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

:root {
    /* Colors */
    --primary-color: #007AFF;
    --primary-dark: #0056CC;
    --primary-light: #4DA6FF;
    --secondary-color: #34C759;
    --accent-color: #FF3B30;
    --warning-color: #FF9500;
    
    /* Grays */
    --text-primary: #1D1D1F;
    --text-secondary: #6E6E73;
    --text-tertiary: #8E8E93;
    --background: #FFFFFF;
    --surface: #F2F2F7;
    --border: #D1D1D6;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #007AFF 0%, #5856D6 100%);
    --gradient-secondary: linear-gradient(135deg, #34C759 0%, #30D158 100%);
    --gradient-hero: linear-gradient(135deg, #007AFF 0%, #5856D6 50%, #AF52DE 100%);
    
    /* Spacing */
    --spacing-xs: 8px;
    --spacing-sm: 16px;
    --spacing-md: 24px;
    --spacing-lg: 32px;
    --spacing-xl: 48px;
    --spacing-2xl: 64px;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-weight-light: 300;
    --font-weight-regular: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    
    /* Sizes */
    --text-xs: 12px;
    --text-sm: 14px;
    --text-base: 16px;
    --text-lg: 18px;
    --text-xl: 20px;
    --text-2xl: 24px;
    --text-3xl: 30px;
    --text-4xl: 36px;
    --text-5xl: 48px;
    
    /* Borders */
    --border-radius-sm: 8px;
    --border-radius-md: 12px;
    --border-radius-lg: 16px;
    --border-radius-xl: 24px;
    --border-radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1), 0 2px 4px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15), 0 4px 10px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.2), 0 8px 16px rgba(0, 0, 0, 0.1);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--text-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: all 0.3s ease;
}

.navbar.scrolled {
    background: rgba(255, 255, 255, 0.98);
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 64px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    text-decoration: none;
}

.logo-img {
    width: 32px;
    height: 32px;
    border-radius: var(--border-radius-sm);
}

.logo-text {
    font-size: var(--text-lg);
    font-weight: var(--font-weight-semibold);
    color: var(--text-primary);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav-links a {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: var(--font-weight-medium);
    transition: color 0.3s ease;
    position: relative;
}

.nav-links a:hover {
    color: var(--primary-color);
}

.nav-links .download-btn {
    background: var(--gradient-primary);
    color: white;
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--border-radius-full);
    font-weight: var(--font-weight-semibold);
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
}

.nav-links .download-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    color: white;
}

/* Hero Section */
.hero {
    padding: 120px 0 var(--spacing-2xl);
    background: var(--gradient-hero);
    color: white;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('../assets/bg/bg03.jpg') center/cover;
    opacity: 0.1;
    z-index: 0;
}

.hero-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
    position: relative;
    z-index: 1;
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: var(--spacing-2xl);
    align-items: center;
    min-height: 500px;
}

.hero-text h1 {
    font-size: var(--text-5xl);
    font-weight: var(--font-weight-bold);
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}

.hero-subtitle {
    font-size: var(--text-xl);
    font-weight: var(--font-weight-light);
    margin-bottom: var(--spacing-xl);
    opacity: 0.9;
    max-width: 600px;
}

.download-buttons {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.btn-download {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(20px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--border-radius-md);
    color: white;
    text-decoration: none;
    transition: all 0.3s ease;
    font-weight: var(--font-weight-medium);
}

.btn-download:hover {
    background: rgba(255, 255, 255, 0.25);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-download i {
    font-size: var(--text-2xl);
}

.btn-download div {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.btn-download small {
    font-size: var(--text-xs);
    opacity: 0.8;
}

.btn-download strong {
    font-size: var(--text-sm);
    font-weight: var(--font-weight-semibold);
}

.hero-image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.app-icon {
    width: 200px;
    height: 200px;
    border-radius: var(--border-radius-xl);
    box-shadow: var(--shadow-xl);
    transition: transform 0.3s ease;
}

.app-icon:hover {
    transform: scale(1.05);
}

/* Section Styles */
section {
    padding: var(--spacing-2xl) 0;
}

.section-title {
    font-size: var(--text-4xl);
    font-weight: var(--font-weight-bold);
    text-align: center;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.section-subtitle {
    font-size: var(--text-lg);
    color: var(--text-secondary);
    text-align: center;
    margin-bottom: var(--spacing-xl);
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

/* Features Section */
.features {
    background: var(--surface);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.feature-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    border: 1px solid var(--border);
}

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

.feature-icon {
    width: 60px;
    height: 60px;
    background: var(--gradient-primary);
    border-radius: var(--border-radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-md);
}

.feature-icon i {
    font-size: var(--text-2xl);
    color: white;
}

.feature-card h3 {
    font-size: var(--text-xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Science Section */
.science {
    background: white;
}

.science-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-2xl);
    align-items: center;
}

.science-text h2 {
    font-size: var(--text-4xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.science-intro {
    font-size: var(--text-lg);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

.science-points {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.science-point {
    display: flex;
    gap: var(--spacing-md);
    align-items: flex-start;
}

.science-point i {
    width: 48px;
    height: 48px;
    background: var(--gradient-secondary);
    border-radius: var(--border-radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: var(--text-lg);
    flex-shrink: 0;
}

.science-point h4 {
    font-size: var(--text-lg);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

.science-point p {
    color: var(--text-secondary);
}

.learn-more-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--primary-color);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    transition: all 0.3s ease;
}

.learn-more-btn:hover {
    color: var(--primary-dark);
    gap: var(--spacing-sm);
}

.science-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.formula-card {
    background: var(--surface);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border);
}

.formula-card h4 {
    font-size: var(--text-xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-md);
    text-align: center;
    color: var(--text-primary);
}

.formula {
    font-family: 'Monaco', 'Consolas', monospace;
    background: white;
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    margin-bottom: var(--spacing-sm);
    border: 1px solid var(--border);
    color: var(--primary-color);
    font-weight: var(--font-weight-medium);
}

/* Goals Section */
.goals {
    background: var(--surface);
}

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

.goal-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    border: 1px solid var(--border);
    position: relative;
    overflow: hidden;
}

.goal-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
}

.goal-card.weight-loss::before { background: var(--gradient-primary); }
.goal-card.muscle-gain::before { background: var(--gradient-secondary); }
.goal-card.health-improvement::before { background: linear-gradient(135deg, #FF3B30 0%, #FF9500 100%); }
.goal-card.nutrition-tracking::before { background: linear-gradient(135deg, #AF52DE 0%, #5856D6 100%); }
.goal-card.weight-maintenance::before { background: linear-gradient(135deg, #32ADE6 0%, #34C759 100%); }

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

.goal-icon {
    width: 60px;
    height: 60px;
    background: var(--surface);
    border-radius: var(--border-radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-md);
    border: 2px solid var(--border);
}

.goal-icon i {
    font-size: var(--text-2xl);
    color: var(--primary-color);
}

.goal-card h3 {
    font-size: var(--text-xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.goal-card > p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
}

.goal-sublist {
    list-style: none;
    padding: 0;
}

.goal-sublist li {
    position: relative;
    padding-left: var(--spacing-md);
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
    font-size: var(--text-sm);
}

.goal-sublist li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--secondary-color);
    font-weight: var(--font-weight-bold);
}

/* Health Tracking Section */
.health-tracking {
    background: white;
}

.tracking-features {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.tracking-feature {
    display: flex;
    gap: var(--spacing-lg);
    align-items: flex-start;
}

.tracking-icon {
    width: 80px;
    height: 80px;
    border-radius: var(--border-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.tracking-icon.allergen {
    background: linear-gradient(135deg, #FF3B30 0%, #FF9500 100%);
}

.tracking-icon.vitamins {
    background: linear-gradient(135deg, #34C759 0%, #30D158 100%);
}

.tracking-icon.safety {
    background: linear-gradient(135deg, #007AFF 0%, #5856D6 100%);
}

.tracking-icon i {
    font-size: var(--text-3xl);
    color: white;
}

.tracking-info h3 {
    font-size: var(--text-2xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.tracking-info p {
    color: var(--text-secondary);
    font-size: var(--text-lg);
    line-height: 1.6;
}

/* Download Section */
.download-section {
    background: var(--surface);
    text-align: center;
}

.download-content h2 {
    font-size: var(--text-4xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.download-content p {
    font-size: var(--text-lg);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.download-buttons-large {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.btn-download-large {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    background: white;
    border: 2px solid var(--border);
    border-radius: var(--border-radius-lg);
    color: var(--text-primary);
    text-decoration: none;
    transition: all 0.3s ease;
    font-weight: var(--font-weight-medium);
    box-shadow: var(--shadow-sm);
}

.btn-download-large:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-download-large i {
    font-size: var(--text-3xl);
}

.btn-download-large.ios i {
    color: var(--text-primary);
}

.btn-download-large.android i {
    color: #34A853;
}

.download-features {
    display: flex;
    justify-content: center;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.download-feature {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--text-secondary);
}

.download-feature i {
    font-size: var(--text-xl);
    color: var(--primary-color);
}

/* Legal Section */
.legal {
    background: white;
    border-top: 1px solid var(--border);
}

.legal-content {
    display: grid;
    gap: var(--spacing-xl);
}

.disclaimer-card {
    background: rgba(255, 149, 0, 0.1);
    border: 1px solid rgba(255, 149, 0, 0.3);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
}

.disclaimer-card h3 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--text-xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--warning-color);
}

.disclaimer-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.legal-links h4 {
    font-size: var(--text-lg);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.links-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-sm);
}

.links-grid a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    transition: color 0.3s ease;
}

.links-grid a:hover {
    color: var(--primary-dark);
}

.privacy-highlight {
    background: rgba(0, 122, 255, 0.1);
    border: 1px solid rgba(0, 122, 255, 0.3);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
}

.privacy-highlight h4 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--text-lg);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--primary-color);
}

.privacy-highlight p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Footer */
.footer {
    background: var(--text-primary);
    color: white;
    padding: var(--spacing-lg) 0;
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.footer-logo-img {
    width: 32px;
    height: 32px;
    border-radius: var(--border-radius-sm);
}

.footer-text {
    opacity: 0.8;
}

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --text-5xl: 36px;
        --text-4xl: 28px;
        --text-3xl: 24px;
        --text-2xl: 20px;
        --text-xl: 18px;
    }
    
    .nav-links {
        display: none; /* Simplified for mobile */
    }
    
    .hero {
        padding: 100px 0 var(--spacing-xl);
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: var(--spacing-lg);
    }
    
    .download-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .btn-download {
        width: 200px;
        justify-content: center;
    }
    
    .app-icon {
        width: 150px;
        height: 150px;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
    
    .science-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
        text-align: center;
    }
    
    .goals-grid {
        grid-template-columns: 1fr;
    }
    
    .tracking-feature {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-md);
    }
    
    .download-buttons-large {
        flex-direction: column;
        align-items: center;
    }
    
    .download-features {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .footer-content {
        flex-direction: column;
        gap: var(--spacing-md);
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-xs);
    }
    
    .hero-text h1 {
        font-size: var(--text-4xl);
    }
    
    .section-title {
        font-size: var(--text-3xl);
    }
    
    .feature-card,
    .goal-card {
        padding: var(--spacing-md);
    }
}

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

.feature-card,
.goal-card,
.tracking-feature {
    animation: fadeInUp 0.6s ease-out;
}

/* Smooth scrolling behavior */
html {
    scroll-padding-top: 80px;
}

/* Focus styles for accessibility */
button:focus,
a:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}