/* Traceability: STK-FRONTEND-002 (CSS3 with Flexbox, Grid, Custom Properties) */

/* ===================================
   CSS CUSTOM PROPERTIES (DESIGN TOKENS)
   =================================== */
:root {
    /* Colors - Empowering palette */
    --color-primary: #FF6B35;        /* Bold orange - energy */
    --color-primary-dark: #E85A2A;   /* Darker orange for hover */
    --color-secondary: #004E89;      /* Deep blue - stability */
    --color-accent: #F7931E;         /* Bright accent */
    --color-dark: #1A1A2E;           /* Near black */
    --color-text: #333333;           /* Body text */
    --color-text-light: #666666;     /* Secondary text */
    --color-bg: #FFFFFF;             /* White background */
    --color-bg-alt: #F8F9FA;         /* Alternate background */
    
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-weight-normal: 400;
    --font-weight-bold: 700;
    --font-weight-black: 900;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 3rem;
    --spacing-xl: 4rem;
    --spacing-xxl: 6rem;
    
    /* Breakpoints (for reference in media queries) */
    --breakpoint-mobile: 768px;
    --breakpoint-tablet: 1024px;
}

/* ===================================
   RESET & BASE STYLES
   =================================== */
/* Traceability: STK-FRONTEND-001 (HTML5 standard) */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    /* Traceability: FUN-LAYOUT-004 (Smooth scroll behavior) */
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-primary);
    color: var(--color-text);
    background-color: var(--color-bg);
    line-height: 1.6;
    /* Traceability: FUN-LAYOUT-003 (Fast load time optimization) */
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ===================================
   CONTAINER
   =================================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===================================
   HERO SECTION
   =================================== */
/* Traceability: FUN-HERO-007 (Hero visible on load) */
.hero-section {
    min-height: 100vh;
    /* Traceability: STK-FRONTEND-009 (Flexbox for responsive layout) */
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    background: linear-gradient(135deg, var(--color-secondary) 0%, var(--color-dark) 100%);
    color: var(--color-bg);
    padding: var(--spacing-xl) var(--spacing-md);
}

/* Traceability: FUN-HERO-001, FUN-HERO-006 (Product name, bold typography) */
.product-name {
    font-size: clamp(3rem, 8vw, 6rem);
    font-weight: var(--font-weight-black);
    letter-spacing: -0.02em;
    margin-bottom: var(--spacing-sm);
    /* Empowering energy through bold typography */
    text-transform: uppercase;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Traceability: FUN-HERO-002 (Tagline) */
.tagline {
    font-size: clamp(1.5rem, 3vw, 2.5rem);
    font-weight: var(--font-weight-bold);
    color: var(--color-bg);
    margin-bottom: var(--spacing-lg);
    letter-spacing: 0.02em;
}

/* Traceability: FUN-HERO-003, FUN-HERO-004, FUN-HERO-005 (Product description) */
.product-description {
    max-width: 800px;
    margin: 0 auto;
}

.description-main {
    font-size: clamp(1.125rem, 2vw, 1.5rem);
    margin-bottom: var(--spacing-md);
    color: rgba(255, 255, 255, 0.95);
}

.description-audience {
    font-size: clamp(1rem, 1.5vw, 1.25rem);
    margin-bottom: var(--spacing-sm);
    color: rgba(255, 255, 255, 0.85);
}

.description-license {
    font-size: clamp(0.875rem, 1.25vw, 1.125rem);
    color: rgba(255, 255, 255, 0.75);
}

/* ===================================
   FEATURES SECTION
   =================================== */
/* Traceability: FUN-FEATURES-010 (Below hero) */
.features-section {
    padding: var(--spacing-xxl) var(--spacing-md);
    background-color: var(--color-bg-alt);
}

.section-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: var(--font-weight-black);
    text-align: center;
    color: var(--color-dark);
    margin-bottom: var(--spacing-xl);
}

/* Traceability: FUN-FEATURES-006, FUN-FEATURES-007, STK-FRONTEND-009 (Grid layout) */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    max-width: 1200px;
    margin: 0 auto;
}

/* Traceability: FUN-FEATURES-001 (Feature cards) */
.feature-card {
    background: var(--color-bg);
    padding: var(--spacing-lg);
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.15);
}

.feature-icon {
    font-size: 3rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-md);
}

.feature-title {
    font-size: 1.5rem;
    font-weight: var(--font-weight-bold);
    color: var(--color-dark);
    margin-bottom: var(--spacing-sm);
}

.feature-description {
    font-size: 1rem;
    color: var(--color-text-light);
    line-height: 1.7;
}

/* ===================================
   FOOTER SECTION
   =================================== */
.footer-section {
    padding: var(--spacing-xl) var(--spacing-md);
    background-color: var(--color-dark);
    color: var(--color-bg);
    text-align: center;
}

/* Traceability: FUN-SOCIAL-001, FUN-SOCIAL-002 (Social icons) */
.social-links {
    /* Traceability: STK-FRONTEND-009 (Flexbox for layout) */
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

/* Traceability: FUN-SOCIAL-005, FUN-SOCIAL-006, FUN-SOCIAL-012 (Hover states, mobile clickable) */
.social-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--color-bg);
    text-decoration: none;
    font-size: 1.125rem;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: 8px;
    background-color: rgba(255, 255, 255, 0.1);
    transition: all 0.3s ease;
}

.social-link:hover,
.social-link:focus {
    background-color: var(--color-primary);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(255, 107, 53, 0.4);
}

.social-link i {
    font-size: 1.5rem;
}

/* Traceability: FUN-SOCIAL-011 (Text fallback) */
.social-label {
    font-weight: var(--font-weight-bold);
}

.footer-copyright {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.7);
    margin-top: var(--spacing-md);
}

/* ===================================
   RESPONSIVE DESIGN
   =================================== */
/* Traceability: FUN-LAYOUT-005 (Mobile viewports < 768px) */
@media (max-width: 767px) {
    .hero-section {
        min-height: 90vh;
        padding: var(--spacing-lg) var(--spacing-md);
    }
    
    .product-name {
        font-size: 2.5rem;
    }
    
    .tagline {
        font-size: 1.25rem;
    }
    
    /* Traceability: FUN-FEATURES-008 (Mobile grid) */
    .features-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
    
    .social-links {
        flex-direction: column;
        align-items: center;
        gap: var(--spacing-md);
    }
    
    .social-link {
        width: 100%;
        max-width: 300px;
        justify-content: center;
    }
}

/* Traceability: FUN-LAYOUT-006 (Tablet viewports 768px-1024px) */
@media (min-width: 768px) and (max-width: 1023px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Traceability: FUN-LAYOUT-007 (Desktop viewports > 1024px) */
@media (min-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* ===================================
   ACCESSIBILITY
   =================================== */
/* Focus visible for keyboard navigation */
a:focus-visible,
button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Reduced motion preference */
@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
    
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ===================================
   PRINT STYLES
   =================================== */
@media print {
    .hero-section {
        min-height: auto;
        background: white;
        color: black;
    }
    
    .product-name {
        -webkit-text-fill-color: black;
        background: none;
        color: black;
    }
    
    .social-link {
        background: none;
        color: black;
        border: 1px solid black;
    }
}