/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    color: #2c3e50;
    margin-bottom: 0.5em;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
}

h2 {
    font-size: 2rem;
    font-weight: 600;
}

h3 {
    font-size: 1.5rem;
    font-weight: 600;
}

h4 {
    font-size: 1.25rem;
    font-weight: 500;
}

p {
    margin-bottom: 1rem;
    color: #555;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.btn-secondary {
    background: #f8f9fa;
    color: #333;
    border: 2px solid #e9ecef;
}

.btn-secondary:hover {
    background: #e9ecef;
    transform: translateY(-2px);
}

/* Navigation */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem 0;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand h1 {
    font-size: 1.5rem;
    margin: 0;
    color: #667eea;
}

.nav-subtitle {
    font-size: 0.875rem;
    color: #666;
    font-weight: 400;
}

.nav-menu {
    display: flex;
    gap: 2rem;
}

.nav-link {
    text-decoration: none;
    color: #333;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-link:hover {
    color: #667eea;
}

.nav-toggle {
    display: none;
    font-size: 1.5rem;
    cursor: pointer;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 120px 0 80px;
    margin-top: 80px;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: white;
}

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: 1.5rem;
    opacity: 0.9;
}

.hero-description {
    font-size: 1.1rem;
    margin-bottom: 2rem;
    opacity: 0.8;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
}

.hero-buttons .btn {
    padding: 15px 30px;
    font-size: 1.1rem;
}

.hero-buttons .btn-secondary {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: 2px solid rgba(255, 255, 255, 0.3);
}

.hero-buttons .btn-secondary:hover {
    background: rgba(255, 255, 255, 0.3);
}

/* Hero Visual */
.convenience-diagram {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 2rem;
    background: rgba(255, 255, 255, 0.1);
    padding: 2rem;
    border-radius: 16px;
    backdrop-filter: blur(10px);
}

.diagram-item {
    text-align: center;
    position: relative;
}

.diagram-item i {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    display: block;
}

.diagram-item span {
    display: block;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.price-tag {
    background: #ff6b6b;
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-weight: bold;
    font-size: 0.875rem;
}

.diagram-arrow {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.diagram-arrow i {
    font-size: 2rem;
    opacity: 0.7;
}

.diagram-arrow span {
    font-size: 0.875rem;
    opacity: 0.8;
}

/* Sections */
.section {
    padding: 80px 0;
}

.section-title {
    text-align: center;
    margin-bottom: 3rem;
    font-size: 2.5rem;
}

.section-subtitle {
    text-align: center;
    font-size: 1.1rem;
    color: #666;
    margin-bottom: 3rem;
}

/* Overview Section */
.concepts-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 3rem;
}

.concept-card {
    background: #f8f9fa;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    transition: transform 0.3s ease;
}

.concept-card:hover {
    transform: translateY(-5px);
}

.concept-icon {
    width: 80px;
    height: 80px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.5rem;
    color: white;
    font-size: 2rem;
}

/* Theorem Section */
.theorem-section {
    background: #f8f9fa;
}

.theorem-statement {
    margin-bottom: 3rem;
}

.statement-box {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    border-left: 5px solid #667eea;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.theorem-text {
    font-size: 1.1rem;
    font-style: italic;
    color: #2c3e50;
    margin: 0;
}

.formula-section {
    margin-bottom: 3rem;
}

.formula-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    margin-bottom: 2rem;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.formula {
    background: #f8f9fa;
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
    margin: 1rem 0;
}

.formula-text {
    font-size: 1.25rem;
    font-family: 'Courier New', monospace;
    font-weight: bold;
    color: #2c3e50;
}

.formula-explanation {
    margin-top: 1rem;
}

.factor {
    padding: 0.5rem 0;
    border-bottom: 1px solid #eee;
}

.factor:last-child {
    border-bottom: none;
}

.pcr-interpretation {
    margin-top: 1rem;
}

.interpretation-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    margin-bottom: 0.5rem;
    border-radius: 8px;
}

.interpretation-item.good {
    background: #d4edda;
    color: #155724;
}

.interpretation-item.fair {
    background: #fff3cd;
    color: #856404;
}

.interpretation-item.poor {
    background: #f8d7da;
    color: #721c24;
}

.range {
    font-weight: bold;
}

.applications-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.application-card {
    background: white;
    padding: 1.5rem;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.application-card i {
    font-size: 2.5rem;
    color: #667eea;
    margin-bottom: 1rem;
}

/* Calculator Section */
.calculator-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    margin-top: 3rem;
}

.calculator-inputs {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.input-section {
    margin-bottom: 2rem;
}

.input-section:last-child {
    margin-bottom: 0;
}

.input-section h3 {
    color: #667eea;
    border-bottom: 2px solid #e9ecef;
    padding-bottom: 0.5rem;
    margin-bottom: 1rem;
}

.input-group {
    margin-bottom: 1rem;
}

.input-group label {
    display: block;
    font-weight: 500;
    margin-bottom: 0.5rem;
    color: #333;
}

.input-group input {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.input-group input:focus {
    outline: none;
    border-color: #667eea;
}

.input-group small {
    display: block;
    color: #666;
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

.calculator-results {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

.convenience-breakdown {
    margin-bottom: 2rem;
}

.breakdown-item {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid #eee;
}

.breakdown-total {
    display: flex;
    justify-content: space-between;
    padding: 1rem 0;
    border-top: 2px solid #667eea;
    font-weight: bold;
    font-size: 1.1rem;
}

.pcr-result {
    background: #f8f9fa;
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
    margin-bottom: 2rem;
}

.pcr-display {
    margin-bottom: 1rem;
}

.pcr-label {
    display: block;
    font-size: 0.875rem;
    color: #666;
    margin-bottom: 0.5rem;
}

.pcr-value {
    font-size: 2.5rem;
    font-weight: bold;
    color: #667eea;
}

.pcr-interpretation {
    padding: 1rem;
    border-radius: 8px;
    font-weight: 500;
}

.share-results {
    text-align: center;
}

/* Examples Section */
.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin-top: 3rem;
}

.example-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}

.example-card:hover {
    transform: translateY(-5px);
}

.example-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 1.5rem;
}

.example-header h3 {
    color: white;
    margin: 0;
}

.example-content {
    padding: 1.5rem;
}

.price-comparison {
    display: flex;
    gap: 1rem;
    margin: 1rem 0;
}

.price-item {
    background: #f8f9fa;
    padding: 0.75rem 1rem;
    border-radius: 8px;
    font-weight: bold;
    flex: 1;
    text-align: center;
}

.price-item.airport,
.price-item.highway,
.price-item.office {
    background: #fff3cd;
    color: #856404;
}

.price-item.outside,
.price-item.town,
.price-item.street {
    background: #d4edda;
    color: #155724;
}

.example-calculation ul {
    margin: 1rem 0;
    padding-left: 1.5rem;
}

.example-calculation li {
    margin-bottom: 0.5rem;
}

.pcr-result-example {
    background: #f8f9fa;
    padding: 1rem;
    border-radius: 8px;
    text-align: center;
    margin-top: 1rem;
}

.result-interpretation {
    display: block;
    margin-top: 0.5rem;
    font-weight: bold;
    padding: 0.5rem;
    border-radius: 4px;
}

.result-interpretation.good {
    background: #d4edda;
    color: #155724;
}

.result-interpretation.fair {
    background: #fff3cd;
    color: #856404;
}

.result-interpretation.poor {
    background: #f8d7da;
    color: #721c24;
}

/* About Section */
.about-section {
    background: #f8f9fa;
}

.developers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.developer-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.developer-title {
    color: #667eea;
    font-weight: 600;
    margin-bottom: 1rem;
}

.theory-background {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    margin-bottom: 3rem;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.citations {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid #eee;
}

.citations ul {
    padding-left: 1.5rem;
}

.citations li {
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    color: #666;
}

.contact-share {
    text-align: center;
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.share-buttons {
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    margin-top: 1rem;
}

.share-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: 2px solid #e9ecef;
    background: white;
    color: #333;
    text-decoration: none;
    border-radius: 8px;
    transition: all 0.3s ease;
    cursor: pointer;
    font-size: 0.9rem;
}

.share-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.share-btn[data-platform="twitter"]:hover {
    background: #1da1f2;
    color: white;
    border-color: #1da1f2;
}

.share-btn[data-platform="linkedin"]:hover {
    background: #0077b5;
    color: white;
    border-color: #0077b5;
}

.share-btn[data-platform="facebook"]:hover {
    background: #4267b2;
    color: white;
    border-color: #4267b2;
}

/* Footer */
.footer {
    background: #2c3e50;
    color: white;
    padding: 3rem 0 2rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h4 {
    color: white;
    margin-bottom: 1rem;
}

.footer-section a {
    display: block;
    color: #bdc3c7;
    text-decoration: none;
    margin-bottom: 0.5rem;
    transition: color 0.3s ease;
}

.footer-section a:hover {
    color: #667eea;
}

.footer-bottom {
    border-top: 1px solid #34495e;
    padding-top: 2rem;
    text-align: center;
    color: #bdc3c7;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
    
    .nav-toggle {
        display: block;
    }
    
    .hero .container {
        grid-template-columns: 1fr;
        gap: 2rem;
        text-align: center;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .convenience-diagram {
        flex-direction: column;
        gap: 1rem;
    }
    
    .diagram-arrow {
        transform: rotate(90deg);
    }
    
    .calculator-container {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    
    .concepts-grid,
    .examples-grid,
    .developers-grid {
        grid-template-columns: 1fr;
    }
    
    .share-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .results-header {
        flex-direction: column;
        gap: 1rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    .section {
        padding: 60px 0;
    }
    
    .hero {
        padding: 100px 0 60px;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .calculator-inputs,
    .calculator-results {
        padding: 1.5rem;
    }
}

/* Animation Classes */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: all 0.6s ease;
}

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

/* Smooth Scrolling */
html {
    scroll-behavior: smooth;
}