/* Main Layout Styles */

body {
    font-family: var(--font-body);
    font-size: var(--font-size-base);
    color: var(--color-text);
    background-color: var(--color-background);
    line-height: var(--line-height-normal);
}

/* Skip Link for Accessibility */
.skip-link {
    position: absolute;
    top: -100px;
    left: 0;
    background: var(--color-primary);
    color: var(--color-text);
    padding: var(--spacing-md);
    text-decoration: none;
    font-weight: var(--font-weight-bold);
    z-index: var(--z-tooltip);
    transition: top var(--transition-fast);
}

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

/* Container */
.container {
    max-width: var(--container-width-lg);
    margin: 0 auto;
    padding: 0 var(--spacing-xl);
}

/* Header & Navigation */
.site-header {
    position: sticky;
    top: 0;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    z-index: var(--z-sticky);
    transition: box-shadow var(--transition-base);
}

.site-header:hover {
    box-shadow: var(--shadow-md);
}

.main-navigation {
    padding: var(--spacing-md) 0;
}

.main-navigation ul {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--spacing-lg);
    flex-wrap: wrap;
}

.main-navigation a {
    padding: var(--spacing-sm) var(--spacing-md);
    font-family: var(--font-heading);
    font-weight: var(--font-weight-medium);
    font-size: var(--font-size-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text);
    transition: color var(--transition-base), transform var(--transition-base);
    position: relative;
}

.main-navigation a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%) scaleX(0);
    width: 80%;
    height: 2px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
    transition: transform var(--transition-base);
}

.main-navigation a:hover,
.main-navigation a:focus {
    color: var(--color-secondary);
    transform: translateY(-2px);
}

.main-navigation a:hover::after,
.main-navigation a:focus::after,
.main-navigation a.active::after {
    transform: translateX(-50%) scaleX(1);
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, 
        var(--color-primary) 0%, 
        var(--color-secondary) 50%,
        var(--color-accent) 100%);
    text-align: center;
    padding: var(--spacing-4xl) var(--spacing-xl);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(circle at 30% 50%, rgba(255, 255, 255, 0.1) 0%, transparent 50%);
    animation: pulse 8s ease-in-out infinite;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 900px;
}

.hero-title {
    font-family: var(--font-heading);
    font-size: var(--font-size-6xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-white);
    margin-bottom: var(--spacing-lg);
    text-shadow: 2px 4px 8px rgba(0, 0, 0, 0.2);
    animation: fadeInUp 1s ease-out;
    letter-spacing: 0.02em;
}

.hero-subtitle {
    font-size: var(--font-size-2xl);
    color: var(--color-white);
    margin-bottom: var(--spacing-xl);
    animation: fadeInUp 1s ease-out 0.3s backwards;
    font-weight: var(--font-weight-normal);
    text-shadow: 1px 2px 4px rgba(0, 0, 0, 0.15);
}

.hero-definition {
    background: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    padding: var(--spacing-lg) var(--spacing-xl);
    border-radius: var(--radius-lg);
    animation: fadeInUp 1s ease-out 0.6s backwards;
    border: 2px solid rgba(255, 255, 255, 0.3);
}

.hero-definition p {
    font-size: var(--font-size-xl);
    color: var(--color-white);
    font-style: italic;
    font-weight: var(--font-weight-medium);
    margin: 0;
}

/* Content Sections */
.content-section {
    padding: var(--section-padding);
    min-height: 60vh;
    position: relative;
}

.content-section:nth-child(even) {
    background-color: var(--color-background-alt);
}

.content-section h2 {
    font-family: var(--font-heading);
    font-size: var(--font-size-4xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-2xl);
    color: var(--color-text);
    position: relative;
    display: inline-block;
}

.content-section h2::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 0;
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
    border-radius: var(--radius-full);
}

.content-section h3 {
    font-family: var(--font-heading);
    font-size: var(--font-size-2xl);
    font-weight: var(--font-weight-medium);
    margin-bottom: var(--spacing-lg);
    color: var(--color-secondary);
}

.content-section h4 {
    font-family: var(--font-heading);
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-medium);
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.content-section p {
    margin-bottom: var(--spacing-lg);
    line-height: var(--line-height-relaxed);
    color: var(--color-text);
}

.section-intro {
    font-size: var(--font-size-lg);
    color: var(--color-text-light);
    max-width: 800px;
    margin-bottom: var(--spacing-3xl);
    line-height: var(--line-height-relaxed);
}

/* Lists */
ul {
    list-style: none;
    padding-left: 0;
}

.content-section ul li {
    padding-left: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    position: relative;
}

.content-section ul li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--color-primary);
    font-weight: var(--font-weight-bold);
}

/* Footer */
.site-footer {
    background: linear-gradient(135deg, var(--color-text) 0%, #1a1d23 100%);
    color: var(--color-white);
    padding: var(--spacing-4xl) var(--spacing-xl);
}

.site-footer h2 {
    color: var(--color-primary);
    margin-bottom: var(--spacing-2xl);
}

.references {
    margin: var(--spacing-2xl) 0;
    padding: 0;
}

.references li {
    margin-bottom: var(--spacing-md);
    padding-left: var(--spacing-lg);
    position: relative;
    line-height: var(--line-height-relaxed);
    color: var(--color-text-lighter);
}

.references li::before {
    content: '📚';
    position: absolute;
    left: 0;
}

.footer-info {
    margin-top: var(--spacing-3xl);
    padding-top: var(--spacing-2xl);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
}

.footer-info p {
    margin-bottom: var(--spacing-md);
    color: var(--color-text-lighter);
}

.copyright {
    font-size: var(--font-size-sm);
    opacity: 0.7;
}

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

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

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-50px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(50px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* Scroll animations */
.content-section {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.content-section.fade-in {
    opacity: 1;
    transform: translateY(0);
}

/* Focus visible for accessibility */
*:focus-visible {
    outline: 3px solid var(--color-primary);
    outline-offset: 2px;
}