    stroke: var(--highlight-color);
    stroke-width: 3px;
    fill: none;
}

.tooltip {
    position: absolute;
    padding: 12px;
    background: rgba(0, 0, 0, 0.9);
    color: white;
    border-radius: 8px;
    pointer-events: none;
    font-size: 14px;
    box-shadow: var(--shadow-large);
    z-index: 1000;
}

.legend {
    font-size: 14px;
}

.legend-item {
    cursor: pointer;
    transition: opacity 0.3s ease;
}

.legend-item:hover {
    opacity: 0.7;
}

/* ========================================
   Footer
   ======================================== */
footer {
    background: var(--primary-color);
    color: var(--text-color);
    padding: 3rem 2rem;
    text-align: center;
}

.footer-content p {
    margin: 0.5rem 0;
    opacity: 0.8;
}

/* ========================================
   Responsive Design
   ======================================== */
@media (max-width: 1024px) {
    #scrolly {
        flex-direction: column;
    }
    
    .sticky-container {
        position: relative;
        width: 100%;
        height: 60vh;
        margin-bottom: 2rem;
    }
    
    #visualization {
        height: 100%;
    }
    
    article {
        width: 100%;
        padding: 0 1rem;
    }
    
    .step {
        min-height: 60vh;
    }
    
    .hero-stats {
        gap: 2rem;
    }
}

@media (max-width: 768px) {
    .hero-title {
        font-size: 3rem;
    }
    
    .hero-subtitle {
        font-size: 1.2rem;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 1.5rem;
    }
    
    .step-content {
        padding: 2rem;
    }
    
    #visualization {
        padding: 1rem;
    }
    
    .cta-section {
        flex-direction: column;
    }
    
    .btn-primary, .btn-secondary {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .step-content {
        padding: 1.5rem;
    }
    
    .step-content h2 {
        font-size: 1.5rem;
    }
    
    .step-content p {
        font-size: 1rem;
    }
}

/* ========================================
   Loading Animation
   ======================================== */
.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 300px;
}

.loading-spinner {
    border: 4px solid rgba(0, 0, 0, 0.1);
    border-left-color: var(--highlight-color);
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ========================================
   Print Styles
   ======================================== */
@media print {
    #hero {
        height: auto;
        padding: 2rem;
    }
    
    .sticky-container {
        position: relative;
        height: auto;
    }
    
    .step {
        opacity: 1;
        min-height: auto;
        page-break-inside: avoid;
    }
}