/* ========================================
   RailMind.tech - Liquid Glass Design System
   ======================================== */

/* CSS Reset & Base */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #ffffff;
    background: linear-gradient(135deg, #020617 0%, #0F172A 50%, #1E293B 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

/* CSS Custom Properties */
:root {
    /* Rail/Tech Color Palette */
    --primary-blue: #0EA5E9;
    --primary-cyan: #06B6D4;
    --secondary-purple: #8B5CF6;
    --secondary-purple-light: #A78BFA;
    --accent-cyan: #22D3EE;
    --accent-pink: #EC4899;
    
    /* Background Colors */
    --bg-dark: #0F172A;
    --bg-darker: #020617;
    --bg-light: #1E293B;
    
    /* Glass Morphism */
    --glass-bg: rgba(15, 23, 42, 0.7);
    --glass-bg-light: rgba(30, 41, 59, 0.5);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-blur: blur(20px);
    
    /* Border Radius (ONLY these two allowed) */
    --radius-large: 24px;  /* rounded-2xl */
    --radius-full: 9999px; /* rounded-full */
    
    /* Spacing System (8px base unit) */
    --space-unit: 8px;
    --space-xs: calc(var(--space-unit) * 1);   /* 8px */
    --space-sm: calc(var(--space-unit) * 2);   /* 16px */
    --space-md: calc(var(--space-unit) * 3);   /* 24px */
    --space-lg: calc(var(--space-unit) * 4);   /* 32px */
    --space-xl: calc(var(--space-unit) * 6);   /* 48px */
    --space-2xl: calc(var(--space-unit) * 8);  /* 64px */
    
    /* Typography */
    --font-size-xs: 0.75rem;   /* 12px */
    --font-size-sm: 0.875rem;  /* 14px */
    --font-size-base: 1rem;    /* 16px */
    --font-size-lg: 1.125rem;  /* 18px */
    --font-size-xl: 1.25rem;   /* 20px */
    --font-size-2xl: 1.5rem;   /* 24px */
    --font-size-3xl: 1.875rem; /* 30px */
    --font-size-4xl: 2.25rem;  /* 36px */
    --font-size-5xl: 3rem;     /* 48px */
    --font-size-6xl: 3.75rem;  /* 60px */
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.15);
    --shadow-glow: 0 0 20px rgba(14, 165, 233, 0.3);
    
    /* Transitions */
    --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Glass Morphism Utility Class */
.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-large);
}

/* Typography System */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--space-md);
}

h1 {
    font-size: var(--font-size-5xl);
    background: linear-gradient(135deg, var(--primary-cyan) 0%, var(--primary-blue) 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

h2 {
    font-size: var(--font-size-4xl);
}

h3 {
    font-size: var(--font-size-2xl);
    font-weight: 600;
}

h4 {
    font-size: var(--font-size-xl);
    font-weight: 600;
}

p {
    font-size: var(--font-size-base);
    line-height: 1.8;
    margin-bottom: var(--space-md);
    color: rgba(255, 255, 255, 0.9);
}

a {
    text-decoration: none;
    color: var(--primary-cyan);
    transition: color var(--transition-base);
}

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

/* Container & Layout */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

/* Section Styling */
section {
    padding: var(--space-2xl) 0;
    position: relative;
}

.section__title {
    text-align: center;
    margin-bottom: var(--space-md);
    font-size: var(--font-size-4xl);
}

.section__subtitle {
    text-align: center;
    font-size: var(--font-size-lg);
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: var(--space-2xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Button Components */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-sm) var(--space-lg);
    font-size: var(--font-size-base);
    font-weight: 600;
    border: none;
    border-radius: var(--radius-large);
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
    white-space: nowrap;
}

.btn--primary {
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-cyan) 100%);
    color: white;
    box-shadow: var(--shadow-lg);
}

.btn--primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl), var(--shadow-glow);
}

.btn--secondary {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    color: white;
}

.btn--secondary:hover {
    background: var(--glass-bg-light);
    border-color: var(--primary-cyan);
    transform: translateY(-2px);
}

/* Input Components */
.input {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    font-size: var(--font-size-base);
    color: white;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-large);
    transition: all var(--transition-base);
}

.input::placeholder {
    color: rgba(255, 255, 255, 0.5);
}

.input:focus {
    outline: none;
    border-color: var(--primary-cyan);
    box-shadow: 0 0 0 3px rgba(6, 182, 212, 0.1);
}

/* Badge Component */
.badge {
    display: inline-block;
    padding: var(--space-xs) var(--space-sm);
    font-size: var(--font-size-sm);
    font-weight: 500;
    background: rgba(14, 165, 233, 0.2);
    border: 1px solid rgba(14, 165, 233, 0.3);
    border-radius: var(--radius-full);
    color: var(--accent-cyan);
}

/* Card Components */
.feature-card,
.step-card,
.use-case-card,
.tech-item {
    padding: var(--space-lg);
    transition: all var(--transition-base);
}

.feature-card:hover,
.use-case-card:hover,
.tech-item:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl), var(--shadow-glow);
    box-shadow: inset 0 0 20px rgba(100, 200, 255, 0.1);
}

/* Grid Layouts */
.features__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--space-lg);
}

.steps {
    display: flex;
    gap: var(--space-lg);
    justify-content: space-between;
}

.use-cases__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--space-lg);
}

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

/* Header Navigation */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: var(--space-md) 0;
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    background: rgba(2, 6, 23, 0.8);
    border-bottom: 1px solid var(--glass-border);
}

.header__container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.header__logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: white;
}

.header__logo-icon {
    font-size: var(--font-size-3xl);
}

.header__nav {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
}

.nav-link {
    font-size: var(--font-size-base);
    font-weight: 500;
    color: rgba(255, 255, 255, 0.8);
    transition: color var(--transition-base);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--accent-cyan);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-cyan), var(--primary-blue));
    border-radius: var(--radius-full);
}

.nav-link--cta {
    padding: var(--space-xs) var(--space-md);
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-cyan) 100%);
    border-radius: var(--radius-large);
    color: white;
}

.header__menu-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-xs);
}

.header__menu-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: white;
    border-radius: var(--radius-full);
    transition: all var(--transition-base);
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    padding-top: 80px;
    overflow: hidden;
}

.hero__background {
    position: absolute;
    inset: 0;
    opacity: 0.3;
    pointer-events: none;
}

.rail-network {
    width: 100%;
    height: 100%;
}

.rail-path {
    fill: none;
    stroke: var(--primary-cyan);
    stroke-width: 2;
    opacity: 0.6;
    stroke-dasharray: 10 5;
    animation: railMove 20s linear infinite;
}

@keyframes railMove {
    0% {
        stroke-dashoffset: 0;
    }
    100% {
        stroke-dashoffset: 100;
    }
}

.hero__content {
    position: relative;
    z-index: 1;
    text-align: center;
    max-width: 900px;
    padding: 0 var(--space-lg);
}

.hero__title {
    font-size: var(--font-size-6xl);
    margin-bottom: var(--space-md);
}

.hero__subtitle {
    font-size: var(--font-size-xl);
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: var(--space-xl);
    line-height: 1.6;
}

.hero__cta {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* Features Section */
.features {
    background: linear-gradient(180deg, transparent 0%, rgba(14, 165, 233, 0.05) 50%, transparent 100%);
}

.feature-card__icon {
    font-size: var(--font-size-5xl);
    margin-bottom: var(--space-md);
}

.feature-card__title {
    margin-bottom: var(--space-sm);
}

.feature-card__description {
    color: rgba(255, 255, 255, 0.7);
    font-size: var(--font-size-sm);
}

/* How It Works Section */
.how-it-works {
    background: rgba(139, 92, 246, 0.05);
}

.step-card {
    flex: 1;
    text-align: center;
}

.step-card__number {
    font-size: 4rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--secondary-purple) 0%, var(--secondary-purple-light) 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: var(--space-md);
}

.step-card__title {
    margin-bottom: var(--space-sm);
}

.step-card__description {
    color: rgba(255, 255, 255, 0.7);
    font-size: var(--font-size-sm);
}

/* Use Cases Section */
.use-case-card__icon {
    font-size: var(--font-size-4xl);
    margin-bottom: var(--space-md);
}

.use-case-card__title {
    margin-bottom: var(--space-sm);
}

.use-case-card__description {
    color: rgba(255, 255, 255, 0.7);
    font-size: var(--font-size-sm);
    margin-bottom: var(--space-md);
}

.use-case-card__features {
    list-style: none;
    padding: 0;
}

.use-case-card__features li {
    padding: var(--space-xs) 0;
    color: rgba(255, 255, 255, 0.8);
    font-size: var(--font-size-sm);
    position: relative;
    padding-left: var(--space-md);
}

.use-case-card__features li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--accent-cyan);
    font-weight: 700;
}

/* Technology Section */
.technology {
    background: linear-gradient(180deg, transparent 0%, rgba(34, 211, 238, 0.05) 50%, transparent 100%);
}

.tech-item__icon {
    font-size: var(--font-size-4xl);
    margin-bottom: var(--space-md);
}

.tech-item__title {
    margin-bottom: var(--space-sm);
}

.tech-item__description {
    color: rgba(255, 255, 255, 0.7);
    font-size: var(--font-size-sm);
    margin-bottom: var(--space-md);
}

.tech-item__badges {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-xs);
}

/* CTA Section */
.cta {
    padding: var(--space-2xl) 0;
}

.cta__content {
    max-width: 800px;
    margin: 0 auto;
    padding: var(--space-2xl);
    text-align: center;
}

.cta__title {
    margin-bottom: var(--space-md);
}

.cta__description {
    font-size: var(--font-size-lg);
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: var(--space-xl);
}

.cta__form {
    display: flex;
    gap: var(--space-md);
    max-width: 600px;
    margin: 0 auto var(--space-md);
}

.cta__form .input {
    flex: 1;
}

.cta__note {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.6);
}

/* Footer */
.footer {
    background: rgba(2, 6, 23, 0.9);
    padding: var(--space-2xl) 0 var(--space-lg);
    border-top: 1px solid var(--glass-border);
}

.footer__content {
    display: flex;
    gap: var(--space-2xl);
    margin-bottom: var(--space-xl);
}

.footer__brand {
    flex: 1;
    max-width: 400px;
}

.footer__brand-title {
    font-size: var(--font-size-2xl);
    margin-bottom: var(--space-sm);
}

.footer__brand-tagline {
    font-size: var(--font-size-lg);
    color: var(--primary-cyan);
    margin-bottom: var(--space-sm);
}

.footer__brand-description {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.6);
    line-height: 1.6;
}

.footer__links {
    display: flex;
    gap: var(--space-2xl);
    flex: 2;
}

.footer__column {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.footer__column-title {
    font-size: var(--font-size-base);
    font-weight: 600;
    margin-bottom: var(--space-xs);
    color: var(--primary-cyan);
}

.footer__link {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.7);
    transition: color var(--transition-base);
}

.footer__link:hover {
    color: var(--accent-cyan);
}

.footer__bottom {
    text-align: center;
    padding-top: var(--space-lg);
    border-top: 1px solid var(--glass-border);
}

.footer__copyright {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.5);
}

/* Animation Utilities */
.fade-in-target {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity var(--transition-slow), transform var(--transition-slow);
}

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

/* Responsive Design - Mobile First */
@media (max-width: 768px) {
    :root {
        --font-size-6xl: 2.5rem;
        --font-size-5xl: 2rem;
        --font-size-4xl: 1.75rem;
    }
    
    .header__nav {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        flex-direction: column;
        background: var(--glass-bg);
        backdrop-filter: var(--glass-blur);
        -webkit-backdrop-filter: var(--glass-blur);
        padding: var(--space-lg);
        gap: var(--space-md);
        display: none;
        border-top: 1px solid var(--glass-border);
    }
    
    .header__nav.active {
        display: flex;
    }
    
    .header__menu-toggle {
        display: flex;
    }
    
    .hero__title {
        font-size: var(--font-size-4xl);
    }
    
    .hero__subtitle {
        font-size: var(--font-size-lg);
    }
    
    .hero__cta {
        flex-direction: column;
        align-items: stretch;
    }
    
    .steps {
        flex-direction: column;
    }
    
    .features__grid,
    .use-cases__grid,
    .tech-grid {
        grid-template-columns: 1fr;
    }
    
    .cta__form {
        flex-direction: column;
    }
    
    .footer__content {
        flex-direction: column;
    }
    
    .footer__links {
        flex-direction: column;
        gap: var(--space-xl);
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    .features__grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .use-cases__grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .tech-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1025px) {
    .features__grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .use-cases__grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .tech-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}